Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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DEVICES AND METHODS FOR SWITCHING TRANSMISSION OF LIGHT
FROM ONE FIBER TO ANOTHER
BACKGROUND OF THE INVENTION
1. Field of the invention.
The present invention is related to the field of fiber optics communications,
and
more specifically to devices and methods for switching transmission of light
from one
optical fiber to another. This application claims priority from U.S.A.
Provisional
Application No. 60/261,351 filed on January 12, 2001, which is hereby
incorporated by
reference.
2. Description of the related art.
Light signals are transmitted through optical fibers. These are very thin, and
made in very large lengths (e.g. of the order of 1 km or longer).
Often electrical signals are converted to light signals, then transmitted
through
fibers, and then reconverted to electrical signals. Fibers are thus widely use
for wired
' communications over long distances, such as for telephone lines, etc.
It is often desirable to have an optical fiber switch device. That device can
receive light from one fiber (often called the feeding fiber), and couple it
to a receiving
fiber. Or it can couple the received light selectively to one of many
receiving fibers.
This prevents the need of reconverting a light signal to an electrical signal
for switching
between channels, and then converting it back to a light signal for continuing
transmission.
Optical fiber switch devices are implemented in a number of ways in the prior
art.
A first such way is described herein as Fig. 1 and Fig. 2. It has been
reproduced from an
article titled: Mechanical Optical-Fibre Switch, Electronics Letters Vol. 12,
July 22 1976.
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Refernng to Fig. 1, prior art switch 100 is provided in a glass tube 110 that
defines ari enclosure 115. A feeding fiber 120 enters enclosure 115, and
couples light
into either one of receiving fiber 132 or receiving fiber 134. Enclosure 115
may be
sealed, and filled with propyl alcohol to keep the ends of fibers 120, 132,
134 clean.
Referring to Fig. 2, a cross section of tube 110 is shown, at a plane where
receiving fibers 132, 134 have their inputs. Tube 110 internally has a square
cross
section, and receiving fibers 132, 134 are at corners of the square, in
corresponding
grooves. Feeding fiber 120 can be more reliably aligned with either one of
receiving
fibers 132, 134, by being driven to the same groove.
Returning to Fig. 1, feeding fiber 120 has a ferromagnetic sleeve 140, made
from
nickel. This way the output end of fiber 110 can be driven to either groove by
applying
magnetic forces. These may be established by electromagnets (not shown).
Other implementations (not shown separately) use a reed switch to switch the
device on and off, by deflecting or not the output end of the feeding fiber
from an aligned
position. A conventional reed runs along the entire length of the portion of
the feeding
fiber that is within tube 110 of the prior art. The magnetic field runs
parallel to the
conventional reeds, and in fact, it magnetizes them.
A consistent problem in the prior art is that large magnetic fields are needed
to
accomplish switching in devices such as that of Fig. 1. That is, because the
electromagnets for establishing the field are best placed outside the portion
encapsulated
by the glass tube, and therefore at a large distance from the fiber that is to
be steered by
applying the magnetic field. Due to the large distance, these electromagnets
require a lot
of electrical current to activate, more than is justified for a mere switch.
The problem has not been addressed satisfactorily in the prior art.
First, in the prior art of Fig. 1 the problem does not seem addressed at all.
In fact, .
the disclosure of the reference does not seem fully implemented. The reference
even
concludes with a statement that the authors intend to proceed with development
along the
lines indicated in the disclosure. The reference seems to treat the actual
process of
switching as an abstraction, without addressing the large size of the
requisite magnetic
fields. In fact, sleeve 140 seems shorter than subsequent, actual
implementations.
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Second, in the aforementioned implementations of reed switches, a large reed
is
used, which is at~least as long as the whole output end of the output fiber.
This was done
for better magnetic coupling. Still, such switches require a lot of current.
Third, referring to Fig. 3, another device in the prior art actually solves
this
problem, but by increasing mechanical complexity and thus also cost. The
solution of
Fig. 3 of the present document is taught in U.S. Patent No. 4,415,229.
In Fig. 3, a device 300 receives a feeding fiber 317 (near the top) goes
through a
guiding sphere 320. Sphere 320 can be rotated to various orientations, for
aligning the
free end of feeding fiber 317 with the receiving end of any one of receiving
fibers 310.
Sphere 320 is steered to these various orientations by electromagnets 326
attracting
selectively a disc 319 fitted about sphere 320.
All this is done so that magnetic fields need not be applied over large
distances.
Indeed, sphere 320 is placed in a socket, and helps form an enclosure 330 that
contains
the free ends of feeding fiber 317 and receiving fibers 310. This way disc 319
is wholly
outside enclosure 330, which permits it to be located closely to
electromagnets 326.
The drawback here is a very complex structure with mechanical parts moving
against each other. This makes it expensive, and of a shorter useful life.
It is desirable to have an inexpensive, durable fiber-to-fiber switch.
BRIEF SUMMARY OF THE INVENTION
The present invention overcomes these problems and limitations of the prior
art.
Generally, the present invention provides devices and methods for switching
transmission of light from one fiber to another. A steerable fiber terminates
in a capsule,
as do one or more cooperating fibers. For switching, the steerable fiber is
moved to
exchange light selectively with one of the cooperating fibers.
The end of the steerable fiber includes an armature that moves in response to
applied magnetic fields. At least one magnetic field is generated, and a pair
of pole
pieces transfers it to a location inside the capsule that is close to the
armature.
The invention offers the advantage that the generated magnetic field need not
be
large, thus conserving electric current. Indeed, the pole pieces terminate in
a short
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distance between them, to generate relatively large field strength. A switch
is thus
created that is economical to operate.
In addition, by further terminating close to the armature, the strength of the
generated magnetic field need not be large in the first place. Furthermore,
the armature
itself need not be large, and maybe manufactured economically near the end of
the
steerable fiber as a sphere. A switch is thus simple, and further economical
to
manufacture.
The invention will become more readily apparent from the following Detailed
Description, which proceeds with reference to the drawings, in which:
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a diagram of a fiber-to-fiber switching device in the prior art.
Fig. 2 is a cross sectional diagram of a tube of the device of Fig. 1.
Fig. 3 is a diagram of another fiber-to-fiber switching device in the prior
art.
Fig. 4A is a perspective view of a fiber-to-fiber switching device made
according
to an embodiment of the present invention.
Fig. 4B is a top view of salient parts of the device of Fig. 4A, showing one
of its
attainable switching states.
Fig. 4C is a top view of salient parts of the device of Fig. 4A, showing
another
one of its attainable switching states.
Fig. 5A is a perspective view of a~fiber-to-fiber switching device made
according
to another embodiment of the present invention.
Fig. 5B is a top view of salient parts of the device of Fig. 5A, showing one
of its
attainable switching states.
Fig. SC is a top view of salient parts of the device of Fig. 5A, showing
another
one of its attainable switching states.
Fig. 6A is a perspective view of a fiber-to-fiber switching device made
according
to yet another embodiment of the present invention.
Fig. 6B is a top view of salient parts of the device of Fig. 6A, showing it at
a rest
state.
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Fig. 6C is a top view of salient parts of the device of Fig. 6A, showing it at
a first
one of its attainable switching states.
Fig. 6D is a top view of salient parts of the device of Fig. 6A, showing it at
a
second one of its attainable switching states.
5 Fig. 7 is a flowchart illustrating a method according to an embodiment of
the
present invention.
Fig. 8 is a plan view of parts of a switch, for describing technical
implementation
details of the invention.
Fig. 9 is a detailed view of a steerable optical fiber in the device of Fig.
8.
Fig. 10 is a schematic view of an arrangement of pole pieces operating to move
a
single steerable fiber along different directions for placing in horizontally
disposed
grooves.
Fig. 11 is a plan view of an arrangement where feeding fibers share a common
armature according to an embodiment of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS)
As has been mentioned, the present invention provides devices and methods for
switching transmission of light from one fiber to another. A steerable fiber
terminates in
a capsule, as do one or more cooperating fibers. For switching, the steerable
fiber is
moved to exchange light selectively with one of the cooperating fibers. The
invention is
now described in more detail.
Referring now to Fig. 4A, a fiber-to-fiber switch 400 is shown. Switch 400
includes a capsule made from a bottom half 404 and a top half 406. In Fig. 4A,
top half
406 is shown separated and raised from bottom half 404 to better illustrate
other
important components of switch 400.
Top half 406 normally closes down on bottom half 404, to make the switch
rugged. When the two halves are closed, an interior 408 of the capsule may
optionally be
filled with an index matching fluid, to improve coupling of light between the
fibers.
Switch 400 also includes a first electromagnet 410 for selectively generating
a
first magnetic field. First electromagnet 410 includes at least a coil 412 and
a wire 414
wrapped around coil 412.
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First electromagnet 410 is operated by electrical power source such as battery
416, and a switch 418 for controlling when electrical current flows around
coil 412.
Switch 418 may be electronic, and be switched ON and OFF by an electronic
switching
signal.
First electromagnet 410 is outside the capsule, although that is not
necessary.
First electromagnet 410 may equivalently be implemented within the capsule.
Switch 400 moreover includes a first pair of pole pieces 420. Pole pieces 420
transfer the first generated magnetic field from the tips of coil 412 to a
first transferred
field location 424 inside the capsule near the tips of pole pieces 420. Pole
pieces 420 are
preferably made from a material that conducts well a magnetic field.
At least the tips of pole pieces 420 are in part inside the capsule. If first
electromagnet 410 is wholly within the capsule, then pole pieces 420 may also
be wholly
within the capsule.
In the preferred embodiment, coil 412 of first electromagnet 410 is outside
the
1 S capsule. Pole pieces 420 then transfer the first generated magnetic field
through a wall of
the capsule.
Pole pieces 420 are preferably thin, so as to interfere only minimally with a
lip of
top half 406, as it closes with bottom half 404 to form the capsule. The two
halves may
be sealed together using a foamy material between them, which accommodates a
small
thickness of pole pieces 420. Alternately, one of the two halves (here top
half 406) may
have recesses 421 at the lip, for accommodating pole pieces 420.
Switch 400 additionally includes a steerable fiber 430, having an end 432 in
the
capsule. End 432 is also known as the output end of steerable fiber 430.
A large portion of steerable fiber 430 is outside the capsule, including a
remote
end of fiber 430. This large portion, along with the remote end are not shown,
as
unimportant to switch 400. End 432 in the capsule is steerable, as will be
explained
below.
Fiber 430 is generally mounted on the bottom half 404 of the capsule. Mounting
may be to a pedestal, which may in turn be mounted on the bottom half 404.
Alternately,
mounting may be to a wall or lip of bottom half 404.
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Switch 400 further includes an armature 435 attached to steerable fiber 430
near
end 432. Armature 435 may be a standalone magnet, by being made from material
which
is inherently magnetized, or has been made to acquire magnetism. Alternately,
armature
435 may be made from soft magnetic material, which responds to magnetic field,
but
does not retain magnetism.
It is highly preferred that the first transferred field location 424 is
designed to be
close to armature 435. This way armature 435 is responsive to the transferred
first
magnetic field by being magnetically biased with respect to the first
transferred field
location 424. If armature 435 has no magnetism, then being magnetically biased
means
being attracted towards the first transferred field location 424. On the other
hand, if
armature 435 has magnetism, then being magnetically biased means being
attracted
towards or repelled from the first transferred field location 424, depending
on the
orientation of its North-South field, and the orientation of the transferred
magnetic field.
Switch 400 further includes at least one cooperating fiber 440, having an end
442
in the capsule. In addition, switch 400 further includes a second cooperating
fiber 450,
having an end 452 in the capsule. Including second cooperating fiber 450 is
highly
preferred, but not necessary for practicing the invention.
Light may be exchanged between steerable fiber 430 and either one of
cooperating fibers 440, 450. If steerable fiber 430 is the feeding fiber, i.e.
the fiber that
brings the light in switch 400, then switch 400 is a 1 x2 switch. If
cooperating fibers 440,
450 are the feeding fibers, then switch 400 is a 2x1 switch. Not including
second
cooperating fiber 450 would simply render device 400 an ON/OFF switch between
fibers
430, 440.
Referring now also to Fig. 4B, and Fig. 4C, the operation of switch 400 is
described.
In Fig. 4A, Fig. 4B, switch 418 is open, and the first magnetic field is not
generated. Accordingly, armature 435 is not biased, and end 432 of steerable
fiber 430 is
at a rest position.
In Fig. 4C, switch 418 is closed, and the first magnetic field is generated.
Accordingly, armature 435 is biased, and end 432 of steerable fiber 430 is
moved from
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the rest position to a first position, where end 432 is aligned with end 442.
There it can
exchange light substantially efficiently with end 442 of first cooperating
fiber 440.
In the drawings, it the biased armature 435 is shown contacting pole pieces
420,
although that is not necessary for practicing the invention. Alternate
arrangements can be
made by different relative positions of stops 457, 467 that control the travel
of end 432.
Since switch 400 includes second cooperating fiber 450, another arrangement is
advantageously made. When end 432 of steerable fiber 430 is in the rest
position of no
alignment with fiber 440, it can exchange light substantially efficiently with
end 452 of
second cooperating fiber 450.
The advantage in this arrangement is that a single action of turning switch
418
ON or OFF can connect fiber 430 with either fiber 440 or fiber 450.
Another feature of the invention is that ends 442, 452 are not parallel to
each
other, contrary to what prior art teaches. In fact, they define a nonzero
angle 0 between
them. More particularly, end 442 of first cooperating fiber 440 is at a first
exchanging
direction, when exchanging light with steerable fiber 430, and end 452 of
second
cooperating fiber 450 is at a second exchanging direction when exchanging
light with
steerable fiber 430. The first exchanging direction is at a nonzero angle 8
from the
second exchanging direction.
This feature permits better coupling by bending fibers 440, 450 less than that
of
the prior art, e.g. as seen in fibers 132, 134 of Fig. 1. It also permits
exchanging light
between 440, 450 and fiber 430 with less loss.
One more feature of the invention is that end 432 of steerable fiber 430 may
be
separately optionally prebiased with respect to the rest position. .This is
what enables
switching coupling between two fibers with a single action.
In the case of switch 400, steerable fiber 430 is mounted such that end 432 is
bent
when at the first position. This way, steerable fiber 430 is prebiased by an
internal fiber
tensile force, which tends to keep the fiber straight. That force therefore
resists bending,
and tends to return steerable fiber 430 to the rest position. From the rest
position,
steerable fiber 430 may couple light with second cooperating fiber 450.
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The invention thus takes advantage of one of the properties of optical fibers
made
from quartz. Such fibers have no "memory" of being bent, and always return to
their
shape. This way the switch does not lose efficiency after some time.
In other words, steerable fiber 430 is always bent, but less in the rest
position
S (coupling with fiber 450) than in the first position (coupling with fiber
440). This is
represented by steerable fiber 430 being shown mounted at an angle to a wall
of bottom
half 404 of the capsule.
In the case of switch 400, a stop 457 may present a groove for end 432 to be
pushed in, by the internal fiber tensile force. End 452 of second cooperating
fiber 450
may also be in the same groove, to better secure alignment. Stop 457 is
advantageously
mounted in bottom half 404 of the capsule.
Equally, when switch 418 is closed (as in Fig. 4C), another stop 467 may
provide
a meeting place for fiber ends 432, 442. Stop 467 is not shown in Fig. 4A, so
as not to
obscure salient featares.
Refernng now to Fig. 5A, a fiber-to-fiber switch 500 is shown, made according
to
another embodiment of the invention. It will be recognized that switch 500
includes
many elements similar to those of switch 400, whose detailed description will
therefore
not be repeated in detail.
Switch 500 includes a capsule made from a bottom half 504 and a top half 506.
They are intended to be closed together, thus defining an interior 508 of the
capsule.
Switch S00 includes a first electromagnet 510 similar to electromagnet 410.
First
electromagnet 510 may be implemented inside or outside the capsule, similarly
to
electromagnet 410. First electromagnet 510 is controlled by a switch S 18,
similar to
switch 418.
Switch 500 moreover includes a first pair of pole pieces 520, similar to first
pair
of pole pieces 420. As per the above, first pair of pole pieces 520 may go
through a wall
of the capsule.
Switch 500 also includes a first fixed magnet 522, which is made from a
permanent magnet. Magnet 522 is called fixed because of its close cooperating
relationship with pole pieces 520. Indeed, first fixed magnet 522 generates
the first
magnetic field in cooperation with first electromagnet 510. In other words,
the fields
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cooperate. The field of first fixed magnet 522 is transferred by first pair of
pole pieces
520 to a location inside the capsule, along with the field from the coil, when
generated.
Switch 500 additionally includes a steerable fiber 530, having an end 532 in
the
capsule. Steerable fiber 530 is similar to steerable fiber 430.
5 Switch 500 further includes an armature 535, similar to armature 435, and
attached to steerable fiber 530 near end 532.
Switch 500 moreover includes at least one cooperating fiber 540, having an end
542 in the capsule, and a second cooperating fiber 550, having an end 552 in
the capsule.
Referring now also to Fig. 5B, and Fig. SC, the operation of switch 500 is
10 described.
In Fig. 5A, Fig. 5B, switch 518 is open, and the first magnetic field is not
generated. Accordingly, armature 535 is not biased from the pole pieces 520,
and end
532 of steerable fiber 530 is at a rest position.
A feature of switch 500 is that end 532 of steerable fiber 530 is separately
prebiased with respect to the rest position. A permanent prebiassing magnet
560
generates a separate prebiasing field, to prebias armature 535. This makes for
secure
coupling, so that end 532 is aligned with end 552 of second cooperating fiber
550. There
end 532 can exchange light substantially efficiently with end 552.
Magnet 560 is mounted in the capsule in any suitable way. Its strength is
ideally
enough to maintain steerable fiber 530 at the rest position, where there is
coupling. This
way, no electric current is needed to maintain a magnetic field, and better
savings are
realized.
Alternately, magnet 560 is mounted outside the interior 508 of the capsule.
Pole
pieces may or may not be provided to transfer its field to a location close to
armature 535.
In Fig. SC, switch 518 is closed, and the first magnetic field is generated,
overcoming the prebiasing field of permanent prebiassing magnet 560.
Accordingly,
armature 535 is biased, and end 532 of steerable fiber 530 is moved to a first
position.
There end 532 is aligned with end 542 of first cooperating fiber 540, and can
exchange
light substantially efficiently with it.
Permanent prebiassing magnet 560 makes it so that a single action of turning
switch 518 ON or OFF can connect fiber 530 with either fiber 540 or fiber 550.
This
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way, steerable fiber 530 need not be bent by its mode of mounting, and may be
mounted
such that it is perpendicular to a side wall of bottom half 504 of the
capsule.
For both positions, appropriate stops 557, 567 with grooves may provide
meeting
places for fiber end 532 to meet with fiber ends 542, 552.
Referring now to Fig. 6A, a fiber-to-fiber switch 600 is shown made according
to
a third embodiment of the invention. It will be recognized that switch 600
includes many
elements similar to those of switch 400, whose detailed description will
therefore not be
repeated.
Switch 600 includes a capsule made from a bottom half 604 and a top half 606.
Top half 606 normally closes down on bottom half 604, thus defining an
interior 608 of
the capsule.
Switch 600 also includes a first electromagnet 610 for selectively generating
a
first magnetic field. First electromagnet 610 is controlled by a switch 618.
First electromagnet 610 is outside the capsule, although that is not
necessary.
First electromagnet 610 may equivalently be implemented to be within the
capsule.
A first pair of pole pieces 619 transfer the first generated magnetic field
from first
electromagnet 610 to a first transferred field location inside the capsule.
Pole pieces 619
are at least in part inside the capsule. In fact, they may go through a wall
of the capsule.
Switch 600 moreover includes a second electromagnet 620, for selectively
generating a second magnetic field. Second electromagnet 620 is controlled by
a switch
628.
Second electromagnet 620 is outside the capsule, although that is not
necessary.
Second electromagnet 620 may equivalently be implemented to be within the
capsule.
A second pair of pole pieces 629 transfer the second generated magnetic field
from second electromagnet 620 to a second transferred field location inside
the capsule.
Pole pieces 629 are at least in part inside the capsule. In fact, they may go
through a wall
of the capsule. Pole pieces 629 are similar to pole pieces 619.
Switch 600 additionally includes a steerable fiber 630, similar to steerable
fiber
430. An armature 635, similar to armature 435, is attached to steerable fiber
630.
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Switch 600 further includes at least a first cooperating fiber 640 and a
second
cooperating fiber 660. Light may be exchanged between steerable fiber 630 and
either
one of cooperating fibers 640, 660.
A feature of switch 600 is that the end of steerable fiber 630 is not
prebiased. It
has a rest position between cooperating fibers 640, 660. Biasing is needed for
steerable
fiber 630 to become aligned with either one of cooperating fibers 640, 660.
When at the rest position, a tip of the end of steerable fiber 630 does not
contact
the capsule. In fact, armature 635 is cantilevered on steerable fiber 630
without
contacting the capsule. This is especially possible from the little
appreciated property of
fused silica fibers that they never lose their shape, even in the face of
persistent bending.
Referring now also to Fig. 6B, Fig. 6C, and Fig. 6D, the operation of switch
600
is described.
In Fig. 6A, Fig. 6B, switches 618, 628 are open. Neither the first nor the
second
magnetic field are generated. Accordingly, armature 635 is not biased, and the
end of
steerable fiber 630 is at the rest position.
In Fig. 6C, switch 618 is closed, and switch 628 is open. Accordingly, the
first
magnetic field is generated, but not the second. This biases armature 635, and
the end of
steerable fiber 630 is moved to a first position of alignment with fiber 640,
where they
can exchange light.
In Fig. 6D, switch 618 is open, and switch 628 is closed. Accordingly, the
second
magnetic field is generated, but not the first. This biases armature 635, and
the end of
steerable fiber 630 is moved to a second position of alignment with fiber 660,
where they
can exchange light.
As before, in both cases suitable stops confine the travel of the free end of
steerable fiber 630, so that coupling is achieved. These stops are not shown
in Fig. 6A,
so as not to obscure salient features.
Referring now to Fig. 7, a flowchart 700 is used to illustrate a method
according
to an embodiment of the invention. Elements of the method of flowchart 700 may
also
be practiced by devices 400, 500 and 600 described above.
According to a box 710, light is received from an end of a steerable fiber.
This
would be the remote end from the switch, the end not shown in Figs 4A, SA, 6A.
Such
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light may be received on a continuous basis, and be either always on, or be
switching ON
and OFF to transmit digital signals.
According to a next box 720, the received light is output from the other end
of the
steerable fiber, in other words the end that is inside a capsule.
According to an optional next box 725, the received light is coupled into a
second
cooperating fiber, upon exiting from the _steerable fiber. That is in the
case, for example,
of where in device 400 fiber 450 is indeed provided.
According to a next box 730, a first magnetic field is generated, and
transferred to
the capsule interior. Transferring is advantageously performed by pole pieces.
The
steerable fiber is steered to a first position, responsive to the transferred
magnetic field. It
is enough if only the end of the steerable fiber is thus moved.
According to a next box 740, the received light is coupled into a first
cooperating
fiber. This is a result of moving the steerable fiber to the first position.
If, at box 725 the
received light was being coupled into a second cooperating fiber, that is
discontinued.
According to a next box 750, generation of the first magnetic field is
discontinued. This could be for switching a switch for another signal.
Accordingly,
biasing from the first magnetic field is also discontinued.
According to an optional next box 755, the steerable fiber is permitted to
move to
a rest position, as a result of discontinuing biasing from the first magnetic
field. This will
discontinue coupling light into first cooperating fiber, since the steerable
fiber moves
away from the first position. When at the rest position, the fiber may couple
the received
light into the second cooperating fiber.
According to a next box 760, a second magnetic field is generated, and
transferred
to the capsule interior. Transferring is advantageously performed by pole
pieces. The
steerable fiber is thus steered to a second position, responsive to the
transferred magnetic
field. It is enough if only the end of the steerable fiber is thus moved.
According to a next box 770, the received light is coupled into another
cooperating fiber, as a result of being in the second position.
In addition, the method described above is for a 1x2 switch. The process
equivalently reversed for 2x1 switch.
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Referring now to Fig. 8, parts of a switch 800 are shown. These parts may also
be
used in devices 400, 500, 600.
Switch 800 may be established in a bottom half 804 of a capsule. A top half
(not
shown) may be added later.
An optical bench 812 may be placed in bottom half 804. Pedestals 814, 816, 818
are provided on bench 812.
A steerable fiber 830 is provided in a pedestal 814. Its output end terminates
inside the capsule, and has an armature 835. Armature 835 may be biased by
magnetic
field transferred into the capsule by pole pieces (not shown).
Two cooperating fibers 840, 860 are mounted on pedestal 816, at a nonzero
angle
0. This angle is actually very small, about a few degrees. It is shown large,
to better
emphasize the aspect.
Fibers 830, 840, 860 are thus mounted on the pedestals, and designed for end-
to
end coupling. The end of fiber 830 is brought very close to that of fiber 860
(solid line).
In the other switching position, the end of fiber 830 is brought very close to
that of fiber
840 (dashed line).
A bench 818 supports structure needed to ensure secure the coupling. This
structure may include properly positioned grooves, etc.
Bench 812 may be made from fused silica. This results in the same temperature
expansion coefficient as the fibers. As temperature changes, so does the
distance
between the pedestals, but not the distance between the fibers. Accordingly,
the fiber
ends may be brought very close, for better coupling.
Referring now to Fig. 9, a detail of steering fiber 830, made according to the
invention.
Longitudinal optical fiber 830 is suitable for waveguiding light. Fiber 830
has an
output end 832. It may be made from fused silica, as is known for fibers.
Fiber 830 includes a substantially spherically shaped armature 835, attached
near
output end 832. Armature 835 is made from a material responsive to a magnetic
field, for
selectively steering output end 832. Preferably, armature 835 is spherically
shaped.
Armature 835 need not be a magnet. It may be made by forming a drop of liquid
glue around the fiber, suspending metal particles in the drop, and then curing
the glue.
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Alternately, armature 835 is a standalone magnet. For purposes of this
document
standalone magnet means either a permanent magnet, or a magnet made from
material
that has been subsequently magnetized.
A switch made according to the invention has shown very promising results. In
a
test of longevity, a 1-by-2 switch passed 500 million switching cycles without
a problem
and was still running smoothly.
Referring now to Fig. 10, an alternate design is shown according to the
invention.
A switch 1000 includes a pedestal 1018, similar to pedestal 818. Pedestal 818
has two
grooves 1022, which are horizontally disposed.
10 A fiber 1030 is to be placed into grooves 1022, to make contact with other
cooperating fibers (not shown). Fiber 1030 has an armature 1035, made
similarly to
armature 835, and is moved by magnetic fields.
A permanent prebiasing magnet 1040 exerts a field on armature 1035. This way,
permanent prebiasing magnet 1040 maintains steerable fiber 1030 in whichever
one of
1 S grooves 1022 it was last placed, without applying any current.
A first pair of pole pieces 1050 are designed to transfer a selectively
generated
vertical magnetic field, so as to overcome the field of permanent prebiasing
magnet 1040.
This way, they can lift steerable fiber 1030 out of groove 1022 by its
armature 1035,
along a vertical direction 1054. When the vertical magnetic field is no longer
generated,
permanent prebiasing magnet 1040 prevails, and moves armature 1035 downwards,
along
vertical direction 1054. An appropriate stop (not shown) may be used to
prevent
overtravel of steerable fiber 1030 and its armature 1035.
A second pair of pole pieces 1060 and a third pair of pole pieces 1070 are
designed to transfer selectively generated horizontal magnetic fields. This
way, they can
shift steerable fiber 1030 by its armature 1035 along a horizontal direction
1074. They
would do this preferably when steerable fiber 1030 has been lifted out of the
one of
grooves 1022 that it was placed in, for being aligned with the other. Lifting
would take
place along vertical direction 1054, as described above. Again, appropriate
stops (not
shown) may be used to prevent overtravel of steerable fiber 1030 and its
armature 1035.
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16
Switch 1000 may be optimized in a number of ways. For example, one of pairs of
pole pieces 1060, 1070 may be substituted by a permanent magnet. For another
example,
three grooves 1022 may be used instead of two.
In other improvements, a single armature may be used for two fibers.
Referring to Fig. 11, a steerable fiber 1132 and an auxiliary steerable fiber
1134
share a common armature 1135. They are to be coupled in various combinations
with at
least one of cooperating fibers 1142, 1144, 1146. Coupling is over a pedestal
1118,
having groves 1122.
Pairs of pole pieces 1160 and 1170 are designed to transfer selectively
generated
horizontal magnetic fields. This way, they can shift the pair of steerable
fiber 1132 and
auxiliary steerable fiber 1134 by their shared armature 1135, and guide it to
the right pair
of groves 1122.
A person skilled in the art will be able to practice the present invention in
view of
the description present in this document, which is to be taken as a whole.
Numerous
details have been set forth in order to provide a more thorough understanding
of the
invention. In other instances, well-known features have not been described in
detail in
order not to obscure unnecessarily the invention.
While the invention has been disclosed in its preferred form, the specific
embodiments as disclosed and illustrated herein are not to be considered in a
limiting
sense. Indeed, it should be readily apparent to those skilled in the art in
view of the
present description that the invention may be modified in numerous ways. The
inventor
regards the subject matter of the invention to include all combinations and
subcombinations of the various elements, features, functions and/or properties
disclosed
herein. For example, a switch may be made with combinations of elements from
switches 400, 500, 600. Plus, switch 600 can have a second fixed magnet to
generate the
second magnetic field in cooperation with the second electromagnet, and so on.
The following claims define certain combinations and subcombinations, which
are regarded as novel and non-obvious. Additional claims for other
combinations and
subcombinations of features, functions, elements and/or properties may be
presented in
this or a related document.
