Note: Descriptions are shown in the official language in which they were submitted.
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Optical Switch
Field of the Invention
The present invention relates to an nxm optical switch for use in an optical system
such as a switching network, n being > 1, m> 1.
Background of the Invention
Optical matrix switches, for example, nxm optical switches, are capable of connecting
0 one or more input fibers to any one of a number of optical output fibers by reflecting a signal
on a selected one of an array of reflective means. Usually an array of parallel input optical
fibers are arranged orthogonal to an array of parallel output optical fibers; however these
switches are usually bi-directional such that all ports can function as input/output ports.
Movable or state ch~nging reflective means are arranged at each of the intersections between
the optical paths launched from input and output fibers for selectively coupling a signal from
an input fiber to a desired output fiber. Switches of this type are constructed using a wide
variety of structures, including mechanical, opto-electronic and magnetic actuation. An nxn
optical matrix switch of this type requires n2 reflective means to allow n input ports to be
connected to n output ports in a non-blocking fashion.
United States Patent No. 4,988,157 to Jackel et al. herein incorporated by reference,
discloses an nxm optical matrix switch having slots at 45 degrees to orthogonal waveguides.
The slots are filled with a liquid that matches the refractive index of the waveguides.
Electrodes positioned adjacent to the slots form gas bubbles in a selected slot by electrolysis.
One of the electrodes catalyses the reformation of the liquid from the bubble components
when a voltage pulse is applied. Light in the input waveguides is transmitted through an
intersection in the presence of liquid, but is reflected into an output waveguide in the
presence of bubbles.
Another nxm optical matrix switch is disclosed in United States patent No. 4,580,873
to Levinson. This mxn optical switch is formed on a semiconductor substrate. Grooves are
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etched at the edges of the substrate to accommodate input and output optical fibers so that the
output fibers are placed orthogonal to the light paths of the input fibers. At each cross point
defined by the input and output fibers, an electromechanically actuated mirror is provided
which in one position permits passage of light from its associated input fiber to a subsequent
s mirror, and in another position deflects the light to its associated output fiber.
Another example of a matrix switch is disclosed in United States patent No.
5,255,332 to Welch et al. The reflective means in this mxn optical switch matrix comprises
an array of gratings formed in a semiconductor heterostructure. The gratings have two states.
o When a refractive index change is induced, the Bragg condition for the light received from an
optical signal is met, and a portion of the light is diffracted from the row in which it is
propag~ting into a column toward another optical fiber. In the off state, if the incident light
does not satisfy the Bragg condition, the beam propagates unperturbed through the grating to
be sampled by a subsequent switch.
Switches vary in size from the minimum lx2 to very large matrixes exceeding
lOOxlOO.
Today, currently available switching matrices are being manufactured by use of a20 single stage architecture where both input and output sides of a P x P matrix are comprised of
1 x P rotary switches. A rotary switch of this type is described by Duck et al. in U.S. patent
4,378,144. Duck et al. propose an arrangement wherein a faceplate comprising a number of
collim~ting lenses along a pitch circle is attached directly to a stepping motor, the shaft of the
motor being coaxial with the pitch circle. A rotatable arm with a collim~tin~ le ns is attached
2s to the shaft for rotation along the pitch circle, with a small distance therebetween, so that the
lens of the arm can be optically connected with the lenses on the faceplate when the rotatable
arm is moved by means of the shaft of the stepping motor. An optical input fibre is
connected to the collim~ting lens (hereafter called a lens-to-fibre unit) of the arm and a
plurality of optical output fibres are attached to the respective collim~tin~ lenses on the
30 faceplate for a switching operation when the rotatable arm moves from one position to
another.
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Configuring a plurality of 1 x P rotary switches into a single stage PxP switch has the
following limitations:
s a) the cost of the switch is largely dependent upon the cost of the number lens-to-fibre units
required; and,
b) The maximum reconfiguration time of the component lxP rotary switch is directly
dependent upon the dimension of the matrix.
o It is usually preferable that optical switches be efficient, fast and compact. As
telecommunication networks have evolved over the years and have become more complex, a
need has arisen for a matrix switching system capable of optically coupling any one of a
large number of other fibers to another. Furthermore, it is desirable for the switching system
to be "non-blocking", i.e. the switching of one input fiber to an output fiber should not
interfere with the light tr~n.smission of any other input fiber to any other output fiber.
Another type of lxn optical switch has been disclosed by T a~lghlin in U.S. patents
5,555,327 5,444,801 5,333,175 5,555,558 and 5,566,260 wherein one input is switched to
any of a plurality of output locations or ports by placing a wedged shaped block of glass next
to a prism. Although T a~lghlin's switch may be useful, it appears to have several drawbacks.
For instance, the output beams that exit T a~lghlin's prism are non-parallel and non-
orthogonal to the prism face that they exit. It is believed that the coupling of the light exiting
at different angles is somewhat difficult. Furthermore, if T allghlin's wedge is moved slightly
out of position so that a beam incident upon the wedge goes through a thicker or thinner
2s portion than expected, the beam will not exit exactly where the light is being collected.
This invention obviates many ofthe potential problems associated with Lal1ghlin's
disclosed invention.
It is an object of this invention to provide an nxn optical switch, that for numbers of n
exceeding for example 4, would require less than n2 optical switching elements.
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It is also an object of this invention, to provide an optical switch that wherein a
standard gate can be used for each switching element, and wherein the switch requires less
than n2 optical switching elements to configure an nxn switch for n > 8.
Summary of the Invention
In accordance with the invention there is provided, an optical switch comprising:
a first deflector having a first port for launching at least a beam of light, said deflector having
o a plurality of light receiving locations;
switching means for switching a beam of light launched into the first port for selectively
directing said beam along one of a plurality of selectable paths defining a first plane to one of
the plurality of light receiving locations; and,
a second deflector having output locations, the second deflector being optically coupled with
15 the first deflector, the second deflector for directing light from one of the light receiving
locations to one of the output locations along at least a path defining a second plane, the first
plane and the second plane intersecting one another.
20 In accordance with the invention there is provided, an optical switch comprising:
a first deflector having a plurality of input ports for launching input beams of light, said
deflector having a plurality of light receiving locations;
switching means for switching beams of light launched into any of the input ports and for
selectively directing each of said beams along one of a plurality of selectable paths to one of
25 the plurality of light receiving locations, each plurality of selectable paths defining a plane,
said planes defined by said beams being parallel first planes; and,
a second deflector having output locations, the second deflector being optically coupled with
the first deflector, the second deflector for directing light from any one of the light receiving
locations to one of the output locations along at least a path defining a second plane
30 intersecting the parallel first planes.
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In accordance with the invention there is provided, an optical deflection switch comprising:
a first light tr~nsmi.~ive prism, having a plurality of input ports and having a plurality of
sequential deflection regions coupled thereto disposed to receive light launched into any of
the plurality of input ports, each deflection region having at least two selectable deflective
surfaces disposed, upon selection to reflect the light to a next sequential deflection region so
that a beam launched in at least one of the input ports follows one of a plurality of selectable
paths to one of a plurality of output locations;
means for selectively ch~nging the optical path length between deflections of the optical
path within sequential deflection regions;
o a second light tr~nsmi.~sive prism coupled to the first prism for substantially ch~nging the
direction of beams at the output locations and for directing said beams to output ports.
In accordance with the invention, there is provided, an optical deflection switch for
selectably switching any of n input signals to at least m output locations, comprising:
a first module including:
a first deflector having a plurality of deflecting surfaces for reflecting a plurality of
optical signals by total internal reflection;
n input ports about a face of the deflector, wherein n> 1,
a plurality of sequential deflection means disposed to receive light that has been
launched into at least some of the n input ports and that has passed through at least
some of the plurality of deflecting surfaces, each of said plurality of sequential
deflection means being operable to reflect said light to one of a next deflection
means, deflecting surface and an output location.
In accordance with the invention, there is further provided, an optical switch comprising:
a prism having n input ports and having a first plurality light reflective regions and a second
plurality of light reflective regions, each light reflective region in said first plurality being
disposed to receive light from one of the n input ports and to reflect the light to one of the
30 reflective regions in the second plurality of light reflective regions in a first mode of
operation;
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in a second mode of operation, light reflecting means in the first plurality being light
tr~n.~mi.~.~ive for allowing light to propagate therethrough; and,
a plurality of deflection means disposed adjacent the light reflective regions operable to
reflect light that has propagated through any of the first and second plurality of light
reflective regions, any of said n input ports being switchable to any of n output ports by
controlling the reflection of light launched into the input ports through selection of the first
mode or the second mode of operation.
In accordance with the invention, there is further provided, an optical deflection switch
I o comprising:
a light tr~n.~mi~ive material, having a plurality of input ports and having a plurality of
sequential deflection regions disposed to receive light launched into any of the plurality input
ports, each deflection region having at least two selectable deflective surfaces disposed, upon
selection to reflect the light to a next sequential deflection region so that a beam launched in
at least one of the input ports follows one of a plurality of selectable paths to one of a
plurality of output ports; and
means for selectively ch~ngin~ the optical path length between deflections of the optical
path within sequential deflection regions.
20 In accordance with the invention, there is provided, an optical deflection switch comprising:
a light tr~n~mi.~ive material, having a plurality of input ports and having a plurality of
sequential deflection regions coupled thereto disposed to receive light launched into any of
the plurality input ports, each deflection region having at least two selectable deflective
surfaces disposed, upon selection to reflect the light to a next sequential deflection region so
25 that a beam launched in at least one of the input ports follows one of a plurality of selectable
paths to one of a plurality of output ports; and
means for selectively ch~nging the optical path length between deflections of the optical
path within sequential deflection regions.
30 In accordance with the invention there is further provided, an optical deflection switch
comprising:
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a light tr~n~mi~ive material, having a plurality of input ports and having a plurality of
sequential deflection regions coupled thereto disposed to receive light launched into any of
the plurality input ports, each deflection region having at least two selectable deflective
surfaces disposed, upon selection to reflect the light to a next sequential deflection region so
5 that a beam launched in at least one of the input ports follows one of a plurality of selectable
paths to one of a plurality of output ports; and
means for selectively ch~nging the optical path length between deflections of the optical
path within sequential deflection regions.
o In accordance with a different aspect of the invention, a method is provided of switching an
optical signal from an input port to one of a plurality of output ports, comprising the step of:
launching a beam of light into the input port;
selecting a plurality of deflections along a first plane to direct the beam along the first plane
to one of a plurality of output locations;
5 receiving the beam from one of the plurality of locations and directing the beam along a
second plane intersecting the first plane, to direct the beam to one of the output ports.
Brief Description of the Dr~. ingS
Exemplary embodiments of the invention will now be described in conjunction with the
drawings in which:
Fig. 1 is a schematic block diagram of a prior art conventional 8x8 non-blocking optical
25 switch formed from 16 lx8 optical switch blocks;
Fig. 2 is a detailed schematic block diagram of' a prior art single lx8 block formed from lx2
optical switches;
Fig. 3 is a schematic block diagram of a prior art 4x4 optical matrix switch having 16
movable reflective elements;
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Fig. 3a is an illustrative diagram of a binary optical deflection switch having a single input
port and eight output ports;
s Fig. 3b is an illustrative diagram of a binary optical deflection switch having a single input
port and two output ports in accordance with the invention;
Fig. 4 is a schematic block diagram of a 4x4 optical switch in accordance with an
embodiment of this invention;
Fig. S is a broken away side view of a portion of the switch shown in Fig. 4 wherein the
switching element is shown in greater detail;
Fig. 5a a is a broken away view of a portion of an optical switch having different switching
elements than in Fig. 5;
Fig. 5b is a detailed diagram of a switching element shown having its two normally directly
coupled components separated;
20 Fig. 5c is a diagram illustrating the mechanism for moving the fluid contained within a tube;
Fig. 6 is a diagram illustrating the light paths through a prism shown in Fig. 4;
Fig. 7 is a side view of an alternative embodiment of the invention, wherein switching
25 elements are disposed within a glass prism;
Fig. 8 is diagram illustrating an embodiment of the invention wherein fewer switching
elements are provided than in the embodiment of Fig. 4, however the switch is a blocking
switch;
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Fig. 9 is a diagram illustrating an alternative embodiment of the invention wherein a prism
having switching elements is optically coupled with a prism absent switching elements; and,
Fig. 10 shows an embodiment similar to the one shown in Fig. 9, however an additional
s prism is directly optically coupled with a larger prism.
Detailed Description
Referring now to Fig. 1, a single stage switched distribution, switched recombination (SDSR)
o design is shown wherein each port 12 is connected to a lxP rotary fibre switch, as is
described by Duck et al. mentioned above, where P is the overall dimension of the matrix. As
is illustrated, optical fibres couple each switch on one side of the matrix to each switch on the
other side of the matrix. There are 2P switches including a total of 2P(P+1 ) lensed fibre
units. Therefore the single stage 8 x 8 matrix shown in Fig. 1 includes a total of 16 lx8 rotary
switches 10 including 144 lensed fibre units.
Alternatively, each of the lx8 switches can be formed of 7 lx2 optical switches configured as
shown in Fig. 2. Thus to achieve the architecture shown in Fig. 1, 2n(n-1) = 112 lx2 optical
switches would be required.
Turning now to Fig. 3 a 4x4 optical matrix switch 30 is shown having 16 movable reflective
elements 32. It should be noted that an 8x8 optical switch of a similar architecture requires
64 reflective elements 32.
2s Referring now to Fig. 3a, a binary optical deflection switch is shown comprised of a
trapezoidal shaped block 10 having an input port 6 and having output ports 7a to 7h, wherein
ports 7a, 7g, and 7h are shown. The block 10 is made of light tr~n~mi~sive material such as
glass. Light tr~n~mi~sive glass blocks 12, 14 and 16 having three different thicknesses t, 2t,
and 4t and having the same refractive index as the trapezoidal shaped block 10 are shown to
30 be adjacent the block 10, and spaced from the block 10 by a thin layer of silicone 15 having a
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refractive index that is substantially the same as the glass blocks or an equivalent resilient
index matching buffer material.
A more basic 1 x2 optical switch is shown in Fig. 3b having a single input port and two
5 output ports. An input beam is launched from the left of the figure into a block of glass 6.
When the glass block 7 (and its buffer material not shown) is optically contacting the block
6, light is routed to port 1. When the glass block 7 is moved so that it does not contact the
block 6, light is routed to port 0. The thickness t of the block 7 will determine the spacing
between ports 0 and 1. It is noted that the altemate optical paths to the ports 0 and 1 are
o parallel paths. By using the light transmissive blocks 12, 14, and 16 as shown, and having
parallel alternate paths between sequential reflective regions, the 8 output ports 0, ... 5, 7
shown in Fig. 3a are evenly spaced. This becomes even more important in the nxn optical
switch described hereafter.
The operation ofthe switch can now readily be understood with reference to Fig. 3a and lb.
Although not shown, the blocks 12, 14, and 16 are individually controllably movable such
that they are in contact with the block 10 (via the elastomer index matching material) or such
that they are lifted off of the block 10. By way of example, several, but not all of the possible
selectable paths are shown through the lines 1 8a, 1 8b, and 1 8c which lead to ports 0, 5, and 7
respectively. As a beam of light 18 is launched into the input port 6 of the switch at a
predetermined angle, it is either reflected off the air/10 interface or the air/12 interface,
depending upon whether block 12 is not, or is, in contact (via the elastomer) with block 10.
In the first instance when there is contact between the blocks 10 and 12, the bearn 18 reflects
off the outward face of the block 12 and follows the path shown by dotted line 1 8b. In the
second instance when there is no contact between the blocks 10 and 12, the beam 18 reflects
off the face 10 and follows the path defined by line 1 8a. Depending upon whether blocks 14
and 16 are lifted off or are in contact with the block 10 will determine which path is
followed. The positioning ofthe blocks 12, 14, 16 adjacent sequential reflective surfaces of
the block 10 is determined by the initial launch angle. It should be noted that for a switch
with n blocks (i.e. here n=3 for blocks 12, 14, and 16), that there are 2n output ports. For
example in this instance, where n = 3, the following switching combinations are possible.
.,
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12 14 16
off off off
off off on
5 off on off
off on on
on off off
on off on
on on off
o on on on
In another embodiment of the invention, the blocks 12, 14, and 16 can be stationary and can
be selectively filled with an index matching fluid or filled with air to allow tr~n.cmi~ion or
reflection upon selection thereof. This switching actuation is described in greater detail in
5 reference to Figs. 4 to 10. It should be noted that in Fig. 3a selectable optical paths from the
block 12 to the block 14 are parallel and selectable optical paths from the block 14 to 16 are
also parallel to one another. Conveniently, this parallelism ensures that the output beams will
also be parallel to one another making the coupling of the output light considerably easier.
Although this embodiment is believed to be an improvement over Laughlin's switch which
20 relies on using a wedge, one disadvantage of this embodiment that is obviated in the switch
shown in Fig. 4, is that the blocks 12, 14, and 16 must increase in thickness for the receiving
output ports to be evenly spaced. For a 1 x64 switch this requires blocks of substantial
thickness. In the embodiment of Fig. 4, which is a folded configuration, the difficulty is
obviated.
In Fig. 4 a first diffractor 41a in the form of a light tr~n.cmi.c.cive prism is optically coupled
with a second diffractor 41b in the form of a second light tr~n~mi.c~ive prism disposed at right
angles to the first diffractor 41 a. By positioning the prisms at right angles, the switch can be
considerably small allowing an array of input beams to be switched in a first direction to a
30 plurality of intermediate locations, and subsequently in an orthogonal direction to a plurality
of output ports, thereby providing a 4x4 non-blocking switch. Four input ports 1 a through 4a
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are disposed along an upper face of the prism 41 a. However, it should be noted that if ports
2a through 4a were not provided as is shown in Fig. 9b, a lxI6 optical switch would result.
In Fig. 4, these ports are formed by coupling four input optical fibres to four predetermined
5 locations about the face of the prism 41 a using standard optical fibre tube coupling
technology. Similarly the output ports 1 b through 4b are formed along a lower face of the
second diffractor 41 b. The presence of controllable two-state optical switching elements are
generally shown as longitudinal rectangular regions at 1 Oa, through 1 Od, 20a through 20d,
30a through 30d, and 40a through 40d and will be described with reference to Fig. 5 in
o greater detail with reference to switching elements lOa and 20a. Element lOa shown, and
elements lOb to lOd not shown, each have a standard switching block 52 sandwiched
between an outward face ofthe prism 41a and a glass block 54a having a thickness of"d"
units. The distance "d" is selected in dependence upon the required spacing between the ports
on one side of the device. A similar arrangement is shown at the next switching element 20a
s and each of switching elements 20b to 20d (not shown) wherein a standard switching block is
sandwiched between an outside face of the prism 4 lb and a glass block 54b having a
thickness of"2d" units. The second prism 41b also has similar switching elements each
having a standard switching block 52. Advantageously, the row of elements 30a to 30d each
have a glass block of thickness "d" and the row of elements 40a to 40d each have a glass
20 block of thickness "2d" adjacent a switching block 52, wherein in a linear switch that is not
folded by a second prism being orthogonal to the first prism as is the case in this
embodiment, the thickness of the glass blocks must increase at each subsequent element. By
providing blocks 54a, 54b, 54c, and 54d with different thicknesses a beam launched into the
port la the beam can be switched to different positions A, B, C, or D as shown in Fig. 5 by
2s controlling the two switches 1 Oa and 20a. Of course any of the input ports can be switched
to any of the output ports of this bi-directional switch by switching blocks 52 to achieve this
end.
Each standard switching block 52 used for each of the 2nLog2n switches are made of a light
30 tr~n~mi~sive material preferably having a same refractive index as the prism. Each block 52
has therewithin a cavity into which an refractive index matching liquid is pumped in a first
, . ~
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tr~n~mi~sive switching mode. In the first switching mode light incident upon the block 52 is
transmitted therethrough. Alternatively in a second deflecting switching mode at least some
of the index matching fluid is expelled from the cavity so that air is within the cavity and
light incident upon the block 52 from the prism is deflected to a next serial block 52.
An alternative embodiment of the switching element is shown in Fig. 5a, wherein a light
deflecting region includes a switching element in the form of a glass block 52a having a
conduit or longitudinal bore along its length. Another glass block 52b of a first dimension
"d" or 52bb of dimension substantially about "2d" is placed directly on top of the block 52a.
o In this manner a standard block 52a can be used and blocks of appropliate thicknesses can be
directly coupled on top. Inlet and outlet conduits in the form of tubes 52aa are used to move
index matching fluid and the air bubble shown through the longitudinal bore within 52a as is
required. In operation when a beam launched into the switch is incident upon the bubble, the
beam is reflected as is shown in the switch block 52a on the right of the figure; alternatively,
5 as is shown on the left, when the beam is incident on the index matching fluid, the beam is
transmitted through the longitudinal bore.
Fig. 5c illustrates the mechanism for moving the fluid contained within the tube 52aa. The
exemplary embodiment depicts a solenoid, which can be actuated to move the fluid within
20 the circuit shown, defined by the longitudinal bore and the tube 52aa.
The operation of the optical switch of Fig. 4 can more readily be understood while referring
to Fig. 5c. However for ease of underst:~n-ling the operation Fig. 5c is shown to have 3
input/output ports and 4 output/input ports instead of the 4 inputs and 4 outputs shown in the
25 4x4 switch as shown in Fig. 4. The input port in/out 1 can provide its output signal to any one
of 4 output locations shown in the row facing the port. Similarly each of the ports in/out2,
and in/out3, can provide an output signal to one of 4 output locations depending upon the
selection of the switches. It can be seen that the switch is folded to allow any of the beams in
the direction from the port in/outl destined for one of the 4 output ports in the row facing the
30 port in/outl to be routed orthogonally to one of the output ports.
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g. 6 shows in more detail the alternative paths an input beam may be routed along in
switching from a first input port to one of four output locations at an upper face of the prism
41 a. Depending upon the state of the first switching element 52 (not shown in Fig. 6), an
input beam launched into the first port la can be reflected at location 60a or to the location
61a. Depending upon the state of the second switching element, one of the two beams
reflecting from 60a or 61a can be reflected at locations 61b, 61bb, or 60bb or 60b, thereby
providing 1 to 4 switching. Simultaneously, 1 to 4 switching can independently occur for
other light beams launched into ports 2a, 3a, and 4a. In this manner 4 input beams can be
switched (in a semi-blocking manner) to 16 output locations 66 shown in dotted outline.
0 However the 4 input beams can be switched in a non-blocking manner to 4 output locations.
Referring once again to Fig. 4, the second prism 41b provides a means of directing light
launched into all of the input ports to any of the 16 output locations 66 shown in Fig. 6 and to
any of the output ports lb, 2b, 3b, or 4b, in a non-blocking manner. With the exception of the
thickness "4d" and "8d" of the glass blocks 54c and 54d respectively, being different than
thickness of the blocks 54a and 54b, the prisms 41a and 41b including switching elements
are identical. Of course the ports 1 b to 4b must be accurately optically aligned with the input
ports la to 4a
20 In operation, light launched any of the ports 1 a through 4a can be switched to any of ports 1 b
through 4b by controlling ~ppropliate switching elements 52. Alternatively light launched
into any of ports lb through 4b can be switched to ports la through 4a through control of the
switching elements 52, thereby providing an nxn non-blocking compact bi-directional optical
switch having no movable switching elements. Switching is accomplished by the removal or
2s insertion of a fluid into the cavity within a switching element 52.
In an alternative embodiment shown in Fig. 7, the switching elements can be formed within
a prism 71 by boring channels 74 parallel to adjacent sides of the prism 71 that can be filled
with a fluid or have fluid evacuated therefrom to switch between tr~n~mi~.~ive and deflective
30 switching modes of operation. One of the switching elements 74 is shown to be closer to its
..
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adjacent side than the other element 74. This variation in distance allows a single input beam
to be switched to any of four output positions A, B, C, and D.
Although the embodiments described heretofore in accordance with the invention provide
non-blocking switching of optical signals, the embodiment shown in Fig. 8 depicts a
blocking version of the 4x4 optical switch. In this embodiment only four switching elements
110, 120, 130, and 140 are required similar to, but wider than elements lOa, 20a, 30a and 40a
shown in Fig. 5. Each of the elements 110 through 140 requires a switching blocksandwiched between a face of the prism and a light tr~n~mi~ive block of a predetermined
o thickness.
Fig. 9 shows yet an alternative embodiment of a 4x4 non-blocking optical switch. Here
instead of using an identical block 41 b having switching elements thereon, as is shown in
Fig. 4, the same functionality is provided by using a deflector prism 90 angled such that light
at the 16 output locations 66 are deflected to 16 output locations 96. Four additional
switching elements 1 Oe through 1 Oh and 20e through 20h (not shown) are required at two
faces of the prism adjacent to the elements 1 Oa through 1 Od and 20a through 20d to direct
light from any of the output locations 96 to any of the output ports 90. Thus, by controlling
the 16 switching elements any beam launched into any of ports 1 a through 4a can be coupled
20 to any of ports lb through 4b.
Referring now to Fig. 9b, a diagram is shown of a 3x4 switch of the type in Fig. 9. The prism
90 is shown to transpose beams at the output locations 91a adjacent the input/output
waveguides by providing the beams at the adjacent array of locations 91b.
Fig. 10 shows an embodiment similar to the one shown in Fig. 9, however an additional
prism 100 is directly optically coupled with the larger prism 41 a. Input/output ports 1 a to 8a
and output/input ports 1 b to 8b are disposed at an end face of the prism 100. The diagram
illustrates a path of a beam launched into port 1 a as it propagates through prisms 100, 41 a
30 and 90 to reach output/input port lb. The beam launched into port la is shown as a dotted
line and entering the location 66a from the below to exit upward to the prism 90. The prism
. .. ~ ,~
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90 reflects (and maps) the beam to a similar location 96a on the array of locations 96. The
beam then enters location 96 from above and is then directed to output/input port lb shown
by a dashed line.
5 In all of the embodiments shown, means in the form of a prism 90 shown in Figs 9 and 10 or
the prism 41b as is shown in Fig. 4 provide a means of ch~ngin~ the direction of a plurality
of beams launched into an input port directed to a plurality of first selectable locations so as
to physically map those locations to a second plurality of selectable locations that are
selectably optically alignable with a plurality of output ports.
16
