Note: Descriptions are shown in the official language in which they were submitted.
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Background of the invention
Field of the invention:
The present invention relates to broadband information transfer through optic
fibers,
and more specifically to a System and method for transferring much more
information
in optic fiber cables by significantly increasing the number of fibers per
cable and/or by
using multiple cores per each fiber, for example by using preferably flatter
fibers, each
with multiple hollow cores, each core preferably surrounded by smaller tunnels
that
create a light band-gap around each such core (which enables much better
reflection).
In order to enable this, the present invention solves various mechanical,
optic and
electronic problems that are created by stacking much more fibers in the same
space.
Back rg ound
With the current explosion of information transfer, optic fibers are becoming
faster all
the time. Most of the recent advances in the amounts of data that these fibers
can carry
per time unit have come from adding more and more wavelengths (termed
wavelengths) to the same fiber at the same time, a method which is called DWDM
(Dense Wave Division Multiplexing). The biggest obstacle to this was the lack
of
suitable amplifiers, until the Erbium amplifiers were discovered in the late
80's, which
have 2 advantages: 1. They don't need to convert the optical signals to
electricity and
back, but instead, light in the feeble input signals stimulates excited Erbium
Atoms to
emit more light at the same wavelength, 2. Because they preserve the
wavelength of the
optical signals, they can amplify many wavelengths simultaneously without
having to
first extract them separately and then recombine them after amplification.
However, use
of DWDM has been utilized only in the last few years. Today a single optic
fiber can
carry up to 80 or even 160 different wavelengths simultaneously, and the
number is
likely to increase further. The fastest bit-rates achieved so far per each
wavelength are
around 10 or 40 Gigabit per second, but it will be hard to go much beyond
this, since
higher bit-rates have much lower tolerance to dispersion problems. Therefore,
the
present wisdom concentrates mainly on trying to increase the number of
wavelengths
per fiber. The upper limit per optic fiber using the present methods is
currently
estimated to be around 100 terabits per second, and is expected to be achieved
within
the next 8 years.
However, The demand for broadband communications, fueled mainly by the
Internet
growth, is still growing by a much faster rate than the growth in the
abilities of optic
fibers. Typically, this demand has risen in the last few years by a factor of
up to 5-fold
each year, and this demand will probably continue to grow, as more people join
and as
users want to use heavier applications, such as for example Video, 3d, virtual
reality,
and so on. For example, many of the Trans-Atlantic submarine cables laid in
the last
few years were designed to satisfy demands for a number of years, but were
fully used
up (fully subscribed for) almost before their installations were finished.
Trying to
condense for example more wavelengths in each fiber is expensive and advances
are
not fast enough. On the other hand, other avenues for giant leaps have not
been
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explored enough yet, and one of the things that can be tremendously improved
almost
instantly is the number of fibers per cable, a fact which the "current wisdom"
seems to
ignore at present. Typically, submarine cables each contain only 4-8 actual
optic fiber
pairs, or at most 16 pairs (in each pair one fiber typically transfers
information in one
direction and the other fiber in the other direction). This is a very small
number and
demonstrates some kind of myopia or fallacy in the prior art in this area.
There are
already about 300 such submarine cables around the world, and also a large
number of
land cables, so the current wisdom seems to be laying each time a cable with
just a few
optic fiber pairs, and then laying a new cable each time it is used-up. As
will be shown
below, this is very wasteful, apart from the fact that it is also less
desirable ecologically
(since submarine cables can damage for example coral on the sea floor, etc.).
It is true
that until the erbium amplifiers started to be used, adding more fibers to the
cable was
very expensive, because very expensive electro-optical repeaters were used,
which
converted the optic bits to electricity and after amplification back to
optics. Each
repeater station of this kind was able to handle only very few fibers, and
adding more
fibers would make it much more expensive. However, since the TAT-12/ 13
submarine
cable (TAT stands for Trans-ATlantic), which entered service in 1996 and
started using
the Erbium amplifiers, this problem is now smaller. Yet, the "conventional
wisdom" in
this area has still not considered yet the possibility and implications of
adding much
more fibers per cable. Although there are indeed still problems involved in
doing this
even with Erbium and/or Raman amplifiers, the present invention tries to solve
these
problems in a very cost-effective way.
Summary of the invention
The present invention tries to achieve a large leap in thinking in this area
by trying to
explore dimensions that haven't been explored sufficiently by the "present
wisdom".
The main embodiments of this concept discussed in this patent request are
trying to
transfer much more information in these cables by putting much more fibers per
cable,
such as for example even 1,000 or 10,000 times more than what is being done
today.
One of the elements that seem to be most in need of improvement, is the number
of
fibers in each cable. Considering the high cost of the external metal shield
of submarine
cables (typically about $20 per meter) compared to the very cheap price of the
fibers
themselves (typically just a few cents per meter for a group of fibers), and
the fact that
long distance fibers are typically extremely thin (typically with a core of
about about 6-
micron, which is about 10-15 times thinner than a human hair), and considering
the
fact that the metal pipe size is usually about 2.5-5 centimeters in diameter,
it follows
that even if the internal diameter of this metal pipe is only 1 centimeter
wide, a much
larger number of fibers can be put in each cable - for example 1,000 or even
10,000 and
still there will be a lot of free space in the metal pipe. (A diameter of 1
centimeter,
which is 1/100 of a meter, is a thousand times larger than 10 micron, which is
1/100,000 of a meter, so given the square of it, even a few hundreds of
thousands of 10
micron fibers can be put together there). However, in the prior art long
distance optic
fibers have a much thicker cladding, so that the total diameter of the fiber
is usually
either around 125 micron or around 80 micron. Of course the 80 micron fiber is
better
than the 125, since it takes up less space and also has a considerably lower
bending
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loss, so today the trend is to move from 125 micron fibers to 80, and today
there are
even 40 micron fibers starting to be available. Theoretically the cladding
thickness
should be at least around 10 times the wavelength in order to keep the losses
at
minimum, so for example when using light wavelengths around 1550 nm a cladding
thickness of about 15 micron on each side is more or less the minimum for
avoiding
increase of losses, and also in order to avoid losses due to tunneling, the
minimum
required cladding thickness is approximately around 12 micron, so this
thickness is
again close to the minimum. Therefore, the new 40 Micron fibers seem to be
near the
minimum for the normal type of core and cladding materials. But even so, for
example
with a coating thickness of for example 1 micron or for example a few microns,
or even
for example a few dozen microns (preferably made of some flexible, preferably
strong
material, preferably polymer), or any other thickness lower or considerably
lower than
for example 75 micron (the usual diameter of the standard 125 micron fibers is
around
250 micron together with the coating, which means a thickness of around 62.5
micron
on each side), much more fibers can be packed together. For example if the
coating
thickness is 10 micron on each side, then the 40 micron fibers (10 micron core
+ 15
micron cladding thickness on each side) will have altogether a diameter of 60
micron.
So for example in 1 square mm for example there can be 256 such fibers, and
for
example in 1 square cm there can be for example 25,600 such fibers, and for
example if
the internal diameter of the pipe is even just 2 cm, then these 25,600 fibers
would
occupy less than 25% of the space, so most of the remaining space can
preferably be
used for allowed movement to compensate against stress caused by the bending
of the
cable. However, usually the pipe has a diameter of around 5 cm, so it has even
much
more available space than that, since with such a diameter the inner space can
be for
example near 15-20 square cm). However, by preferably using for example holey
fibers, for example with wavelengths of around 200 nano and/or less (extreme
UV), the
minimum cladding required would be around 2 microns on each side (and the
tunneling
distance should also be reduced proportionally), so for example with a core of
around 1-
2 micron with such frequencies and a cladding of for example 2 microns on each
side,
each fiber can have for example a diameter of 4 micron, and for example with a
coating
of 2 microns thickness on each side, the entire fiber can have for example an
outer
diameter of 10 microns. Similarly, for example if the wavelengths used are
between
200-400 nm, the fiber can have for example a holey core of 2-4 microns and the
cladding can be for example 4 microns on each side, so for example with a 5
micron
coating thickness the fiber can have an entire diameter of around 25 microns.
Or for
example the wavelength is for example 200-700 nano and thus the cladding is
for
example of 7 micron in thickness on each side, and for example the core is 4-5
microns,
and the coating is for example only 3 micron on each side, so altogether the
fiber would
still have a total diameter of around 27 micron. Or for example the
wavelengths used
are for example up to 1000 nm, for example with a core diameter of 3-8 micron
and for
example a cladding of around 10 micron thickness and a coating of for example
5 or
less micron thickness on each side (or for example 3 microns), thus reaching a
total
fiber diameter of for example 30-38 micron. This means for example that 1
square mm
of closely packed 25 micron fibers can contain around 1600 fibers. As
explained below,
by using for example flat multi-fiber jackets and/or for example multi-layer
structures,
the coating can be reduced even further, since for example the coating layer
between
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each two adjacent fibers in the flat jackets can be for example a few microns
or even
less, for example even 1 micron or less, and the flat jacket's thickness can
be for
example 1 or a few microns (or more) more than the diameter of the fiber. The
jacket
can be or example created simply by laying the fibers side by side without
coating and
then coating them together, or for example first coating each fiber for
example with a
coating layer with a thickness of for example 1 or a few microns or more, and
then for
example laying them side by side and coating them together. However, since the
optic
fibers are normally created by drawing and the cladding is typically added by
vapor
deposition, for example a group coating in the form a flat jacket can be for
example
added in a similar way or for example through dipping in some solution and/or
for
example by extrusion and/or for example by gluing the fibers as they are being
pulled
side by side between two jacket surfaces, and preferably this is done while
the fibers are
being pulled together side by side, for example in a production line. The
gluing has an
advantage that if used with the proper materials the mechanical strength of
the jacket
transfers better between the fibers.
Also, it should be taken into account that the materials themselves are not
the only
cost in laying such a cable. For example, the work involved typically costs at
least
about 15% of the entire operation. So putting much more fibers in each cable
is actually
even more cost-effective. Also, it must be understood that the substance the
optic fiber
itself is made of - silica - is actually one of the cheapest and most
available substances
on earth, so as more and more such fibers are mass produced, their price will
probably
keep dropping even further. So, for example, if we put 10,000 10-micron fiber
pairs in a
single cable instead of only 8 pairs, and assuming that 8 pairs cost for
example 5 cents
per meter, the cost per meter will rise from $20 to $82.5 (1,250 times more
expensive
per meter of fibers is $62.5 instead of $0.05). But this is only about 4 times
more
expensive than before, whereas compared to 8 pairs, we have now 1,250 times
more
pairs, so we have a 1,250 times wider bandwidth. This example shows that it is
indeed
tremendously more cost-effective, since, assuming for example that much more
companies will want to be a partner in such a venture and buy-up small parts
of it, the
total price per participant company will be much cheaper than today. And when
using
this in overland cables, the huge jump in price-performance is even much
higher,
because the external pipe can be thinner and cheaper. Also, when used for
example in
metro areas to create connectivity within and between large cities, typically
no or few
amplifier stations are needed, so the price-performance of adding much more
fibers can
be even higher. This can also make the Internet usage much cheaper to the end
users, so they will have both a much faster Internet and much cheaper access.
So
unlike the normal advances in this area, which typically today double the
bandwidth each year, the present invention allows for a giant leap of for
example
1,000 more bandwidth, that can be produced today, and with a much smaller
increase in cost. This new approach can be called for example Dense Fiber
Multiplexing. The present operations of laying optic fiber cables all over the
world
are similar to the opening up of the American West by the railways in the 19th
century, except that with the current invention we can lay an almost infinite
number of "railways" within a very small space. And since DWDM will also
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probably continue to advance (although at a slower rate) and put more
wavelengths into each fiber, the total growth of combining all of this is
gigantic.
There are a number of problems that have to be solved in order to make this
breakthrough possible:
1. First of all, we have the problem of maintenance. Arguably, such a large
number of
fibers in each cable will make it much harder to maintain their integrity. But
there
are a number of solutions to this: First of all, ever since Erbium amplifiers
replaced
the bulky electro-optical repeaters that existed before, the entire system is
much
more reliable, so that the typical 8 pair cable usually needs only about 1
repair per
25 years. It is true, however, that having for example a 1,000 times more
pairs also
increases by the same proportion the chances for malfunctions. But such a
system
has so much spare room that is should indeed be enough for many broadband
providers for many years, so that even if, for example, half of the fibers in
this new
concept become damaged, the other half will still be enough for quite a long
time,
even if no repair is done. In other words, there is an additional shift here
compared
to the prior art in this area, in that we rely much more on the statistics of
how many
fibers in absolute numbers still remain operational, instead of relying mainly
on a
small chance for a malfunction over a period of time, and repairing it
whenever it
happens. However, preferably the system includes also mechanisms for detecting
malfunctions as soon as they occur and automatically assigning other fibers
instead
of the malfunctioning fibers.
2. Secondly, with such a large number of fibers the problem of how to identify
each
fiber at both ends of the line becomes much less trivial than for example when
only
8 pairs are involved. One solution is for example to mark each fiber with a
distinct
mark, but this is not so practical. Another solution is to preferably group
them into
smaller groups, for example by wrapping each group with a separate plastic
jacket,
and marking the jackets for example with a separate color. So, for example, if
10,000 pairs are used, they can be grouped for example into a 100 groups of a
100
pairs each (or for example with separate groups for each direction). This
makes the
mission of locating matching fibers at the two ends of the cable much easier.
Another solution is to hook up all of the fibers to an array of numbered
sensors
connected to a computer at each end of the cable and then let the two
computers
communicate and start testing automatically serially each fiber by sending a
signal
through it from one computer and registering on which sensor it came out at
the
other end. This way, the two computers can very quickly create a translation
table
that documents which element on each side corresponds to which element on the
other side, but this is much less efficient. A much better solution is to use
multi-fiber
flat jackets, as explained below (it is also possible to mark for example by
separate
colors or lines subsections on the jacket). Of course, various combinations of
these
solutions are also possible.
3. Thirdly, if for example a cable between the USA and Israel cannot be laid
in one
run, than a "stitch" in mid-ocean is needed, and this becomes much more
difficult if
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you have for example 10,000 optic fiber pairs instead of only 8. The answer is
that,
first of all, there is usually no such problem, because the ships that install
these
cables are capable of laying thousands of Kilometers of consecutive cable in
one run
(typically such a cable for example between Israel and the USA can be laid in
one
run, taking about one month to do it). If for some reason a much longer cable
was
needed without a stop on land, then this can still be solved for example by
using a
larger ship, that can still carry the entire cable in one run, or using for
example a
group of ships that are connected for example mechanically in a way that
enables
them to carry together a larger consecutive cable, or using a cable of smaller
external diameter. If the smaller cable is less strong, this can be solved for
example
by using stronger material, or using for example some rings of stronger
material
embedded every once in a while in the shell of the cable. Another possible
variation
is to use at sea preferably an automatic fiber-welding machine that can weld
two
fibers as if they were made in one piece in the factory, although this is more
expensive and will slow down the laying process by the time needed to "stitch"
so
many fibers, so for example if it takes the machine a whole month to weld
20,000
fibers, and 4 such breaks are needed, then it slows down the laying of the
cable by 4
months. Also, such stitching might for example degrade a little the
performance of
some of the fibers, so this solution is less desirable (however, usually it is
not more
than 1 dB degradation). Another solution is to use for example a water-proof
protective shield of smaller external diameter so that much more cable can fit
on
each wheel, and then preferably add dynamically an external stronger shield
which
for example comes open and can be externally added to the cable from around it
and
preferably be sealed automatically during the process of laying the cable.
Another
solution is to use multi-fiber flat jackets with delta-type connectors that
connect for
example by pressure or by welding, as explained below. Of course, various
combinations of these solutions are also possible.
4. Another problem is that if there are much more fibers within the pipe,
there is more
danger that they will be damaged by friction or stress or movement against
each
other for example when laying the cable. Therefor, in one embodiment each
fiber is
coated by a very thin layer of low friction plastic that preferably does not
add more
than 1 micron or at most a few microns to the fiber's size. This coating is
preferably
with the same thermal expansion coefficient as glass, and can also be for
example in
different colors for groups of fibers, which is also good for the problem of
identifying the fibers at both ends, but is preferably opaque and dark at
least on the
inside, to absorb escaping photons. Preferably, also an anti-friction material
is added
into the pipe between the fibers, such as for example Talc powder or anti-
friction
gel. Another possible variation is to put the fibers in larger groups into
protective
jackets, so that for example we can have about a 100 plastic jackets, each
containing
for example about 100-200 fibers. Preferably, there is enough extra space
within
each jacket for the fibers to move freely sideways (and/or up and down) in the
jacket
in order to compensate for stress caused by bending of the metal pipe.
Preferably,
there is also enough inner space left between these jackets in the metal pipe
for these
jackets to move freely sideways (and/or up and down) to compensate for stress
caused by bending of the pipe. Another possible variation is suspending the
fibers
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within the pipe in a fluid preferably with specific weight close to that of
glass, so
that they float freely in the fluid and have less friction. Preferably this
fluid is also
dark and opaque to light, to avoid possible cross-talk between closely
touching
fibers and preferably this fluid also helps the pipe resist the pressure of
the external
water for example in case of a submarine pipe, so that this fluid can be for
example
even water itself or some water based solution. Another possible variation is
to give
the fibers an electrostatic charge so that they repel each other and thus have
less
friction, however it may be difficult to create and maintain this charge. (It
could be
done for example by applying a high voltage to the fibers at certain intervals
and
also to an electrically insulating inner coating of the pipe, so that the
fibers stay
away from each other and from the inner border of the pipe, and also the
fibers
should be loose enough so as to move relatively freely in response to stress
caused
by bending of the pipe. The electrostatic charge generated can be carried on
to long
distances and uses-up only a few watts. By keeping the electrostatic charge
not too
high, the fibers can stay relatively close to each other, but avoid contact,
since the
closer they get, their repulsion increases). Another possible variation is to
use
thinner fibers, so that if we use for example 1 micron fibers instead of 10
micron
fibers, they will have more room to move around the inner space of the pipe
(however, this would require, of course, using shorter wavelengths for the
signals,
as explained below). Another preferable variation is to use instead a flat
cable, so
that for example we have a cable 20 centimeters or even 1 meters wide and for
example 2 millimeters high (internally), and the fibers are lying relatively
flat or
completely flat across the width of the cable. Of course, many sizes are
possible. Of
course, in this case we need structural strengthening against the pressures
that exist
for example in deep sea, so we can use for example a wavy socket-like
structure
between the bottom and the top so that the fibers are in the gaps between the
"waves" (and each socket contains for example 1 or dozens or hundreds of
fibers),
or a cell-structure, so that in each cell are a certain number of fibers and
the cell
walls support the flat cable from being further flattened by the pressures.
The flat-
cable solution also makes another very good solution to the problem of
identifying
the individual fibers. In each cell the cables or groups of cables can also
have some
protective coating. In all of the above solutions, preferably the fibers are
loose
enough so as not to accumulate too much tension when the pipe is curved.
Another
possible variation is to use, preferably together with a flatter metal pipe, a
multi-
fiber flat, preferably flexible, jacket for the fibers (each containing for
example
1000-2000 fibers), so that for example a number of such jackets can be stacked
upon
each other in the pipe and the pipe has one cell or a number of cells side by
side, and
preferably the fibers can move freely up and down within the flat jacket to
compensate for stress caused by the bending of the pipe, and preferably also
the flat
jackets themselves can move similarly up and down within the pipe. Also, the
flat
jackets preferably have the same thermal expansion coefficient as glass.
Another
possible variation is a preferably flexible, multi-layer, structure that fits
preferably
in a somewhat flattened pipe, and also preferably allows each fiber to move
freely
up and down within its "mini-cell", and preferably the structure itself can
also move
at least up and down in order to compensate for stresses. Another possible
variation
is using for example one wide flat jacket for all the fibers and rolling it up
within the
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pipe. These various exemplary configurations are described in more detail in
Figs.
lOa-d. These flat jackets or multi-layer jackets are preferably made of for
example a
plastic low friction material. These flat jacket solutions and multi-layer
solutions
also make it much more convenient to identify the fibers at the two ends of
the
cable, and can also make it easier to create preferably modular group-
connectors at
the two ends of the cable. Preferably, this can also make it easy to create
modular
interfaces at the amplifiers, which can be used with the various solutions
described
for the amplifiers. (It can also help for example to keep the fibers away from
each
other at the amplifier in the solution of Fig. 8, by creating a small gap of
fibers
stripped from the jackets or from the structures and putting the jackets at
even
distances from each other, so that the jackets on the two sides of the gap of
bare
fibers keep them in position, and the laser pump beam can hit all of them at
the
same time). Another possible variation of the pipe that can be used with these
flat
jackets is for example a double pipe made of two (or more) for example hexagon-
shaped pipes with a shared plane between them, or for example two (or more)
round
pipes welded together side by side. These structures have great structural
strength
and make sure that the set of pipes will bend only in one direction, however,
in both
of these variations each of the two (or more) cells are preferably wider than
high, so
that the width of the flat jacket is greater than the height of the cell, in
order to make
sure that the flat jackets always keep their correct orientation in relation
to the pipe.
So preferably either the pipes are still somewhat flattened, or they are round
externally but somewhat flattened in their internal space. If the shapes of
the 2 or
more pipes remain round and not flattened internally, then one way of keeping
the
flat jackets in the correct orientation is for example to add an elongated
square cell
in the middle in which the flat jackets reside, and then the top and bottom
remaining
empty spaces can be used for example for electrical wires. This configuration
is
shown in Fig. 12. Other variations in the shape of the pipe are also possible.
Another
possible variation is to put one or more small dense bundles of fibers, each
bundle
preferably in one jacket, in the pipe, so that the bundles can move freely.
For
example, a bundle of a little more than 1mm in diameter can contain about
10,000
densely packed 10-micron fibers. However, packing fibers together at distances
of a
few wavelengths of the light can cause cross-talk between the fibers.
Therefore,
another possible variation is to combine this with a very thin coating of
flexible
preferably opaque material (such as for example plastic, or nylon, or other
polymer,
or paint, or anodization of metals, etc.), over each fiber, which is
preferably black or
dark at least on the inside in order to absorb escaped photons and is
preferably with
the same thermal expansion coefficient as glass, or immersion in an opaque
dark
liquid or powder (such as for example fine carbon powder). If a coating is
used,
another variation is preferably to add also slight gaps in the coating or more
than
one coating material intermittently, preferably with slight gaps, to
compensate for
thennal expansion problems if the thermal coefficient is not close enough to
that of
glass. This coating can be also on the outside at least partially marked with
a
different color for each sub-group of fibers. If a powder or liquid is used,
another
possible variation is to use also an electrostatic charge to improve the
dispersion.
Also, sub-groups of fibers can be grouped for example into preferably very
thin
group-jackets within the larger jacket - for further strengthening and easier
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identification. This is less efficient than the flat jacket solution since
there is no
directional optimization, but it still may enable using quite a large number
of fibers.
Of course, like with the flat jackets, this may work even better with thinner
fibers,
such as for example a few microns or 1 micron. It is important to emphasize
that
the multi-fiber flat, preferably flexible, jackets are very different from the
"current wisdom" types of optic-fiber jackets, and so are the multi-layer
structures that are suggested, and also the for example the flattened metal
pipe
(with or without a division to inner cells) and the structure of 2 or more
welded
pipes, and the combination of flat jackets moving freely up and down only in
the desired directions in the special pipes, which can bend only in the
desired
directions, are very different from the round pipes used in the prior art. Of
course, various combinations of these solutions can also be used.
5. The biggest problem is again the amplifiers. Eventhough this problem is
much less
severe than it would have been with the old electro-optical repeaters, it
still requires
considerable adaptations to enable the Erbium amplifiers to efficiently deal
with a
much larger number of fibers. Typically these amplifiers are needed about
every 80-
120 Kilometers, so, for example, for a cable between Israel and the USA (about
7,000 Kilometers), about 70 such amplifiers are needed. The state of the art
Erbium
amplifiers typically work around about 10 meters of fiber that have been doped
with
Erbium atoms as an impurity during the manufacturing process of the fiber. At
the
area of the amplifier, a "laser pump" is used to excite the Erbium atoms and
make
them increase the strength of the feeble signals. This is done in the current
state of
the art by supplying electricity to a laser at the amplification area, which
has to work
with coherent light and at a certain frequency which is close to the range of
frequencies of the wavelengths used in the fiber, but not too close, so as not
to
disrupt the signals. The light from this laser "pump" is then optically
coupled to
each of the fibers, typically by the use of optical splitters. Typically, for
example, in
a 10 meter section of erbium-doped fiber, a pump wavelength of 980 nanometers
or
1480 nanometers provides about 2.2 dB/milliWatts of amplification (Overall
amplification saturates around 25-30 dB). So the cable contains also
electrical
wiring for supplying the electricity to the laser "pumps". Another new type of
amplifier that is just beginning to be used is a Raman Amplifier, which works
similarly to the Erbium amplifier, except that no Erbium impurity is needed in
the
fiber, so that it can work with ordinary optic fibers. It also uses a similar
laser pump
to boost the signal energy, but has the advantage that instead of a 100
nanometers
range where Erbium is most sensitive (roughly between 1500 and 1600
nanometers), the Raman amplifier can work with a 200 nanometers range, and
also
unlike Erbium, which has this 100 nanometers band at a fixed position, the
Raman
amplifier can shift the 200 nanometers band to any position, so that a number
of
amplifiers can be used each with a 200 nanometers shift compared to the
previous
one, so altogether a much larger range can be used and therefore a larger
number of
wavelengths can be used (since there is a minimum separation needed between
each
two adjacent wavelengths). It also makes better separation between the signal
and
the noise, compared to Erbium amplifiers. The only disadvantage it that it
requires
higher energy (higher pump powers) for achieving the same effect. But it will
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probably gradually replace the Erbium amplifiers. Typically, at the area of
the
amplifier, the pipe becomes larger, in order to accommodate the laser pump or
pumps and the interface required for it. Anyway, whether using Erbium
amplifiers
or Raman amplifiers, or other laser pump or similar technologies that will
exist in
the future, making arrangements for powering for example 10,000 fiber pairs
instead
of just 8, is still problematic, and requires sophisticated solutions in order
to be cost-
effective. A number of solutions to this major problem are described in the
detailed
descriptions of the preferred embodiments below (Of course, over small
distances,
such as for example within a single town or between close towns, no amplifiers
are
needed at all, so this problem does not exist at all):
a. Using a much larger number of small-power laser pumps of the type used
today, each supporting only one or a small number of fibers, preferably in
multi-pump chips connected to multiple fibers. (When nanotechnologies
become available, as explained below, this might become even cheaper and
more convenient). The power requirements for the amplifiers will of course
be multiplied by the number of laser pumps added at each amplifier station.
b. Using a more powerful laser pump (or pumps) that is capable of amplifying a
much larger number of optic fibers, and using various possible methods to
distribute this energy to many fibers. Depending on the implementation, this
can save for example a lot of expenses on opto-couplers and on the overhead
of having to deal with a separate amplifier for each fiber. If we multiply for
example the number of fibers 1,000 times more than the numbers used in the
prior art, this pump needs of course about a 1,000 times more power, so, if
for example 12 milliwatts are needed for a single Erbium doped fiber, than
we need now about 12 Watt - still quite reasonable. Another problem is that
with powerful lasers it might be difficult to get exactly the needed frequency
for the Erbium, since various limitations limit the available frequencies.
Therefore, another possible variation is to use for example Raman amplifiers
instead, so that more flexibility is available. However, a bigger problem is
the
higher signal attenuations if other less optimal frequencies are used, because
the laser pump can typically only amplify signals which are at wavelengths a
little longer than it, so, for example, if the closest powerful lasers work at
1064 nanometers, the signals would have to be for example at 1100-1200
nanometer, which have considerably more losses than for example around
1550 nanometer. There are a few solutions to this: 1. Try to create powerful
lasers in more optimal frequencies, for example by mixing various gases used
for creating the lasers. 2. Use a combination of two or more lasers, for
example, since there are for example powerful Nd:YAG lasers available at
1064 nanometers and at also at 532 nanometers and 355 nanometers (by
frequency multiplication), combining the light from both types and
preferably filtering out the noises created by the combination, can create a
laser of 1596 nanometers or 1419 respectively, or mixing it with other lasers
of the visible spectrum (such as for example Helium-Cadmium lasers, which
are typically available at 325-442 nanometers, Xenon-Fluoride lasers, which
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are typically available at 353-459 nanometers, or Argon lasers, which are
typically available at 457-528 nanometers) can achieve other desired
frequencies (however this has also a price of some reduction in the pump
power). However, since these types of lasers typically have low efficiencies,
it is better to use for example grouped diode lasers - some are available for
example with powers of 50 up to 2000 watt, or quantum-cascade lasers,
which can give high-efficiency in almost any desired frequency in the near
infra-red range (750-2600 nanometers) and mid infra-red. 3. Use for example
interferometric wavelength converters, or a series of Raman amplifiers to
shift the laser frequency higher in one or more steps by strongly amplifying
each time a signal of longer wavelength with the laser pump, and then using
the amplified signal as the new amplification pump. 4. Use fibers with lower
losses at the other frequencies. For example, since the main cause of
Rayleigh scattering is inhomogenities caused by fluctuations of glass density
and compositions, producing more homogenous fibers will probably reduce
this, so that signals can be used for example at the range of 1100 nanometers
and above with the laser pump of 1060 nanometers. Also, It might be
possible to add some materials to the glass that will reduce its losses at
these
frequencies. for example ZBLAN fibers (which contain Fluoride, Zirconium,
Barium, Lanthanum, Aluminum and Sodium) can work at ranges such as
1300-4000 nanometer with attenuations as low as 0.001 dB/Kilometer.
Another possible variation, discussed below, is using holofibers (holey
fibers), preferably with an optical band-gap of smaller tunnels around each
tunnel, so that the optic signals travel through free air, and so there is a
much
larger range of frequencies available and much smaller attenuation. 5. Use
some combination of the above.
c. Use some combination of the above 2 possibilities, for example a number of
such lasers, each powering a subset of a large number of fibers.
However, the power requirements for the laser pump (or pumps) might become
problematic if we take into account the fact that the laser efficiency is
typically
relatively low (although there are considerably large variations in efficiency
between
various types of lasers as explained above), so we have to multiply the
previously
mentioned power by the laser inefficiency factor, and taking into account the
fact that
for example on a cable between Israel and the USA approximately 70 amplifiers
might
be needed, the total amperage needed might be quite high. This is problematic
because
we then need a thicker electrical wire, which can fill-up too-much of the
inner space of
the pipe. This could be solved by making the pipe of the cable thicker, but
this would
make it more difficult to lay the cable in a single run, so this is the least
desirable
solution. We could also use for example a separate power cable running along
the optic
fibers cable, but this is also a very expensive solution so this also is less
desirable.
There are a number of better solutions for this problem:
a. Use higher voltage for carrying the electrical power, which means lower
amperage
and less thickness needed for the electrical wires. However this can only be
done till
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a certain limit, otherwise a too high voltage can cause problems of electrical
leakage, especially when submarine cables are concerned. Preferably, the
amplifier
areas contain also appropriate transducers for converting the electrical power
to the
correct voltage needed for empowering the laser pump or pumps. Preferably this
is
combined also with better insulating layers.
b. Use a multiphase electrical power (typically 3 phases are the most
efficient, and 3
power lines are needed for this instead of 2).
c. Since the metal shielded pipe of the cable is itself a bulky element, we
can take
advantage of it and make this problem part of the solution by using more than
one
layer of metal for this shield with good electrical isolation between them, so
that for
example part (or parts) of the metal pipe itself is used as both a
strengthening shield
and as electrical power lines. Preferably the shield itself is made mostly of
material
with the same thermal expansion coefficient as glass, but since such alloys
might
not be the best electrical conductors, we might need to use for the electrical
conducting layer materials with a different thermal expansion coefficient.
Therefore,
preferably these conducting layers are surrounded by flexible electrical
insulators,
such as for example sponge, so there is enough space to accommodate the
different
thermal behavior of these layers and for the fact that they can warm up more
because of the electrical current. Preferably, these layers can also be made
for
example somewhat wavy or mesh-like (but still preferably with a big mass) in
order
to compensate even better for this different thermal behavior. This can be
done both
in a round cable and in a flat cable.
d. If a cable with more than one cell is used, the electrical wiring can also
be inserted
for example as an isolated layer within the support wall or walls that are
between
cells.
e. Use some external power source at the amplifiers, instead of or in addition
to the
electrical power lines. This can be very easily done in overland cables, and
at sea for
example geothermic energy might be used, or solar energy, conducted form
above,
or energy from water currents, or other forms of energy.
f. Use electrical wires made from the newly discovered carbon nanotubes, which
can
now be created from graphite in mass-quantities. Wires made from these
nanotubes
(for example Bucky tubes) will have a conductivity 10-100 times higher than
copper, and will be about a 100 times stronger than steel and 4-10 times
lighter and
much more flexible and endurable. Also, adding for example a certain amount of
Alkali metal atoms can make them super-conductors. This could also be a good
combination for example with solution c, and, in fact, the entire pipe of the
cable (or
at least some parts or some layers of it) might be made from insulated layers
of this
material (or some hybrid with this material) - as soon as the material becomes
cheap
enough to compete with steel. This will enable us to use a pipe with smaller
external
thickness that will be much stronger than the current pipes, and therefore
also solve
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the problem of laying cables for longer distances consecutively without any
stitches
needed on the way.
g. Use fibers with lower losses, such as for example ZBLAN fibers, which can
work at
ranges such as 1300-4000 nanometer with attenuations as low as 0.001
dB/Kilometer, an/or for example holofibers (holey fibers), which means that
much
less amplifiers are needed on the way.
h. Use various combinations of the above solutions.
These improved amplifiers, although definitely more expensive than normal
state of
the art amplifier stations that have to deal with just a few fiber pairs, are
still just a
small ingredient in the cable. So if for example a normal submarine cable
between
Israel and the USA costs about 250 million Dollars ($20.1 per meter x -7,000
Kilometers, plus some additional expenses) and a similar cable based on the
present
invention costs about 800 million dollars, then even if each of the
approximately 70
amplifier stations costs an extra 1.5 million dollars, it will still be just
around 900
million dollars for the entire cable.
6. However, another related problem to the amplifiers problem is the fact that
even
with Erbium or Raman amplifiers, Regeneration Repeaters are still needed after
certain distances in order to restore the shape and timing of the signals,
mainly due
to chromatic dispersions (caused mainly by the impurities of the wavelengths)
and
polarization dispersions (caused mainly by asymmetries of the fibers). Having
to
add regenerators can significantly increase the costs, since electro-optical
regenerators are used for every wavelength in every lit fiber. Until recently,
for
example Erbium amplifiers were needed every 80-120 km, and regeneration was
needed typically after 600 km. However, recent advances are beginning to solve
this
problem and have successfully transferred already DWDM signals over 6400 km
without regeneration, and longer distances of 8,000 km and even above 10,000
are
also expected soon. Corvis Corp. for example has accomplished this by using a
combination of Distributed Raman amplifiers (which use the fiber itself as the
gain
medium, so the signal weakens much less over long distance) together with
Soliton
technology that gives the pulses a special shape that causes their shape to
regenerate
itself periodically automatically after certain distances. Qtera (bought by
Nortel),
also uses a similar Soliton technology, together with Erbium amplifiers. Xtera
will
use a combination of distributed and discrete Raman amplifiers. Marconi
(bought by
Cisco) has accomplished this, again, by Soliton technology. Optimight is doing
it by
adding Code Division Multiplexing and using higher power lasers. In addition
to
this, other solutions are improving Error corrections by better redundancy FEC
(Forward Error-Correction) Codes, such as for example Ciena is doing. Another
solution is for example correcting the Polarity Mode Dispersion by DSP-
controlled
compensation upon entering the receiving end, as offered for example by Yafo
and
by Vitesse. Another solution is fibers with better chromatic dispersion
compensation
(for example by dispersion slope matching) and/or using more precise lasers
(for
example by better filtering of each wavelength). Another solution can be
optical
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filtering combined with the optical amplifiers, so that weakened distortions
can be
deleted. Of course, various combinations of these solutions will probably work
even
better. Another solution is using for example ZBLAN fibers, which have much
lower attenuation, as mentioned above, when they become cheaper. Another
solution (shown by Alcatel) is that if and when repeaters are eventually
needed, the
regeneration can be done optically for example by using SOA (Semiconductor
Optical Amplifiers), such as for example a Mach-Zehnder interferometer for 2R
regeneration (Reshaping) (because of its non-linear response) and two of these
in a
cascade for 3R regeneration (Reshaping & Retiming). However, the disadvantage
is
that for this regeneration the wavelengths still have to be separated and then
recombined and each wavelength needs its own repeater. Another possible
variation
is using holofibers, which have much less attenuation and much less
distortions
since the optical signals travel through free air. Another possible variation
is to
design holofibers in which there is a vacuum or reduced air pressure
(preferably in
combination with a vacuum or reduced air pressure throughout the solid cable,
so
that there are no forces that can crush the fibers). Of course various
combinations of
these and other solutions can also be used.
7. Another problem is the price of the lasers at the end stations. Since this
equipment is
still relatively expensive, few companies will be willing to invest in advance
for
example in 1,000 fibers, together with 1000 sets of DWDM lasers. However,
prices
of these lasers will probably continue to go down considerably in the next few
years,
so for example more and more fibers can be activated gradually on a need
basis. But
even now, no matter what the price of the end-station equipment is, it is
still much
more wasteful to have to lay a whole new cable after the small number of
fibers
have been used up. One possible solution that might help lower the price of
DWDM
lasers and/or increase their accuracy is to use for example an optically
diffractive
prism, preferably with alternating opaque and transparent stripes, for
optically
splitting each laser to discrete sub-frequencies, and then preferably amplify
each
sub-frequency and modulate it on/off separately for example by using an
integrated
electro-absorptive modulator or Mach-Zehnder Modulator, or an external Lithium
Niobate modulator. This can convert each single less precise laser into a
group of
more precise lasers (in other words each laser can be used for creating a
number of
wavelengths simultaneously), as shown in Fig. 13. An even better solution is
to
optically duplicate each original laser beam preferably many times, and then
use
preferably separate independent on/off modulation on each of the new laser
beams
and send each into another fiber, as shown in Fig. 14. This way for example
each
original more expensive and precise laser can be used simultaneously to
independently send separate signals into a preferably large number of fibers.
Preferably the splitting is done after the filters that further purify the
beam, so this
saves also on the typically expensive filters. Preferably, groups of fibers
are coupled
to multi-laser chips by using flat mutli-fiber jackets and connectors, as
described in
Figs. 10, lOa-b & 1la-c. Another possible variation is that preferably the
connector
at the end individual fibers or for example the other connector that has to
connect
with the connector end in which the fiber terminates, preferably one of them
preferably has a shape like a widening hollow cone and preferably this cone
and/or
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the other connector that goes into it can flexibly bend in any needed
direction
(preferably in a limited range of angles so that it does not bend out of
orientation),
and/or for example move in a limited range, so that, even if the fibers are
not exactly
aligned, the connectors automatically adjust their position. Another solution
is for
example temporarily using CWDM (Course Wavelength Division Multiplexing) on
more fibers, which, at least currently, is cheaper than using DWDM on less
fibers.
Of course, various combinations of the above and other solutions can also be
used,
so that for example the wavelengths are first split this way into a larger
number of
finer sub-range wavelengths, and these sub-wavelengths are then multiplied
many
times and on/off modulated for example into each fiber (or for example into
each
tunnel in a multi-core holofiber).
Another variation is using, instead of the type of fibers that exist today and
conduct
mainly visible light and infrared light, much thinner nanofibers, which have 2
main
advantages: a. Much more fibers can be contained in the same space, so that
for
example if we use fibers with a diameter of a 100 nanometers (a 100 times
smaller than
micron), we can accordingly put more than 10,000 times more fibers than in the
previous solution (of using for example 10 micron fibers) in the same space,
or in other
words, 10,000 x 1,000 = 10 million times more fibers than what is being used
today. Of
course, the ratio will increase even further if we use fibers with a diameter
of a few tens
of nanometers or just a few nanometers. b. Secondly, using such thinner fibers
is
suitable for shorter wavelengths (if the fiber's thickness is just a little
more than the
wavelength it can also help contain the signal more efficiently) and therefore
eventually
much faster bit-rates and much more wavelengths, so that for example a fiber
with the
size of a few hundred nanometers or less will be especially suitable for
carrying for
example extreme UV (less than 100 nanometers) instead of visible light, and a
fiber
with the size of just a few dozen nanometers or even a few nanometers will be
especially suitable for carrying X-ray radiation (less than 1 nanometer).
Also, in
addition to or apart from using the holey fibers for this, other materials
instead of silica
(glass) might be used for this that are better suited for such frequencies,
such as for
example special kinds of artificially made saphires, etc. Preferably, larger
nanofibers
(for example those a few hundreds of nanometers thick) will be produced by
conventional methods, and smaller ones (especially nanofibers with the size of
just a
few nanometers) will be preferably constructed by nanotechnology methods,
which
means "from the bottom up" by adding molecules, instead of starting with
larger
structures and using relatively crude methods to press or corrode them into
the required
form. This has been included already in the PCT of 2001, upon which the
present
application is based as a CIP of 10/307,422. And indeed, in 2003, scientists
have
succeeded in creating optical nanofibers with a relatively good regularity and
a
thickness of around 50 nanometers, by first using a normal drawing process
under a
flame to create a 1 micron optic fiber, and then they used a 2 nd stage in
which they used
a tapered sapphire fiber with a tip diameter of about 80 nano to absorb the
thermal
energy from the flame and transfer it to the drawn fiber. Since they used a
light
frequency with a wavelength larger than the diameter, most of the light
traveled outside
the fiber in a sleeve of an evanescent wave (so that the air acted like the
cladding),
however due to insufficient regularity of the surface and/or surface
contamination the
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losses were vary large: at 633 nm the optical loss with a 190nm fiber was
about 1.7dB
per 0.1 mm - which is very high. However with a fiber diameter of 450 nm and a
wavelength of 633 nm and similarly with an optic fiber of 1000 nm and a
wavelength of
1550 nm only 20% of the light traveled outside and the losses were down to 0.1
DB per
0.1 mm, which is still very high compared to the loss of normal state of the
art optic
fibers, which is about 0.15 dB/Kilometer. (Nature, Vol. 426, Dec. 2003). So in
order to
improve the regularity of nano-fibers, and especially for example when drawing
holey
nano-fibers (which are more complex since they are typically created by
joining
together a group of hollow fibers and then drawing them together) and/or for
example
for more precision even in drawing for example normal holey fibers, one
possible
variation is to use for example infra red lasers to improve the even
distribution of the
heat, for example instead of or in addition so such a tapered intermediate
device. This
can be done for example by using laser frequencies in which the conductance of
the
fibers is much more poor than their optimum. Another possible variation is to
use for
example automatic sensors to sense the irregularities together for example
with means
of automatic vapor deposition to correct them and/or for example other
automatic
means to correct them preferably locally. According to another article -
http://www.opticsexpress.org/view file.cfm? doc=%24)%2C3)
IP%20%20%OA&id=%25 (%2C'%2BJ%2CX%20%OA, the best holey fibers currently
have an attenuation of around 1.2 dB/Km, which is caused by surface roughness
caused
by SWC (Surface Capillary Waves), and they show that with a few additional
improvements the losses will probably soon go down to the level of ordinary
fibers or
even lower. However, according to http://www.lightreading.com/docurnent.asp?
doc id=21449&~rint~true, the current state of the art in making holey fibers
is Km-
lengths of polymer-coated fiber with losses as low as 0.5 dB/km at 1550 nm for
index-
guiding fiber [BLazePhotonics Ltd., ECOC 2002]. This is still more than 3
times the
losses of ordinary fibers, but since Holey fibers can carry signals which are
2 orders of
magnitude stronger than what can be sent in ordinary fibers (since nonlinear
effects in
the core are negligible in the hollow core), preferably in holey fibers the
signals are
broadcast with sufficiently strong power so that little or no erbium
amplifiers are
needed. For example, if normally about 70 amplifier stations would be needed
between
Israel and the US, so for example when the losses of holey fibers go down to
near the
level of the losses of the current state of the art normal fibers (around 0.15
dB/Km) or
lower, then for example broadcasting signals which are initially for example
around a
100 times stronger means that the distance to the first amplifier can be for
example a
100 times longer, thus for example no amplifiers will be needed at all for
example
between Israel and the US. However, an increase of 100 times the power
increases the
DB only 20 times so probably 5 amplifier stations will still be needed in this
example,
but this is still much better then for example 70 amplifier stations. In
addition, since
holey fibers can transmit a huge number of lambdas and/or since a huge number
of
fibers can be used for example by the methods described in the present
application,
another possible variation is that various, preferably multiple, forms of
redundancy are
used, for example by broadcasting the same data stream in more than one
channel (for
example as multiple lambdas in the same optic fiber and/or in more than 1
fiber), and/or
for example by adding more error correction data, so that even if the signals
arrive
weaker they can still be reconstructed with the help of the redundancy data.
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These nanotechnologies will preferably also enable us to create small nano-
lasers for
creating the wavelengths and for the pumps to power the amplifiers or at least
make the
interface for reaching each individual fiber at the two ends of the cable and
at the
amplifiers. Another possible variation is to use for example long Bucky Tubes
or
similar structures, in which extreme UV of even higher frequencies of light
are used,
and preferably the small holes in the Bucky (or similar) structures act as the
optical
band gap thus reflecting the light back into the tunnel.
Another mid-way variation, is to use for example fibers the size of 1-5
micron, and
then we can have many more fibers in the same space than for example 10 micron
fibers. However, for example with 1 micron we cannot use anymore the
wavelengths
around 1500 nanometers (=1.5 micron), since that would exceed the size of the
fiber, so
instead preferably the system uses for example visible light at the range of
500
nanometers and below, or even UV, and Raman amplifiers are used instead of
Erbium.
Another possible variation is to use (preferably together with DWDM), instead
of
many small fibers (or within many fibers by using for example many multi-core
holey
fibers), a large number of thin optical wave-guides within a medium that
supports them.
For example, submicron to nanometer range microstructures of wave-guides can
be
created in Lithium Niobate (LiNbO3) or other polymers, so instead of a large
number of
thin fibers, we can use a medium like this, which prevents the huge number of
signals
from mixing up by confining each channel to its own wave-guide. So this
technology,
which is currently used in optical switches, might be used also for broadband
communications. Another possible variation is using a large number of
miniature long
holograms that create a large number of small separate channels. Another
possible
variation is to use some material, preferably a flexible light-reflective
polymer or for
example holey optic fibers (for example made of glass or of plastic), so that
preferably
these fibers or flexible polymers trap light in multiple hollow cores, each
preferably
surrounded by smaller tunnels that create a light band-gap around each such
core
(which enables much better reflection), so that there is preferably one or
more cores or
even a very large number of cores, made of minute micro-tubes or nano-tubes of
air or
vacuum, so that each creates a separate channel for signals to travel through.
Preferably,
if this is done with holey fibers then there are many such fibers, each
preferably with
one or more or multiple cores, and then many fibers are preferably stacked
together for
example in multi-fiber flat jackets that move freely in the pipes, as
described
throughout this invention. Another possible variation is to preferably make
each such
fiber itself flatter so that there are for example one or a few hollow cores
height-wise
and much more hollow cores width-wise. In this case, again, many such fibers
are
preferably stacked together in multi-fiber flats jackets of any of the types
described in
this invention, or for example single flat multi-core fibers can each fill-up
an entire such
flat jacket, or a number of them fill up such a jacket. If one or more
flexible polymers
are used instead of glass, then preferably they are also wider than high, and
for example
many such flat flexible multi-hollow-core polymers can be stacked upon each
other like
the flat multi-fiber jackets, or in combination with such jackets. This has
also many
other advantages: 1. There are much less distortions or attenuations through
the air, so
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much less amplifiers and no repeaters will be needed even for longer
distances, and also
stronger lasers can be used with less problems of distortions. 2. For the
above reason,
more wavelengths can be used with closer spacing between them. 3. There is a
much
wider available range of useable frequencies (since for example this solves
the problem
of Raman scattering in optic fibers in smaller wavelengths), so a much larger
range of
wavelengths can be used. 4. For the above reasons also higher bit rates can
probably be
used, especially with the shorter wavelengths. Another possible variation is
to fill the
hollow tubes with some other gases instead of nonnal air, that are even more
optimal
for light transfer, and/or use lower air pressure or vacuum, preferably
combined with
similar lower air pressure or vacuum in the surrounding solid cable. In these
cases
where hollow cores are used, then when amplifiers are used preferably one or
more
powerful laser pumps are used to amplify the signals of many cores in free
space, for
example by shining the laser pumps over large groups of fibers at appropriate
angles (if
they are transparent fibers, such as for example holey glass fibers) or for
example in the
area of the amplifiers the signals pass through one or more preferably multi-
core glass
boxes for example with Erbium doping, preferably with the aid of delta-
connectors that
spread them on a larger area. Another possible variation is for example to
spread
Erebium particles in the air, preferably densely in a small area, or for
example in the
amplifier areas the Erbium particles are within the fibers. Another possible
variation is
for example that in the amplifier stations the fibers become non-hollow and
preferably
erbium-doped (for example by soldering together hollow and non-hollow glass
pipes
during the production process, before starting to stretch them, or, in case of
multi-hole
flexible polymers, for example by inserting non-hollow optic glass fibers in
the holes in
these areas, or by using preferably delta-like connectors, such as for example
those
described in Figs. 11a-c), and/or any of the other solutions for the
amplifiers described
in this invention are used, such as for example in those described in Figs. 4-
8.
Preferably, in the area of the amplifiers, delta-like connectors are used,
such as for
example those described in Figs. 11a-c, in order to create in that area
whatever
configuration is desired. Of course, it is also possible to use multiple
fibers, each with a
single hollow core, for these other advantages, but adding more cores to each
fiber is
also preferable. In the other direction - Another possible variation is to use
for example
multiple optic fibers each with multiple non-hollow cores, and in this case
preferably
also each fibers is wider than high. Of course these variations can be used in
combinations with other features or variations described in this invention.
These
solutions are also another way of solving the problems of friction and
possible damage
that exist when using a large number of fibers, and they also make it easier
to identify
the channels at both ends of the cable since each channel can be at an exact
position
relative to a certain fixed reference point in the polymer. These solutions
can also be
used either as in a round cable formation, or flat cable, or something in
between. Other
variations are also possible.
Another possible variation is using for example, instead or in addition, multi-
polarizations multiplexing, which means using different polarizations for the
channels
so that more channels can exist in parallel. In other words, for example, the
80 or 100
wavelengths are multiplied at least a number of times, so that within each
group all the
wavelengths have the same polarization, and between the groups a different
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polarization is used for each group. However, this solution requires
polarization-
retaining fibers, which are more expensive, and might suffer more from
dispersion
problems, so it can be used either for much smaller distances or with some
means of
correcting the dispersion. For example, if 16 or more different polarizations
are used,
preferably every once in a while appropriate consecutive polarization filters
are used
on the way, so that only light at one of the allowed polarization angles is
allowed to
pass through. This might decrease the strength of the signal, so more
amplifiers are
needed. However, due to the fact that this embodiment is more problematic, the
more
preferred embodiments are significantly increasing the number of fibers per
cable.
Brief description of the drawin2s
Fig. 1 is a schematic illustration of typical elements in a standard prior art
long-distance
submarine or overland optic fiber cable.
Fig. 2 is a schematic illustration of an example of using multi-polarization
multiplexing
in each fiber (preferably in addition to DWDM).
Fig. 3 is a schematic illustration of an example of using an extremely large
number of
optic fibers in each cable (sub-marine or overland).
Fig. 4 is an illustration of a preferable way of using many small laser pumps
for
amplifying small groups of fibers or individual fibers.
Fig. 5 is an illustration of a preferable way of using one or more one-to-many
optical
splitter in the amplifier for conveying the energy from the laser pump to the
individual
fibers.
Fig. 6 is an illustration of a preferable way of using one or more optical
splitter in the
amplifier for conveying the energy from the laser pump to individual fibers
spread
flatly side by side.
Figs. 6a and 6b are 3-dimensional illustrative drawings of two preferable ways
in
which the splitter of figure 6 interfaces with the individual fibers.
Fig. 7 is an illustration of a preferable way of using optical means in the
amplifier for
conveying the energy from one or more laser pumps to individual fibers spread
side by
side on the internal surface of the pipe.
Fig. 8 is an illustration of a preferable way of using optical means in the
amplifier for
conveying the energy from one or more laser pumps to individual fibers spread
more or
less evenly in a transparent solid or liquid in the middle of the pipe in the
area of the
amplifiers.
Figs. 9a - 9d show (through cross-sections) a few examples of some possible
structures
of a flat cable.
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Fig. 10 shows a 3-dimensional illustration of a preferable multi-fiber flat
jacket.
Figs. lOa-c show a few examples of preferable configurations of the pipes that
can be
conveniently used with multi-fiber flat jackets.
Fig. lOd shows a preferable configuration of a multi-layer, preferably
flexible, jacket
within a preferably somewhat flattened pipe.
Figs. lOe-f shows a variation where the multi-fiber flat jackets are supported
preferably
in a wavy fashion, and are preferably coupled together to each other and
preferably also
to the pipe at certain intervals.
Figures lla-b show an illustration of a few preferable types of connectors
that can be
conveniently used with the multi-fiber flat jacket, apart from the simple
connector that
is shown in Fig. 10.
Fig. llc shows an example of two such connectors in the process of being
coupled to
each other.
Fig. 12 is an illustration of a preferable example of limiting the orientation
of the flat
jackets within a set of 2 (or more) welded together round pipes.
Fig. 13 is an illustration of a preferable example of lowering the price of
DWDM lasers
and/or increasing their accuracy by optically splitting each laser to discrete
sub-
frequencies, and then modulating each of them on/off separately.
Fig. 14 is an illustration of a preferable example of optically duplicating
each original
laser beam preferably many times, and then using separate independent on/off
modulation on each of the new laser beams and sending each into another fiber
(or for
example into another core, if for example multi-core holey fibers are used).
Fig. 15 & 16 are illustrations of examples of preferable efficient optical
splitters that
use a combination of two mirrors and at least one semi-transparent mirror for
optically
duplicating each wavelength a large number of times.
Important Clarification and Glossary:
Throughout the patent when variations or various solutions are mentioned, it
is
also possible to use various combinations of these variations or of elements
in
them, and when combinations are used, it is also possible to use at least some
elements in them separately or in other combinations. These variations are
preferably in different embodiments. In other words: certain features of the
invention, which are described in the context of separate embodiments, may
also
be provided in combination in a single embodiment. Conversely, various
features
of the invention, which are described in the context of a single embodiment,
may
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also be provided separately or in any suitable sub-combination. All these
drawings
are just exemplary. They should not be interpreted as literal positioning,
shapes,
angles, or sizes of the various elements. When used throughout the text of
this
patent, including the claims, "computer" means either computer or computers.
Also, although this invention was described in various places in relation to
Erbium
or Raman amplifiers, this is just an example, and similar methods can be used
for
other types of amplifiers that may be used in the future. When used throughout
the text of this patent, including the claims, "electrical power line" means
either
line or lines. Eventhough the invetion usually refers to the cable as a metal
pipe,
this is just an example and the pipe can be made also of other materials, such
as
for example strong plastic, carbon tubes, or various alloys. Optic fibers, as
used
throughout the description, including the claims, can mean either normal optic
fibers, such as for example made of glass, plastic, ZBLAN, various saphires or
crystals, or various kinds of holey fibers, or any combinations thereof, and
can be
either multi-core or single-core fibers, including for example non-transparent
flexible polymers that contain multiple holey cores. As is clear from the
drawings, it
should be understood that throughout the specification, including the claims,
the pipe
can mean any sufficiently rigid hollow element which preferably serves as the
walls of
the optic fiber cable, even if it is not shaped like a typical pipe, so
whenever the word
pipe appears it can also mean the walls of the optic fiber cable.
Detailed description of the preferred embodiments
All of the descriptions in this and other sections are intended to be
illustrative
examples and not limiting.
Referring to Fig. 1, we show typical elements in a standard state of the art
submarine or
overland long-distance optic fiber cable. The cable (1) is typically composed
of a strong
metal shield with a typical external diameter of 2.5-5 centimeters for
submarine cables
and typically considerably less for overland cables, and contains a small
number of very
thin fiber pairs (typically around 8-12 micron each, marked 2-5), and an
electrical cable
or cables (7) for powering the amplifiers (6) along the way. The amplifier
stations (6)
are typically about 10 meters long, and at their position the pipe is
typically thicker than
normal in order to accommodate the laser pumps and their interface, and they
are
typically at a distance of about 80-120 Kilometers between each other.
Referring to Fig. 2, we show an example of using 4 different polarizations in
a single
fiber (41), as viewed in a cross-section looking straight into the fiber. Each
straight line
represents a plane in which the light waves of that polarization can travel.
As can be
easily seen, using multiple polarizations at the same time allows the beam to
take
advantage of much more space in the fiber, compared to using just one
polarization.
Each of the 4 exemplary polarized beams can contain multiple wavelengths. Of
course,
a larger number of polarizations can be used.
Referring to Fig. 3, we show a system similar to the system shown in Fig. 1,
with the
optic fibers (52) and the electrical power line (57), except that much more
fibers (52)
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are now being used in the cable (51) and the amplifiers (53) have to deal with
a much
larger number of fibers (52) simultaneously.
Referring to Fig. 4, we show an illustration of a preferable way of using many
small
laser pumps (for the sake of clarity, we show just 3 such laser pumps, marked
63-65)
for amplifying small groups of fibers (62) within the cable (61), so that each
pump for
example handles just 3 fibers preferably through appropriate splitter
interface. The laser
pumps are powered by the electrical power line (or lines) (67). These
electrical power
lines can also be actually inner isolated layers in the pipe itself. Of
course, this is just an
illustration of one example, and the number of fibers supported by each laser
pump can
change (For example 1 or more fibers per pump). Also, the cable contains of
course
much more fibers than the example shows. Eventhough the illustration does not
show it,
preferably the pipe is actually much larger at the area of the amplifier, in
order to
accommodate the laser pumps and their interfaces. Actually, since these small
laser
pumps are typically semiconductor laser diodes, they can also be used one per
each
fiber. Another possible variation is to put for example thousands of such
diodes within
one or more chips, and have a preferably very large number of fibers go
through each
chip so that preferably each fiber is interfaced with one mini laser pump.
Preferably, the
fibers are coupled to the chip by using flat mutli-fiber jackets and
connectors, as
described in Figs. lOa-b & 11a-c. It is also possible to use these small laser
pumps with
the fibers for example lying side by side (like in Fig. 6 below). Another
possible
variation is to use instead for example SOA (Semiconductor Optical
amplifiers), which
are electrically pumped instead of optically pumped, which means that making a
VLSI
multi-fibers chip is easier and energy efficiency can be higher. Preferably
this is done
without separating the wavelengths. Of course, various combinations of these
and other
variations can also be used.
Referring to Fig. 5, we show an illustration of a preferable way of using one-
to-many
optical splitters in the amplifier for conveying the energy from one or more
powerful
laser pumps (71) to the individual fibers (74) that run through the cable
(75). In each
amplifier one or more powerful laser pumps (71) is interfaced to the fibers
that it
empowers preferably by means of secondary fibers (73), each coupled at one end
to one
or more of the fibers that are (74) empowered by said laser pump and coupled
at the
other end preferably to the surface of a magnifying optical device (72) that
widens the
powerful laser beam (71) from the laser pump to the size of the surface needed
for
connecting all said secondary fibers (73) to the magnifying device surface
(72). This
magnification makes the laser light spread to a larger area, while still
maintaining its
coherent properties. Preferably, some filters are also added in order to
prevent possible
reflections and therefore some cross-talk of signal echoes between the
individual fibers
(74). Eventhough the illustration does not show it, preferably the pipe is
actually much
larger at the area of the amplifier, in order to accommodate the laser pump
(or pumps)
and its interface. If more than one powerful laser pump is used, then
preferably each
pump handles a large sub-group of the fibers. The coupling between each of the
secondary fibers (73) to its appropriate data carrying fiber (74) is
preferably done by a
wavelength-selective optical coupler or by merging with the fiber at an
appropriate
angle. Another possible variation of this is to use instead of the secondary
fibers (73),
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waveguides or holograms. Also, since one of the possible embodiments is using
a large
number of miniature waveguide instead of many fibers, they also can be
connected to
the laser beam with either secondary optic fibers (73) or secondary wave-
guides. Of
course, various additional variations or combinations can also be made. The
electrical
power lines for the laser pump (77) are for example either electrical wires,
or an inner
isolated layer or layers in the pipe itself.
Referring to Fig. 6, we show an illustration of a preferable way of using one
or more
large optical splitters in the amplifier for conveying the energy from one or
more
powerful laser pumps (81) to individual fibers (84) spread preferably flatly
side by side.
In the area of the amplifier, the cable's pipe (83) preferably extends to
contain at least
one wide flat surface (85), and the fibers (84) at the area of the amplifier
are spread on
this flat surface (85) side by side and coupled for example to a long optical
splitter (82).
There can be a number of variations in the way this splitter is made: For
example,
preferably a long semi-transparent strip of glass for example at a 45 degree
angle is
used, through which all the fibers pass, and the laser beam enters the glass
from above,
for example at a 90 degree angle to the fibers, and is projected from this
glass directly
into the length of the fibers. A large range of other angles could also be
used. Another
possible variation is that the fibers themselves in this area have a slight
curve at their
top forming the shape of the required angle. Another possible variation is
that
preferably the fibers in this section are coupled to an elongated strip of
glass that covers
them at the top, so that the top of the glass has a flat surface that faces
the laser beam,
and the bottom of the glass has a wavy surface that complements exactly the
upper
curves of the fibers, in order to make the absorption of the beam from the
laser light
more efficient. Preferably, this glass piece is separate per each fiber, so
that it's actually
more like each fiber is covered with one glass tooth with a flat top and a
concave
bottom, and the flat tops of these teeth touch each other side by side.
Preferably, in this
structure the "teeth" are glued to each other in order to make the entire
structure more
stable. However, in this variation preferably the laser beam does not hit the
glass from
straight up but at a certain angle, so that the light does not bounce back
from the fibers.
This variation is shown in more detail in Fig. 6a. These "teeth" can be made
at a large
range of heights, and in the extreme case can even touch the magnifying
optical device
through which the laser beam (81) passes, so as to conduct the beam directly
from the
laser even without any air gap on the way. Another possible variation of the
last
variation is a top glass that has the same flat surface above facing the laser
beam, but its
bottom is shaped like small upside-down triangle-shaped teeth so that each
triangle
creates a smaller beam that hits one fiber at a small point. In this
variation, preferably
the "teeth" are glued together to a covering glass plate, in order to make the
structure
more stable. This variation is shown in more detail in Fig. 6b. Another
possible
variation is that at the area of the amplifier the fibers themselves are
shaped a little
differently - for example instead of round wires they are taller and thinner
and have a
flat top. Other variations are also possible. Preferably, the laser beam (81)
from the
powerful laser pump or pumps enters the splitter (82) after passing through an
optical
device, such as for example a strip of magnifying glass, for making the
powerful beam
(81) elongated enough sideways in order to cover the entire width of the group
of fibers
(74) that are lying side by side. Preferably this magnification makes the
laser light
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spread to a larger area, while still maintaining its coherent properties.
Again, preferably,
some filters are also added in order to prevent possible reflections and
therefore some
cross-talk of signal echoes between the individual fibers (84). Eventhough the
illustration does not show it, preferably the pipe is actually much larger at
the area of
the amplifier, in order to accommodate the laser pump (or pumps) and its
interface.
Also, eventhough the illustration shows fewer fibers at the flat area compared
to the rest
of the pipe, the actual number is of course the same. In this solution, if
more than one
powerful laser pump is used, then preferably they are all illuminating
approximately the
same area, or a similar splitter is repeated a number of times at short
intervals within the
area of the amplifier and each powerful laser illuminates all the fibers at
one splitter, so
that their effect is incremental, or all the laser pumps are at the same
splitter strip, but
each laser beam is elongated enough to cover only part of the elongated
splitter so that
they work side by side. Eventhough the splitter is preferably made of glass,
it might
also be made of other materials and not necessarily glass. Other
configurations than a
flat surface are also possible, so that the fibers in the area of the
amplifier can be
arranged for example also side-by-side in a semi-circle or other shapes. Of
course,
various combinations of this and the other solutions can also be made. Of
course, this
solution is most natural in case of using multi-fiber flat jackets, for
example by
spreading them side by side at the amplification station or by using a
separate pump for
each jacket. Preferably the laser light is directed (by its positioning and/or
by additional
prisms) to enter the fibers at acceptable angles that do not cause it to
escape through the
cladding. Another possible variation is to use for example more than once such
flat
layer, for example on top of each other, with certain distances between them,
and for
example the laser sources between them. Of course at the area of amplification
the
fibers are preferably stripped off the jacket. Of course various combinations
of the
above and other variations can also be used.
Referring to Fig. 6a, we show a 3-dimensional illustrative drawing of a
preferable way
in which the small glass "teeth" (811) are coupled to the fibers (812) and
face the laser
pump beam (813) in the configuration that was described in Fig. 6.
Referring to Fig. 6b, we show a 3-dimensional illustrative drawing of another
preferable way in which the small glass "teeth" (821) are coupled to the
fibers (822)
and face the laser pump beam (823) in the configuration that was described in
Fig. 6.
Referring to Fig. 7, we show an illustration of a preferable way of using
optical means
in the amplifiers area for conveying the energy from one or more powerful
laser pumps
(93) to individual fibers (92) spread side by side on the internal surface of
the cable's
pipe (91). We show a cross-section of looking straight into the cable. In the
area of the
amplifier, the pipe (91) is preferably enlarged, and the fibers (92) are
preferably spread
side by side on the internal surface for example by either coupling them to
the internal
surface of the pipe, or coupling them to the external surface of an internal
transparent
medium (94), such as for example the same refractive glass from which the
exterior of
each fiber is made (as compared to its core). Preferably the beam from the
powerful
laser (93) comes from the center of the pipe after passing through an optical
device
(such as for example a conical prism) that makes the beam spread all around
the inner
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circle and illuminate the fibers (92) at the same time. Preferably, the fibers
are covered
with an inner transparent ring between them and the laser beam, similar to the
way that
the glass "teeth" work in solution number 8. This ring can be made at a large
range of
sizes, and in the extreme case can even touch the magnifying optical device
through
which the laser beam (93) passes, so as to conduct the beam directly from the
laser even
without any air gap on the way. Preferably this magnification makes the laser
light
spread to a larger area, while still maintaining its coherent properties.
Preferably, some
filters are also added in order to prevent possible reflections and therefore
some cross-
talk of signal echoes between the individual fibers (92). In this solution, if
more than
one powerful laser pump is used, then preferably they are all illuminating
approximately the same area, or they are positioned at short intervals with
similar
interfaces within the area of the amplifier so that their effect is
incremental, or all the
laser pumps are at the same intersection point with the fibers, but each laser
pump is
illuminating only a part of the 360 angle, so that they complement each other.
Eventhough the splitter is preferably made of glass, it might also be made of
other
materials and not necessarily glass. Of course, various combinations of this
and other
solutions can also be used. Preferably the laser light is directed (by its
positioning
and/or by additional prisms) to enter the fibers at acceptable angles that do
not cause it
to escape through the cladding.
Referring to Fig. 8, we show a schematic illustration of a preferable way of
using
optical means in the amplifier for conveying the energy from one or more laser
pumps
(103) to individual fibers (102), spread preferably more or less evenly in a
transparent
solid (104) in the middle of the pipe, preferably made of the same refractive
glass from
which the exterior of each fiber is made (as compared to its core), or for
example in a
transparent fluid (104) preferably with a specific weight close to that of
glass and a
refractive index close to that of glass, so that the fibers can freely float
there. (Another
possible variation is to add electrostatic charge to the fibers in this area
so that they
spread away from each other). This is somewhat similar to the configuration of
Fig 7,
except that the fibers (102) are not spread side by side at the inner surface
of the pipe
(10). The beam from the powerful laser (103) preferably passes through an
optical
device (such as for example a conical prism) that makes the beam spread all
around the
inner space of the cable in a small section of the area of the amplifier and
illuminate all
the fibers at the same time. Preferably, the inner surface of the pipe in the
area of the
amplifier is itself a mirror, so that it helps reflect back more light from
the laser pump
towards the fibers. Preferably, some filters are also added in order to
prevent possible
reflections and therefore some cross-talk of signal echoes between the
individual fibers
(102). In this solution, if more than one powerful laser pump is used, then
preferably
they are all illuminating approximately the same area, or they are positioned
at short
intervals within the area of the amplifier so that their effect is
incremental, or all the
laser pumps are at the same intersection point with the fibers, but each laser
pump is
illuminating only a part of the 360 angle, so that they complement each other.
Of
course, various additional variations of this can be made. Preferably, the
fibers at the
area of the amplifier are shaped a little differently, so that instead of the
round glass
cladding they have flat planes, for example hexagonal, octagonal, or other
numbers of
planes, so that the laser beam hitting them from various angles can still
enter them more
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easily. (In this case, the inner core of the fiber can either remain round or
also be made
with flat planes fitting the glass cladding, however that would be more
difficult to
accomplish). Also, if mirrors are used on the inner side of the pipe in this
area, then
preferably they are a little tilted preferably in the length direction in
order to increase
the chance of the reflection of the laser pump beam hitting the fibers at
angles other
than 90 degrees. Another possible variation, is that on each of these planes
there is also
some additional tilted glass surface, so, for example, even light coming at 90
degrees to
the fiber will still hit the plane at an angle different from 90 degrees. In
either case,
preferably, these planes are also covered with a thin layer of semi-
transparent one-
directional glass, so that it allows only the laser light to go in but no
light signals can be
reflected back out of the fibers. Preferably the laser light is directed (by
its positioning
and/or by additional prisms) to enter the fibers at acceptable angles that do
not cause it
to escape through the cladding. Of course various combinations of the above
and other
variations can also be used.
Referring to Figs. 9a-9d, we show (through cross-sections) a few examples of
some
possible preferable structures of a flat cable (110). The "walls" (111)
support the flat
structure against being squashed for example by the strong pressures in
submarine
cables, and the fibers (112) reside in the cells, in a relatively flat layout.
Many sizes of
the cells and many different quantities of fibers per cell can be used. The
fibers can be
for example in a single layer, or more than one layer at the bottom of the
cell. This way
the fibers can easily move up and down in their cells in response to different
stresses for
example when the cable is curved around the ship's wheel compared to when it's
flat at
the bottom. Of course, many variations and combinations of this principle are
possible.
At the most extreme case miniatures cells might be used so each cell contains
only one
fiber, however, such a structure might be difficult to construct and not
efficient.
Referring to Fig. 10, we show a 3-dimensional illustration of a multi-fiber,
preferably
flexible, flat jacket (1221). The jacket is preferably made of a strong, thin,
flexible, low
friction plastic or nylon or other polymer. As explained in the descriptions
of figs, lOa-
b, the jacket can either allow free movement of the fibers in their "mini-
cells" in all
directions, or only in 1 direction (preferably the direction of the thickness
of the jacket),
or almost no movement at all (in which case the jacket is preferably just a
little thicker
than the fibers themselves), and can contain either just 1 fiber per cell or
more than 1
fiber per cell. Preferably, at both ends of the long distance cable, the
jacket has modular
connectors or at least some other convenient modular pre-connector interface.
The
jacket can contain for example just one layer of fibers, or more than 1 layer.
For
example a 15 micron thick and 1.5 centimeters wide flat jacket can contain
1,000 10-
micron optical fibers.
Referring to Fig. lOa-b & l0e-f, we show a number of examples of some
preferable
configurations in which a number of flat multi-fiber, preferably flexible,
jackets (122)
can be stacked upon each other within a preferably somewhat flattened pipe
(121). This
makes sure that the pipe will only bend in the desired direction so that the
movement of
the fibers up and down within the flat jackets and/or the movement of the
jackets
themselves up and down will compensate for the stress causes by the bending of
the
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pipe. So, for example, if the size of each fiber is 10 micron and we put for
example a
spacing of 5 micron between them, we can build for example a flexible flat
plastic
jacket (122) that has a width of 1.5 centimeters and a thickness of for
example 0.1
millimeters (100 micron) and contains 1,000 fibers, or for example a similar
flat plastic
jacket that contains 2,000 fibers and has a width of 3 centimeters. In this
example each
individual fiber can preferably move freely within its 100 micron space up and
down to
compensate for stress caused by bends in the metal pipe. However, for reaching
for
example 20,000 fibers (10,000 pairs) the variation of 20 flat jackets of 1.5
cm is more
convenient than 10 flat jackets of 3 cm, because they fit better in a 2-cell
pipe, which is
structurally stronger than a 1-cell pipe. Preferably, the metal pipe in this
example is
either a partially flat pipe with an inner width of at a little more than 1.5
centimeters
and we put the exemplary 20 flat jackets in a stack on top of each other, or
the metal
pipe is even flatter and has for example two cells with a strengthening wall
between
them, and we put for example 10 jackets on top of each other in each of the
two cells.
So if for example the inner height of the cable is 0.7 cm and the thickness of
each flat
jacket is 0.1 mm, it is still 70 times larger than the flat jacket, and the
jackets can freely
move up and down to compensate for stress caused by bends in the metal pipe.
However, if the free movement of the fibers within the flat jacket is enough
for
compensating for bends in the pipe, we don't need the additional free movement
of the
jackets up and down and so can stack more such jackets together - for example
70
times more jackets and therefore 70 times more fibers. On the other hand, we
can go
also to the other direction and make the jacket extremely thin - for example
about 15
micron thick, so that the 10-micron fibers can't almost move at all, but put
more such
flat jackets in the pipe and rely more on the free movement of the jackets in
the pipe.
However, even in this version preferably there is still at least some small
gap between
the fibers and the jacket in case the therinal expansion coefficient of the
jacket is not
exactly the same as that of the glass. Also, in all the variations of the
jacket, the jacket
is preferably opaque to light and preferably black or at least with dark color
(including
between the cells), in order to further decrease the chance of cross-talk
between close
fibers. Theoretically this is even better, because at the other extreme each
fiber can
move only 0.1 mm up or down in our example in response to stress caused by
bending
of the pipe, and in this extreme for example a 100 flat jackets, with a
thickness of for
example 15 micron each, occupy together about 1.5 mm and therefore can still
move
freely up or down almost 85% of a centimeter in a pipe of 1 cm internal
height.
Therefore, another preferable variation of this is to use a multi-layer flat
jacket that has
for example a 100 layers (and is preferably thicker at the two most external
layers for
better protection) or simply, for easier construction, for example a 100 flat
jackets of
the type described above are stacked together and wrapped by some slightly
thicker
additional protective material. This is some kind of hybrid between flat
jackets and the
multi-layer structure described in Fig. 10d. However, except for increased
strength,
there is no need to actually wrap the exemplary 100 layers together, and it
might be
even more flexible if each can preferably move freely up or down exactly to
its most
convenient position with each bend. Due to the above described considerations,
this
variation of extra-thin flat jackets is very preferable. By the way, the above
calculations
show that even 100,000 and even much more 10-micron fibers can easily and
safely be
stacked together in this method without exceeding the current typical total
size of the
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pipes (except for making the pipe a little flatter and wider and preferably
with more
than 1 cell, with inner supporting walls between them). And if we go down in
another
variation for example to a size of 1 micron per fiber (and use a shorter
wavelength - For
example if the inner core of the 1-micron fiber is 0.7 micron in diameter,
then we can
use for example wavelengths starting at 400 nanometers and going downwards),
then
we can use a similar method to stack even niillions of fibers in the same size
of pipe.
However, due to cladding thickness problems, such a fiber would preferably
have for
example a core of 200 nano or less and carry for example wavelengths of 40
nano or
less. So for example, with 1-micron fibers a flat jacket of 1.5 cm width can
contain
10,000 fibers, and the jacket can be for example 10 times thinner, and we can
stack
more jackets on top of each other. However, this might make the jacket too
weak, so
another possible variation is to not reduce the thickness of the jacket below
a certain
limit. Also, reducing the fiber's thickness to less than a few microns can be
problematic
because in shorter wavelengths there are more losses, mainly due to Rayleigh
scattering, although there are optical fibers which can carry for example
signals around
850 Nanometers with losses as low as 3dB per Kilometer, and good fibers today
come
without the Hydrogen Oxide impurity that caused problems around the 1380
nanometers area. There are a few solutions to this: 1. Go down to only a few
microns,
which means that the lower loss wavelengths of about 1300-1600 can still be
used, but
still, for example, with fibers of 5 micron, 4 times more fibers can be used
in the same
space. 2, Use thinner fibers with signals for example around the 850 nanometer
area. 3.
Since the main cause of Rayleigh scattering is inhomogenities caused by
fluctuations of
glass density and compositions, producing more homogenous fibers will probably
reduce this scattering (this may be done for example by producing fibers in
space or by
planning the design of the glass density in advance to compensate for the
distortion
caused by gravity during the manufacture process). 4. It might be possible to
add some
materials to the glass that will reduce its losses at these frequencies. for
example
ZBLAN fibers, which contain Fluoride, Zirconium, Barium, Lanthanum, Aluminum
and Sodium, can work at ranges such as 1300-4000 nanometers with attenuations
as
low as 0.001 dB/Kilometer. Therefore, other variations or combinations with
glass
might help also in shorter wavelengths. 5. Use Holey fibers with smaller
tunnels, so
they can be used with shorter wavelengths wavelengths, and there is no problem
of
more attenuation or more distortions or more dispersion at the shorter
wavelengths,
since the light signals are traveling through free space. Another possible
variation is
using more than 1 fiber in each "mini-cell" of the jacket, so that for example
80 fibers
with a diameter of 1 micron can fit in the same space of 1 fiber of 10 micron,
and then
the flat jacket of 1-micron fibers will be the same thickness as the flat
jacket of 10-
micron fibers, but a 1.5 cm wide jacket will carry 80,000 fibers. Preferably,
in this case
the fibers are each covered by a very thin layer of opaque, preferably dark,
coating or
color, with preferably the same thermal expansion coefficient as glass, to
avoid cross-
talk between the fibers, or immersed in an opaque dark liquid or powder (such
as for
example fine carbon dust). Another possible variation is using the multi-layer
hybrid
variation suggested above, so that for example we stack 100 ultra-thin flat
jackets of 1-
micron fiber together on top of each other and then add a somewhat thicker
external
envelope to make it stronger, and then altogether it still has a thickness
similar to 1 flat
jacket of 10-micron fibers. By stacking for example a 100 of these exemplary
80,000
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fibers flat jackets on top of each other in the pipe, we get something the
thickness Of
about 1.5 mm that can move freely up and down in the pipe to compensate for
stress
caused by bending, and contains 8 million 1-micron fibers. Of course, the
number of
cells in the metal pipe itself can be 1 or 2 or more, so various combinations
of flat
jackets and a flat metal pipe can also be made. Of course, the numbers here
are just an
example and various other numbers and sizes can be used. For simplicity, Figs.
lOa-b
show only a few layers of the flat jacket, but, as explained, much more layers
can be
actually used. To look even at the lower bounds, for example even if the
fibers have for
example a 100 micron diameter (including cladding and coating, for example a
40
micron fiber with a coating thickness of 30 micron on each side), then for
example in
one of the configurations of Fig. 10a, for example with a typical submarine
cable of a
diameter of around 5 cm, for example each flat jacket of for example 3 cm
width can
contain for example 300 fibers and can have for example a thickness of even
150
micron (assuming for example a generous thickness of additional 25 microns for
the
thickness of the jacket's coating, and the coating can be for example a strong
polymer -
and this is for example compared to a typical thickness of 100 microns for a
typical
strip of paper, and of course it can be even much less, especially for example
if the
fibers are coated together in the jacket instead of being coated each
individually before
being coated together by the jacket, so that for example the whole thickness
of the
jacket could be for example 80-100 micron, thus providing a 20-30 micron
thickness on
each side to the for example 40 micron fibers, and if for example the coating
of the
jacket between each two fibers is around 10 micron, then the 3 cm jacket can
carry for
example 600 such fibers), then all that is needed to reach for example 10,000
fibers is
for example 17-33 such flat jackets, and even at a thickness of for example
150 micron
per jacket, the entire stack of 33 jacket would have together a thickness of
only 5 mm,
and of course with a smaller thickness, for example just 100 micron, the 33
stack would
have together a thickness of about 3.3 mm, and the 17 stack would have a
thickness of
about 1.7 mm. Another possible variation is that for example between each two
fibers
in the flat jacket (or for example between every group of fibers) one or more
additional
strength member is added (such as for example a metal wire preferably with a
diameter
similar to that of the fibers), however if such strength fibers are added they
are
preferably made of a material with a similar thermal expansion coefficient to
that of the
fibers. Of course various combinations of the above and other variations can
also be
used.
As explained above, the flat jackets are preferably loose enough to be able to
move
and bend freely. Preferably they slightly bend for example with a wavy shape
of curves,
as shown in Figs. 10e & lOf. Another possible variation, shown in Figs. l0e-
lOf (which
show a side view of the group of flat jackets), is that for example the
jackets are
stitched together and/or for example glued and/or otherwise coupled to each
other in a
way that preferably does not apply pressure to the optic fibers, preferably at
certain
intervals (for example every few dozen centimeters or more or for example
every meter
or more or every few meters or more or any other convenient interval), for
example by
wires or staples that go through the jackets at the stitch area (242), for
example at the
edges of the flat jackets where there are preferably no fibers and/or for
example in one
or more strip without fibers that runs for example lengthwise in the middle of
the
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jackets (i.e. preferably through one or more holes), so that preferably the
jackets won't
slide against each other. Another possible variation is that for example these
stitch
points or some of them or for example other points of the grouped jackets (or
of
individual jackets independently) for example connect also with the pipe
itself at certain
intervals (243) (which means that this can be for example the internal wall of
the outer
pipe, or an elongated cell in which the fibers are, as explained elsewhere in
his
application, in case the cable contains more than one compartment lengthwise
side by
side, or for example the internal wall of some inner pipe or tube, or other
enclosure
which contains the fiber jackets)(Eventhough figs 10e & lOf for clarity show
the
connection or coupling area as having some height, this is just for
illustration and of
course at the connection or coupling area the jackets can also for example
touch for
example the cable or pipe very closely, however unless the inner wall to which
the
jackets are coupled is rectangular or at least flat at the side to which the
fibers are
coupled, there is preferably at least an internal preferably flat protrusion
to which the
jackets are coupled, at least at the intervals of the coupling, for example
like an internal
fence or hedge or ramp). Preferably this coupling to the cable switches its
direction
each time, so that for example the even connections are to the bottom of the
pipe and
the odd connections are to the top or vice versa (Of course the top and bottom
can
become for example right and left if the cable is rotated, but logically it is
the same), or
at least once in a while. This has the advantage that the jackets don't slide
lengthwise
compared to the pipe for example when the pipe bends or becomes straight
again, thus
avoiding unnecessary friction, and avoiding for example fluctuations so that
at certain
areas there could be too much or too little length or slack of jackets at the
area of the
bend. Preferably each such "stitch" area is also coupled to the cable,
preferably to the
internal wall of the pipe or cable, and these stitches are preferably for
example every
meter or more or a few meters or more or other convenient interval (this means
that
preferably the intervals of coupling jackets to each other and/or of coupling
them to the
cable's or pipe's walls preferably are for example more or less constant or
for example
preferably in another variation they can change for example according to
various
considerations for example at different sections or in different patterns, so
that for
example they are sometimes smaller or sometimes larger or for example the
intervals
change in some pattern, or for example they are irregular). This coupling is
preferably
by connecting the "stitched" area for example by wires for example to some
internal
(preferably low and wide) protrusion on the pipe's inner wall, wherein said
internal
protrusion preferably has for example one or more holes in it for making the
connection, and/or for example by gluing, and/or for example by any other
known
means of preferably easy clipping or screwing or hooking or coupling in a way
that
preferably connects to the side or sides of the jackets preferably without
creating
pressure on the jacket. Another possible variation is to use for example some
flexible
stitch or hook such as for example rubber or spring or for example somewhat
loose wire
(which preferably still goes through the jackets as explained above), which
can for
example allow some bouncing that can for example change the distance between
the
jackets and the inner wall to which they are coupled, but that is less
preferable. A
further advantage of this arrangement is that the coupling of the flat jackets
to the cable
at these intervals helps ensure that the flat jackets will not rotate out of
orientation or
move too much sideways in the cable (especially for example if it is with glue
and/or
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for example staples or wires that go for example through both edges of the
jackets, as
explained above), and thus an additional advantage is that there can be larger
flexibility
in choosing the dimensions of the cell or cells in which the flat jackets move
(of course
this means that in the case of flat jackets if the coupling is for example to
an inner pipe,
preferably the inner pipe is also prevented from rotating relative to the
external pipe,
and as explained in other places in this application, in case of flat jackets
preferably the
cable can only or mainly bend in a limited direction or directions -
corresponding with
the orientation of the flat jackets). A single cell or for example two cells
is more
efficient than multiple cells, since less parts are needed and the space can
be used most
efficiently. This arrangement is much more efficient than for example the
arrangement
of Katurashima (US 5,233,678) and similar arrangements which use multiple
inner
tubes twisted around a central strength member with a structure of optic
fibers in each
tube, because in the present arrangement much less elements are needed, the
space can
be used much more efficiently, and access to the fibers is much more easy (for
example
for maintenance or for identifying individual fibers). Another possible
variation is to
use instead for example some elongated rectangular clips for the stitch, but
this is not
recommended for optic fibers since the pressure could damage the fibers.
Another
possible variation is to use a similar stitching arrangement (or other form of
coupling at
intervals) for example in the variations of using for example one or more or a
few or
more or a few dozen or more (or any other convenient number) freely moving
groups or
bundles of preferably densely packed fibers, which is similar to the way that
some
copper wires are connected every once in a while to the cable in some phone
cables
with a ring that presses the wires, however a ring which presses copper wires
is
preferably not used to press optic fibers since optic fibers are much more
sensitive to
pressure, so preferably the stitch or other coupling is preferably done by
wires or screws
that go through one or more holes in the group jackets and/or for example by
gluing the
groups to each other and/or gluing preferably that area also to the pipe.
Another
possible variation is for example coupling individual groups separately to the
cable or
for example together with some of the others (for example if there are 50
groups or
bundles altogether, then for example each 10, or any other convenient number,
are
coupled together). (In this variation all sets can be for example coupled to
the cable in
the same directions and/or for example also changing directions together, or
for
example each set is coupled in a different direction, so that they less
interact with each
other). This is more problematic and less organized and less efficient than
the flat
jackets solution, but it has the advantage that in these variations the cable
can be
allowed to bend freely in any direction. Another possible variation is to use
the same
principles of stitching or coupling at intervals for example with one or more
multilayer
structure of fibers (which can move for example freely or for example both the
structures and the pipe can bend only in one direction), or with any other
arrangement
of optic fibers within the cable. (In other words, as explained above, the
fiber jackets
can be for example stitched together only at the areas of the coupling for
example to an
inner wall of the cable or for example an inner tube, or for example stitched
to each
other also between the intervals of said coupling for example in one or more
other
intervals as explained above, or for example they are coupled to each other
all along the
way as a multilayer structure, so that the multilayer structure as one unit is
coupled at
intervals to the cable or inner tube). As explained above, in the above
variations
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preferably the waviness or bending of the fibers is preferably kept
sufficiently small
(preferably for example by using sufficiently large intervals between the
points of
coupling to each other and/or to the cable and/or by avoiding too much slack
between
the coupling points), so that the bending is preferably sufficiently or
considerably below
angles that could cause losses (but preferably the waviness or slack is
sufficient for
compensating for any bending which can occur in the cable or pipe for example
while
laying it or during operation), and preferably thinner fibers are used, such
as for
example of 40 microns or less including the cladding, which has many
advantages as
explained throughout the application, and also, as explained above, they have
considerably lower bending loss than for example fibers of 80 micron or of 125
micron
with the cladding. This is very different from prior art configurations also
because, as
explained above, according to the present invention preferably between said
intervals
the optic fibers can move more freely or substantially more freely relative to
the cable
compared to the points of coupling to the cable, and they typically move in a
hollow
enclosure (i.e. filled for example with air or gas or liquid), such as for
example the inner
cavity of the cable, an elongated cell (if there is more than one such
cavity), or for
example an inner tube within the cable (which is preferably also similarly
coupled to
the cable at least in intervals), and as is clear from the above explanation
and from Figs.
10e & 10f, this is preferably clearly asymmetric, so that at the areas of
coupling to the
cable (or cell or tube or pipe or other enclosure) the jackets are typically
substantially
more far from the opposite internal wall than from the internal wall that they
are
coupled to, which is what enables the more free movement between said
intervals. In
order to feel just how elegant and efficient and parsimonic this solution is,
one can for
example take an elongated cardboard tube of for example 20 centimeters or more
in
length for example with a few centimeters diameter (for example from typical
rolls of
kitchen paper towels) and then for example cut together 7 pieces of for
example A4
paper in the elongated direction into long strips of for example 30 cm length
with for
example 2 or 2.5 cm width, which gives about 100 such strips (so that each
such strip is
more or less similar in thickness to a flat jacket that can contain for
example even 400-
2000 optic fibers or more or a similar large number, depending on the type of
fibers
used), and then insert said strips as a group in the tube and for example
staple them
together for example at least in one place to the inner wall of the tube, for
example near
one of the edges, and then play freely with bending the tube and seeing the
behavior of
the represented jackets. As such a model demonstrates, even for example a 100
such
strips or jackets (which can represent for example 40,000-200,000 optic
fibers!) occupy
together in combined thickness for example at the area of the stapling just
around 0.5
cm (5 mm), so they can still move quite freely in the tube, and for example
stapling
them at intervals for example with switching the direction of the coupling
each time
(for example every 50 cm or 1 meter or more) in a longer tube (for example
made by
connecting several such cardboard tubes longitudinally or for example by using
a
typical plastic pipe that can carry for example electric wires in buildings,
with the
desired diameter) and using longer strips preferably with sufficient but
preferably not
too much slack for the stripes between the intervals, enables them to move
easily
without stress even with considerable bending of the pipe. Clearly this will
work the
same for example with a metal optic fiber cable of for example 5 cm outer
diameter and
3 cm inner diameter, which can preferably bend only in the desired direction,
for
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example by any of the means described in this application, such as for example
using
two welded such pipes or for example using a pipe with an ellipse cross
section and/or
other form of strengthening which favor the desired bending direction. (Of
course this
can be demonstrated similarly for example with just 10 such strips, or for
example any
number of strips between 10 and 100, or even more strips). And since, as
explained
elsewhere is this application, the optic fibers themselves typically cost much
less than
the cable (for example a few cents or less or even much less per meter
compared to for
example a few dollars or even $20 per meter for the cable), and since as
explained
above in these solutions there are much less elements needed within the cable,
and since
the huge number of possible fibers that can be included can also compensate
for
example for even a large percent of faulty fibers, these solutions can enable
at almost
the same price of current typical prior art cables, to easily use for example
even 1000 or
more times more fibers than in the prior art solutions, since a typical prior
art
transatlantic optic fibers cable today usually does not carry more than for
example 200
fibers. The above solution is much better than US patent 6,687,437, in which a
wavy
form is created by simply pressing a multilayer group of jackets into the
cable, since, as
explained above, in the present application the jackets are preferably
actually fixed to
the cable at the desired intervals in a way that preferably substantially
prevents
lengthwise sliding of the jackets relative to the cable at the coupling
points, i.e.
preferably by mechanical means (for example stitching or hooking) and/or
chemical
means (for example glue can work mechanically and/or chemically) and not by
mere
pressure (of course if for example the stitching point allows for example
slight sliding
movement for example back and forth for example within a few millimeters or
for
example a few centimeters or less for example due to some flexibility of the
stitch
preferably this does not count as real sliding, but preferably the coupling
point is fixed)
and preferably enables controlling of the size of the intervals and the amount
of slack or
looseness of the jackets between them, whereas in US patent 6,687,437 there is
no such
fixing and the wavy form is created by merely pressing the jackets into the
pipe so in
US patent 6,687,437 there remain a large number of problems which the above
variations of the present application solve: The waves in the wavy form are
much more
frequent (switching direction apparently every few centimeters, according to
the
drawings), thus creating a huge waste of fibers (which can mean more losses
and/or
need for more amplifiers if these are not holey fibers, and the possibility of
losses due
to excessive bending), lack of control over the angle of banding, lack of
control over the
spread of stresses, and ability of the multilayer structure to rotate out of
orientation. Of
course various combinations of the above and other variations can also be
used.
One preferable method of manufacturing the flat multi-fiber jackets is, for
example,
putting a large number of fiber reels at a sufficiently large area, and
pulling them next
to each other side by side for example with methods similar to textile
factories, and then
running them through a machine which extrudes the jackets around them on the
fly, or
for example letting them pass through an appropriate liquid solution, etc.
Preferably, the
various reels and relay wheels are computer-controlled for exact coordination,
and also
there are tension sensors to avoid stressing fibers too much during the
process.
Preferably, if a fiber gets torn or damaged in the process, this is
automatically sensed,
and then either the fiber is marked as bad, or the process is temporarily
halted d the
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fiber is preferably fixed by welding, and then the process continues. If the
jackets are
extruded around the fibers, they can either be extruded to fit exactly around
the fibers,
or they can be extruded with the right size of holes so that the fibers can
have the
amount of free space desired. If the fibers pass through some liquid solution
for forming
the jackets then it is more natural to have no free space between the fibers
and the
jacket, however even in this method some free space might be created for
example by
first covering the fibers with some volatile material which evaporates after
the jacket
has been fornied around them, thus leaving the desired free space.
Referring to Fig. lOc, we show another variation: Making for example a flat
flexible
jacket (122c) of the entire exemplary 20,000 fibers (123c), which would have a
width
of 30 centimeters in our example, and then rolling it like a Rollada cake and
putting it
in this form in the metal pipe (121c). The diameter of such a rolled flat
jacket with a
thickness of 0.1 mm can be about 0.3 cm. This can fit easily in a metal pipe
with an
inner diameter of 1 or 1.5 cm, and still leave enough room for the rolled
jacket to also
move freely in the inner pipe space to compensate for stress caused by bending
of the
metal pipe. However, this would be problematic since in the rolled jacket, the
free
movement space of for example 100 micron for each fiber is at a different
angle
depending of its position in the rolled jacket. Therefore, preferably, in the
rolled jacket
version, the space between each two adjacent fibers in the flat jacket is
preferably larger
(than in the examples given in Figs. l0a and b) and the jacket is thinner, for
example 30
micron space between each two adjacent 10-micron fibers and a jacket thickness
of
0.03 mm (30 micron). This would make the flat jacket of 20,000 fibers with a
width of
about 800,000 micron = 80 cm. Rolled-up, the diameter of this exemplary
"rollada" will
still be about 0.3 cm. However, if sufficient movement space is given per each
fiber in
its "mini-cell" within the "rollada", there is no need for the "rollada" to be
able to move
freely in the pipe, so a larger "rollada", containing more fibers, can be
built, filling up
more of the inner space of the pipe. Another possible variation is in the
other direction -
to allow almost no free movement in the cells within the rollada, and rely
mainly on the
movement of the rollada itself in the pipe. Of course, again, this is just an
example, and
various numbers and sizes can be used. Other shapes could also be formed from
such a
flat jacket, for example a zigzag or wavy form. The advantage of the "rollada"
solution
is that it is relatively easy to manufacture and can be easily used with the
normal round
pipes. However, since this solution allows free movements in all directions,
it is less
optimized than the solutions of 12a-b and of 12d, which use directional
optimization so
that the fibers can move freely more in the direction needed to compensate for
stress
caused by bends in the pipe, and less in other directions that are not needed,
and thus
enable safely stacking much more fibers per pipe without increasing the size
of the
pipe. Smart solutions that do not require enlarging the metal pipe are
extremely
important since the pipe is the most expensive part of the cable, and since we
want to be
able to enable as much as possible long consecutive cables that can be laid in
one run.
Referring to Fig. lOd, we show a, preferably flexible, multi-layer, preferably
elongated
square, structure (122) which is already shaped in multi-layer format, without
the need
to roll it, so that each fiber still has enough room to move freely in its own
channel and
said structure is preferably within a somewhat flattened pipe (121), in order
to make
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sure that the pipe bends only in the desired direction. Preferably the fibers
(123) have
more free room to move up and down than sideways. This saves space by giving
the
fibers free movement especially in the direction that is needed to compensate
for stress
caused by bends in the pipe and less free movement in the other direction, so
that more
fibers can be safely stacked together sideways. For the simplicity of the
illustration only
a small number of "mini-cells" and fibers is shown, but of course the number
is actually
much larger. Another possible variation of this multi-layer format is having
more than 1
fiber per "mini-cell', in order to save materials and space. Stacking more
than 1 fiber
per each "mini-cell" is also possible with the other configurations described
in Figs.
lOa-c.
Referring to Fig lla-b, we show a multi-fiber flat-jacket connector (132) that
is shaped
like a fan or delta, so that the distances between the fibers (131) increase
near the
connector in order to allow more convenient access to the fibers, for example
when
connecting them to the laser interface that sends the wavelength signals into
the fibers
or for making stitches between fibers. Preferably, the distances between the
fibers at the
end of the connector (133) and the orientation (preferably, all pointing at
exactly the
same direction in parallel) of the fibers (133) are kept extremely accurate,
for example
by using very accurate filaments between the fibers at the connector (132),
which are all
of the same size, preferably to a micron-level accuracy or even higher.
Preferably, the
material of the connector and of these filaments and the material of the flat
jacket itself
have a very similar thermal expansion coefficient. In Fig. 11a the fibers
remain with the
same thickness in this "delta". Fig. 11b is very similar to Fig. 1 la, except
that the fibers
are also getting gradually thicker at the delta as they approach the
connector. So, for
example, if at the last meter or less or few meters of the connector the
fibers for
example gradually each grow to a thickness of for example 10 times their
normal
thickness, then for example a flat jacket of 1000 fibers with a normal width
of about 1.5
cm will have a connector with the size of approximately 15 cm. For convenient
access,
preferably the deltas of both Figs. lla and 11b can grow to any desired size,
for
example even 1.5 meters, and in the version of Fig 11b the growth of the final
connector does not have to grow at the same ratio as the growth in the
thickness of the
fibers, so that, for example, the thickness of each fiber can grow by a factor
of 10 and
the distances between them can grow even further, so the final size of the
connector can
still become for example 1.5 meters, even if each fiber grew for example only
10 times
in thickness. In either case, the fibers' edges at the end of the connector
are preferably
already cut very straight and well-polished. Such connectors can help for
example at the
connection with the lasers that insert the input signals into the fibers, at
the connection
with the signals detectors, at the area of the amplifiers, in small-distance
point-to-point
connections, and/or in various junctions or optical splitters at the routers.
For
connection with the laser diodes such an expanded connector is convenient
because the
laser diodes are typically each larger than the fiber. The variation described
in Fig. l lb
is especially important if we move for example to thinner fibers, such as for
example 5
micron instead of 10 micron.
Referring to Fig, 11c, we show a top view illustration of two connectors (132)
in the
process of being coupled to each other with the aid of a coupling interface
(134). When
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the connection is being made with other fibers, it can either be mechanical,
so that two
connectors can be mechanically coupled to each other in a way that each fiber
is
touching and mechanically well coupled to the appropriate fiber as optimally
as
possible, or (since fused fibers work typically better than a mechanical
interface) the
connectors can be used for example as a jig to help a fusing machine
automatically
weld each two fibers together. If the connection is mechanical, the coupling
interface
(134) can be for example a very exact array of short glass hollow tubes
embedded in
parallel in a rigid connector of the same material and size as the connectors
(132), so
that the connectors (132) are exactly coupled mechanically to the interface
connector
(134) and each hollow glass tube fits exactly over two facing fibers between
the two
connectors (132). Another possible variation is that in one of the two
connectors (132)
the fibers get thicker as in Fig. 11b and become hollow at the end, and the
fibers at the
other connector fit exactly into each hole of the corresponding fiber when the
two
connectors are coupled to each other. In this case, preferably the thin wires
on the other
connectors are also getting somewhat fatter, so that the cores on both
connectors are
similar or identical in size and only the glass claddings on one side are
larger then the
other and form the walls of the holes. This way the communication direction is
independent of the connector type. Otherwise, this kind of connection would be
limited
to sending signals from the thin side to the fat side, otherwise data could be
lost.
Another preferable variation is that for example when the two connectors (132)
are
coupled together, two or more opposite-facing very exact wavy-like clamps are
mechanically closed on the fibers from the top and from the bottom and hold
all pairs of
"stitched" fibers together. A further variation is that preferably some part
of these
clamps can be slightly moved for example to the right and others slightly
moved for
example to the left, so that the fibers are held in position with the addition
of some
force from the right and from the left. Various combinations of these and
other
variations are also possible.
If the connectors are used as a jig for welding the fibers together, then
preferably the
two connectors (132) are mechanically coupled together from the sides, leaving
free
access from above and/or from below to the bare fibers between them, so that
each two
matching fibers are in very close contact, and then an automatic welding
machine
sensor can for example reach the connecting point of the two fibers from below
or from
above, encircle the matching fibers at the connection point (for example by
closing a
clamp made of two or more half-rings), make automatic adjustments to make the
connection optimal, and then weld the two glass fibers with the appropriate
heat
required. This is done either serially per each pair of matching fibers, or in
groups, so
that for example each set of 10 or 100 fibers are welded in parallel at the
same time, or
even the entire set of fibers in the flat cable are welded this way in
parallel at the same
time. After the welding is finished, preferably the area of the bare fibers is
covered from
above and from below for protection. If two coupled connectors of welded
fibers need
to be separated, then preferably a similar reverse process is used, so that
again the
welded fibers are exposed from the top and/or from the bottom, and for example
a
similar machine cuts each pair of matching fibers at the connection point and
automatically polishes each of the two cut fibers to have a very exact end at
90 degrees
to the length of the fiber. This welding can be done also in the variations
where in one
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or both of the connectors the fibers are getting fatter at the connector.
These connectors
(in either the mechanical connection or the welded connection) are also
another solution
to the problem of stitching at sea for especially long submarine cables and
for easier
interface with the amplifiers. Preferably, such stitching is done near or
inside one of the
amplifiers, to compensate for any attenuation caused by the stitches.
Preferably the
gradual thickening of the fibers at the edges is created for example by vapor
deposition,
for example by drawing the fibers slower when the edges are being covered. In
the
variations where the core itself also becomes thicker at the edges, this can
be done for
example by gradual different drawing for the fibers at their ends, so that
they remain
thicker gradually and/or for example by vapor deposition of the same material
of the
core near the edges, but the variations where the core remains the same and
just the
cladding gets thicker gradually are more preferable. Another possible
variation is that
preferably the connector at the end of the individual fiber or for example the
other
connector that has to connect with the connector end in which the fiber
terminates,
preferably one of them preferably has a shape like a widening hollow cone and
preferably this cone can flexibly bend in any needed direction (preferably in
a limited
range of angles so that it does not bend out of orientation), so that, even if
the fibers are
not exactly aligned, the connector that goes into the hollow cone is
preferably
automatically guided into position. Another possible variation is for example
that the
widening hollow cone does not bend flexibly and instead the connector end that
enters
into it is mounted in a flexible way so that the hollow cone guides it into
position.
Another possible variation is that for example both the hollow cone and the
other
connector end that goes into it can preferably bend flexibly in a preferably
limited range
of angles in order to automatically reach the desired fit. Another possible
variation is
that at least one of the cone and the connector that goes into it can also
preferably move
automatically for example in a limited range of movement, in order to find
automatically the correct position. Preferably the inner (narrower) end of the
hollow
cone has a sufficiently small diameter to make the other connector reach
exactly the
desired position and stay there as the connectors are inserted into each
other. Another
possible variation is that for example instead of or in addition to this
arrangement at the
end of individual fibers, a similar flexible arrangement for automatically
sliding into the
correct position is used for example in groups of fibers, so that for example
every 10 or
20 or 100 fiber edges (or any other convenient number of fibers) are mounted
together
on a unit that has this flexibility for the group being connected.
Referring to fig. 12, we show a preferable example of limiting the orientation
of the flat
jackets within a set of 2 (or more) round pipes (141). In the shown cross
section of the
pipes, the flat jackets (142) in each pipe are preferably in an elongated
square cell
which has a height smaller than the width of the jackets. The empty spaces
created at
the top and at the bottom are preferably used for electrical wires (144 a-d)
for the
amplifiers. Additional smaller electrical wires can be used for example in the
side
spaces. This can also be combined with other solutions, so that for example
these wires
can be in addition to inner insulated layers of the pipe itself that are used
as electrical
wires. Of course, in these solutions the pipes are preferably smaller, so that
altogether
the complex of pipes is not larger than a single pipe of the type used today.
Also, more
than one cell per pipe can be used sideways and/or bottom-up (For example,
even
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simply dividing each of the two pipes into two cells, one on top of the other,
can solve
the jacket orientation problem), but one cell per pipe is more efficient.
Also, preferably
the cells have walls that are straight and parallel to each other, since
otherwise one or
more flat jackets can get stuck while at one of the extremes and not get down
again
when needed. Preferably, the cell walls are also made of strong metal.
Referring to Fig. 13, we show a preferable example of lowering the price of
DWDM
lasers and/or increasing their accuracy. The light (152) from laser source
(151) is
optically split for example by an optically diffractive prism (for example in
the shape of
a triangle or convex lens or round edges) (153), preferably with alternating
opaque and
transparent stripes, into discrete sub-frequencies (154a-e), and then
preferably each sub-
frequency is amplified and modulated on/off separately for example by using an
electro-absorptive modulator or Mach-Zehnder Modulator or a lithium niobate
modulator (155a-e). This can convert each single less precise laser to a group
of more
precise lasers. In other words each laser can be used for creating a number of
wavelengths. The new modulated wavelengths (158a-e) then enter a multiplexor
(156)
and are inserted into the optic fiber (157). So for example, instead of 120
separate laser
sources for 120 wavelengths, for example only 12 lasers can be used, each
split for
example into 10 wavelengths. For increased efficiency, preferably the
amplification and
the on/off modulation are conducted simultaneously at the same place, for
example by
using a filter and on/off-modulating the amplification pump itself. Another
possible
variation is to use the amplification on the entire set of wavelengths
together before or
after they enter the fiber. Preferably, at this point the separate beams also
pass through a
correcting lens that compensates for any smearing caused by the first prism.
Preferably
this is used in combination with various filters for improving the purity of
each
wavelength. Another possible variation is for example to optically duplicate
the original
laser and then use a separate filter or set of filters for each wavelength. An
even better
solution is to optically duplicate each original laser beam preferably many
times, and
then use preferably amplification and separate independent on/off modulation
on each
of the new laser beams and send each into another fiber, as shown in Fig. 14.
This way
for example each original more expensive and precise laser can be used
simultaneously
to independently send separate signals into a preferably large number of
fibers.
Preferably the splitting is done after the filters that further purify the
beam, so this saves
also on the typically expensive filters. Preferably all of these units are
combined on a
single chip or for example a number of chips, with preferably many lasers and
many
fibers per chip.
Referring to Fig. 14, we show an illustration of a preferable example of
optically
duplicating each original laser beam preferably many times, and then using
separate
independent on/off modulation on each of the new laser beams and sending each
into
another fiber. For simplicity and clarity, in this example there are shown
only 3
wavelengths and 3 fibers, although preferably there are many more wavelengths
and
many more fibers, such as for example 80-160 wavelengths and for example 100-
10,000 or more fibers. The original exemplary 3 wavelengths (162, 172 and 182)
originate from 3 preferably high precision laser sources (161, 171, and 181,
respectively), preferably each said source containing its set of filters that
further purify
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the beam. Each of these beams is then preferably optically duplicated by
duplicators
163, 173 and 183 respectively, into beams 162a-c, 172a-c, and 182 a-c. Each of
the
resulting new beams is then preferably separately and independently on/off-
modulated
by modulators 165a-c,175a-c, 185a-c (which can be for example electro-
absorptive
modulators or Mach-Zehnder Modulators or lithium niobate modulators),
respectively,
and then enters the appropriate input line in multiplexors 166, 176, and 186,
connected
to optical fibers 167, 177 and 187, respectively. Another possible variation
is to use the
same optical duplicating device for more than one wavelength. Preferably, in
each fiber
the set of wavelengths in that fiber are then optically amplified, for example
by Erbium
or Raman amplifiers, to compensate for the reduction in light amplitude after
the optical
duplication and splitting. So if there are for example 100-1000 fibers and for
example
160 wavelengths, this configuration can save a lot of money by using for
example only
160 high precision lasers and preferably only for example 160 sets of filters,
since each
laser typically comes with its typically expensive filter and some of them
need also
temperature stabilization devices, etc. In this example we also save on
amplifiers since
we use them only after the wavelengths of each fiber have been entered
together, so the
only component that needs to be duplicated by the number of wavelengths times
the
number of fibers is the on/off modulators. Another possible variation is for
example to
amplify the beams during the duplication, for example by using erbium-doped
elements
in the duplicators optical elements themselves (for example in the mirrors
and/or semi-
transparent mirrors described in the reference to Figs. 15 & 16). Preferably
the number
of duplicates of each original beam is not too large so that it doesn't weaken
the signal
too much. In the other direction - another possible variation is to amplify
together the
signals for more than one fiber, for example with any of the methods described
in Figs.
4-8. Another possible variation of this is to amplify preferably large groups
of the
beams together for example after the duplicated beams emerge from the
duplicators and
before they enter the fibers, for example by shining a preferably powerful
laser pump
(or pumps) on them while they pass through an erbium-doped glass box or for
example
doing it directly in free space for example by spreading a lot of Erbium
particles in the
air. This can save a lot of connectors and overheads. Preferably all of these
units are
combined on a chip, with preferably many lasers and many fibers per chip. On
the other
hand, due to yield problems in producing the DWDM lasers, another variation is
for
example to create the part with the high precision lasers separately and then
couple it to
a chip or chips with the other elements. Another possible variation is that
each on/off
modulator can handle simultaneously more than one laser beam, in order to save
on
modulators, for example by dividing each modulator into sub-units that can be
each
independently controlled. Since each set of lasers can be used this way for
many fibers,
another possible variation is to use for example more expensive and more
powerful
lasers. For the optical duplication, one possible variation is for example
using a round
or elongated magnifying glass for spreading each laser beam, and then
collecting parts
of the beam and preferably letting them pass through a correcting lens that
compensates
for the spreading caused by the magnifying glass. Another possible variation
is to add
for example dark miniature stripes to the magnifying glass, like in Fig. 13,
in order to
make the spreading beam already discretely divided upon exiting the glass.
Another
possible variation is to use for example a multi-faceted magnifying glass with
each
facet straight, instead of a rounded glass, so each resulting beam is not
spreading.
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Another possible variation is to use for example sets of semi-transparent
glass that
duplicate each entering beam into two or more beams and then continue with the
same
process recursively on each of the new beams until a sufficient number of
beams has
been created. Another possible variation is to use for example multi-faceted
prisms in a
similar recursive fashion. Another possible variation is to use efficient
duplicators that
do not cause spreading of the beams during the process of the duplication and
need
much less elements than in the recursive solutions, as shown in Figs. 15 & 16.
A7nother
preferable variation is to use other DOEs (Diffractive Optical Elements) for
the
duplication, preferably for example Dammann gratings (or other types of
gratings),
which produce many output beams from each input beam. Although the above has
been
described regarding on/off modulators, it might be used also with other
modulators that
may exist in the future. Of course, various combinations can also be used,
such as for
example using some of the features described in the reference to Fig. 13 in
combination
with this. Of course the duplications can be done by any means known to the
art.
Referring to Fig. 15 we show a top view illustration of an example of a
preferable
efficient optical splitter that uses a combination of at least two mirrors and
at least one
semi-transparent mirror for optically duplicating each wavelength a large
number of
times. For clarity and simplicity we show in this example only one wavelength
(110)
entering a set of for example vertically standing mirror (viewed from above).
Of course
this is just an example for convenient viewing, and the mirrors can be also at
other
angles for example in relation to earth. In this example the two most extreme
mirrors
(101 and 103) are preferably normal mirrors and the inner mirror (102) is a
preferably
semi-transparent mirror. Preferably the mirrors are not parallel but with a
preferably
slight angular spreading, so that for example as we move to the right the
distances
between the mirrors are preferably slightly increasing. Each time the light
beam reaches
the semi-transparent mirror it is split into two separate beams and the angle
of
refraction keeps changing, so that the beams preferably do not overlap. After
a number
of iterations the wavelength exits on the other side, divided into a
preferably large
number of duplicates. Of course, by changing the angle of entry the number of
resulting
duplicates can be easily controlled. At this point preferably the beams pass
through a
correcting lens (120) that makes them parallel again for more convenient
interface with
the on/off modulators (For example if many modulator are on the same chip it
is more
efficient to have them built in parallel). Another possible variation is a
multi-faceted
correcting lens, or a set of angular mirrors on the right exit points. This
correcting lens
can be for example a concave parabolic lens. When entering more wavelengths,
one
possible variation is for example using phase shifting (so that wavelength 111
enters in
parallel to wavelength 110), and as they move inside the set of mirrors they
tend to
grow closer. In this case the result is sets of wavelengths, so that each
resulting
duplicate beam has the other wavelengths near it upon exiting. Another
possible
variation is to use for example also the height of the mirrors, so that for
example if the
mirrors are each 1 cm tall, the first wavelength is reflected back and forth
at height
lmm, and the second wavelength is reflected back and forth at height 2mms,
etc. Of
course the actual sizes are much smaller since preferably these are miniature
mirrors
within a chip. This way for example if we split for example 160 wavelengths
into for
example 100 duplicates each, the output will be a matrix of light beams where
all the
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duplicates are side by side width-wise and all the wavelengths are side by
side height-
wise. Another possible variation is to send the wavelengths together into the
duplicator
and then use a demultiplexor to separate them in each duplicated beam, but
that is less
efficient. Another possible variation is to use for example 3 inner semi-
transparent
mirrors instead of 1, which makes the splitting faster so the length of the
mirrors can be
smaller. Another preferable variation is that, instead of angular deviation,
all the mirrors
are parallel, and the semi-transparent mirror in the middle is closer to one
of the
external mirror more than the other, as shown in Fig. 16. Preferably all of
these
components are combined on a chip, with preferably many lasers and many fibers
per
chip. Preferably the mirrors and semitransparent mirrors are very accurate in
order to
prevent distortions in the signals. Of course various combinations of the
above and
other variations can also be used.
Referring to Fig. 16 we show a top view illustration of an example of a
preferable
efficient optical splitter that uses a combination of at least two mirrors and
at least one
semi-transparent niirror for optically duplicating each wavelength a large
number of
times. For clarity and simplicity we show in this example only one wavelength
(210)
entering a set of for example vertically standing mirror (viewed from above).
Of course
this is just an example for convenient viewing, and the mirrors can be also at
other
angles for example in relation to earth. In this example the two most extreme
mirrors
(201 and 203) are preferably normal mirrors and the inner mirror (202) is a
preferably
semi-transparent mirror. Preferably the mirrors are parallel and the semi-
transparent
mirror in the middle is closer to one of the external mirror more than the
other. This
way all the exiting beams are parallel (in two groups) and there is no need
for a
correction to make them parallel. Another possible variation is to make one of
the two
external mirrors longer, so that both groups exit in the same direction. In
this version
making the mirrors longer beyond a certain minimum does not create more beams,
but
by making the angle of entry closer to 90 degrees much more beam/s can be
generated
(however, in this variation some beams may overlap, so they may come out
stronger
than others, but this is no problem since they all preferably reach saturation
after the
amplification). In this version, if more than one semitransparent mirror is
used then
preferably all of these mirrors are with parallel different distances from
each other.
Entering additional wavelengths is preferably done as described in the
reference to Fig.
15. Of course various combinations of the above and other variations can also
be used.
While the invention has been described with respect to a limited number of
embodiments, it will be appreciated that many variations, modifications,
expansions and other applications of the invention may be made which are
included within the scope of the present invention, as would be obvious to
those
skilled in the art.
