U.S. patent application number 09/988539 was filed with the patent office on 2002-05-23 for optical switch.
Invention is credited to Ducellier, Thomas.
Application Number | 20020061158 09/988539 |
Document ID | / |
Family ID | 25682237 |
Filed Date | 2002-05-23 |
United States Patent
Application |
20020061158 |
Kind Code |
A1 |
Ducellier, Thomas |
May 23, 2002 |
Optical switch
Abstract
The invention provides and optical switch having a first
plurality of independently moveable deflectors with a first optical
bypass for allowing the beam of light launched into an input port
to pass therethrough, and a second plurality of independently
moveable deflectors with a second optical bypass for allowing the
beam of light to pass therethrough to any one of a plurality of
output ports, said second plurality of independently moveable
deflectors being disposed so as to receive the beam of light that
passed through the first optical bypass, and wherein a switching is
carried out by the first and second plurality of independently
moveable deflectors. The optical elements are disposed about a
common optical axis. Advantageously, the optical switch includes
relay lenses for directing the light beam to the first optical
bypass and for receiving it from the second optical bypass and
directing it to the output ports. Furthermore, an ATO element can
be disposed between first and the second plurality of independently
moveable deflectors.
Inventors: |
Ducellier, Thomas; (Ottawa,
CA) |
Correspondence
Address: |
Juliusz Szereszewski
JDS Uniphase Corporation
570 West Hunt Club Road
Nepean (Ottawa)
ON
K2G 5W8
CA
|
Family ID: |
25682237 |
Appl. No.: |
09/988539 |
Filed: |
November 20, 2001 |
Current U.S.
Class: |
385/17 ;
385/18 |
Current CPC
Class: |
G02B 6/3556 20130101;
H04J 14/02 20130101; H04Q 2011/0024 20130101; G02B 6/32 20130101;
H04Q 2011/003 20130101; G02B 6/356 20130101; H04Q 11/0005 20130101;
H04Q 2011/0015 20130101; H04Q 2011/0037 20130101; H04Q 2011/0035
20130101; H04Q 2011/0052 20130101; H04Q 2011/0043 20130101; G02B
6/3512 20130101; G02B 6/3562 20130101; H04Q 2011/0026 20130101 |
Class at
Publication: |
385/17 ;
385/18 |
International
Class: |
G02B 006/35 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 20, 2000 |
CA |
2,326,362 |
Dec 6, 2000 |
CA |
2,327,862 |
Claims
What is claimed is:
1. An optical switch comprising: at least one input port for
launching a beam of light into the optical switch; at least two
output ports for selectively receiving a beam of light; a switch
core in optical communication with the at least one input port and
the at least two output ports; at least a first optical bypass,
disposed at the switch core, comprising a first transmissive point
through which output beams pass out of the switch core, said output
beams substantially overlap each other at the first optical bypass;
and a plurality of beam deflectors disposed in the switch core for
switching the beam of light from the at least one input port to a
selected one of the at least two output ports through the
transmissive point of the at least first optical bypass.
2. The optical switch as defined in claim 1 wherein the at least
first optical bypass is in optical communication with the at least
one input port for allowing input beams to pass into the switch
core via the first transmissive point.
3. The optical switch as defined in claim 2 wherein at least one of
the plurality of beam deflectors is an independently moveable beam
deflector.
4. The optical switch as defined in claim 3 wherein the plurality
of beam deflectors includes a first plurality of independently
moveable beam deflectors, said first plurality of independently
moveable beam deflectors being disposed on a first surface
comprising the at least first optical bypass.
5. The optical switch as defined in claim 1 further including an at
least second optical bypass for allowing at least one of input and
output beams to pass into and out of the switch core.
6. The optical switch as defined in claim 5 wherein the plurality
of beam deflectors includes a second plurality of independently
moveable beam deflectors, said second plurality of independently
moveable beam deflectors being disposed on a second surface opposed
to the first surface comprising the at least second optical
bypass.
7. The optical switch as defined in claim 6 wherein at least one of
the first and second surface is one of a planar and a spherical
surface.
8. The optical switch as defined in claim 7 wherein the at least
first optical bypass and the at least second optical bypass are
disposed along an axis of symmetry.
9. The optical switch as defined in claim 8 wherein the first
plurality of independently moveable beam deflectors is disposed
about the at least first optical bypass and the second plurality of
independently moveable beam deflectors is disposed about the at
least second optical bypass, said at least first optical bypass
being in optical communication with the at least one input port and
said at least second optical bypass being in optical communication
with the at least two output ports.
10. The optical switch as defined in claim 9 further including a
first relay lens disposed about the axis of symmetry between the at
least one input port and the first plurality of independently
moveable beam deflectors, said first relay lens for receiving a
beam of light from the at least one input port and for directing a
beam of light to the first optical bypass.
11. The optical switch as defined in claim 10 wherein the at least
one input port and the first plurality of independently moveable
beam deflectors are disposed near or at a focal plane of the first
relay lens.
12. The optical switch as defined in claim 10 further including a
second relay lens disposed about the axis of symmetry between the
second plurality of independently moveable beam deflectors and the
at least two output ports, said second relay lens for receiving a
beam of light from the at least second optical bypass and for
directing a beam of light to a selected one of the at least two
output ports.
13. The optical switch as defined in claim 12 wherein the second
plurality of independently moveable beam deflectors and the at
least two output ports are disposed near or at a focal plane of the
second relay lens.
14. The optical switch as defined in claim 13 wherein a focal
length of the first relay lens is approximately equal to a focal
length of the second relay lens.
15. The optical switch as defined in claim 8 further comprising an
ATO element, said ATO element being disposed between the first and
the second plurality of independently moveable beam deflectors
along the axis of symmetry, said axis of symmetry being an optical
axis of the ATO element.
16. The optical switch as defined in claim 15 wherein the ATO
element is for passing a beam of light three times therethrough
along an optical path between the at least one input port and a
selected one of the at least two output ports.
17. The optical switch as defined in claim 15 wherein the first and
the second plurality of independently moveable beam deflectors are
disposed near or at a focal plane of the ATO element.
18. The optical switch as defined in claim 17 wherein the ATO
element has a focal length approximately equal to a near zone
length or Rayleigh range of a beam of light incident thereon.
19. The optical switch as defined in claim 17 wherein the ATO
element is one of a lens and a mirror.
20. The optical switch as defined in claim 8 wherein the first
plurality of independently moveable beam deflectors and the second
plurality of independently moveable beam deflectors comprise an
array of micro-mirrors.
21. The optical switch as defined in claim 20 wherein the array of
micro-mirrors is one of a linear, rectangular, and radial
array.
22. The optical switch as defined in claim 9 further including at
least one micro-lens disposed at at least one of the at least one
input port and the at least two output ports.
23. The optical switch as defined in claim 22 wherein the at least
one input port and the at least two output ports are parallel to
the optical axis or radially disposed about the optical axis.
24. An optical switch comprising: at least one input port for
launching a beam of light into the optical switch; at least two
output ports for selectively receiving the beam of light; a first
plurality of independently moveable deflectors disposed about a
first optical bypass for allowing a beam of light launched from the
at least one input port to pass therethrough, and wherein input
beams passing through the first optical bypass are substantially
overlapping at the first optical bypass; and a second plurality of
independently moveable deflectors disposed about a second optical
bypass for allowing a beam of light to pass therethrough to any one
of the at least two output ports, said second plurality of
independently moveable deflectors being disposed so as to receive a
beam of light that has passed through the first optical bypass, and
wherein the first and second plurality of independently moveable
deflectors are adapted to switch a beam of light, and wherein
output beams passing through the second optical bypass are
substantially overlapping at the second optical bypass.
25. The optical switch as defined in claim 24 wherein the first and
second optical bypasses comprise a transmissive point through which
input and output beams pass into and out of the optical switch.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This applications claims priority from Canadian Patent
Application No. 2,326,362 filed on Nov. 20, 2000 and Canadian
Patent Application No. 2,327,862 filed on Dec. 6, 2000.
MICROFICHE APPENDIX
[0002] Not Applicable
FIELD OF THE INVENTION
[0003] The present invention relates to the field of optical
switches.
BACKGROUND OF THE INVENTION
[0004] Optical matrix switches are commonly used in communications
systems for transmitting voice, video and data signals. Generally,
optical matrix switches include multiple input and/or output ports
and have the ability to connect, for purposes of signal transfer,
any input port/output port combination, and preferably, for
N.times.M switching applications, to allow for multiple connections
at one time. At each port, optical signals are transmitted and/or
received via an end of an optical waveguide. The waveguide ends of
the input and output ports are optically connected across a switch
core. In this regard, for example, the input and output waveguide
ends can be physically located on opposite sides of a switch core
for direct or folded optical pathway communication therebetween, in
side-by-side matrices on the same physical side of a switch
interface facing a mirror, or they can be interspersed in a single
matrix arrangement facing a mirror.
[0005] Establishing a connection between an input port and a
selected output port, involves configuring an optical pathway
across the switch core between the input ports and the output
ports. One known way to configure the optical path is by moving or
bending optical fibers using, for example, piezoelectric actuators.
The actuators operate to displace the fiber ends so that signals
from the fibers are targeted at one another so as to form the
desired optical connection across the switch core. The amount of
movement is controlled based on the electrical signal applied to
the actuators. By appropriate arrangement of actuators,
two-dimensional targeting control can be effected.
[0006] Another way of configuring the optical path between an input
port and an output port involves the use of one or more moveable
mirrors interposed between the input and output ports. In this
case, the waveguide ends remain stationary and the mirrors are used
to deflect a light beam propagating through the switch core from
the input port to effect the desired switching.
Microelectromechanical devices with mirrors disposed thereon are
known in the art that can allow for two-dimensional targeting to
optically connect any input port to any output port. For example,
U.S. Pat. No. 5,914,801, entitled "Microelectromechanical Devices
Including Rotating Plates And Related Methods", which issued to
Dhuler et al. on Jun. 22, 1999; U.S. Pat. No. 6,087,747, entitled
"Microelectromechanical Beam For Allowing A Plate To Rotate In
Relation To A Frame In A Microelectromechanical Device", which
issued to Dhuler et al. on Jul. 11, 2000; and U.S. Pat. No.
6,134,042, entitled "Reflective MEMS Actuator With A Laser", which
issued to Dhuler et al. on Oct. 17, 2000, disclose
microelectromechanical systems (MEMS) having mirrors disposed
thereon that can be controllably moved in two dimensions to effect
optical switching.
[0007] U.S. Pat. No. 6,097,858, entitled "Sensing Configuration For
Fiber Optic Switch Control System", and U.S. Pat. No. 6,097,860,
entitled "Compact Optical Matrix Switch With Fixed Location
Fibers", both of which issued to Laor on Aug. 1, 2000, disclose
switch control systems for controlling the position of
two-dimensionally movable mirrors in an optical switch. The mirrors
can allow for two-dimensional targeting to optically connect any of
the input fibers to any of the output fibers.
[0008] An important consideration in optical switch design is
minimizing physical size for a given number of input and output
ports that are serviced, i.e., increasing the packing density of
ports and beam directing units. It has been recognized that greater
packing density can be achieved, particularly in the case of a
movable mirror-based beam directing unit, by folding the optical
path between the ports and the movable mirror and/or between the
movable mirror and the switch interface. Such a compact optical
matrix switch is disclosed in U.S. Pat. No. 6,097,860. In addition,
further compactness advantages are achieved therein by positioning
control signal sources outside of the fiber array and, preferably,
at positions within the folded optical path selected to reduce the
required size of the optics path.
[0009] Another example of a compact optical switch is disclosed by
Laor in WO 99/66354, entitled "Planar Array Optical Switch and
Method". The optical switch disclosed therein includes two arrays
of reflectors and a plurality of input and output fibers associated
with a respective reflector on one of the arrays. The optical
signal is directed along a "Z-shape" optical path from the input
fibers via the first array of reflector and the second array of
reflector to the output fibers.
[0010] However, the design of these prior art optical switches is
such that the optical components are arranged along the optical
path in a "Z-shape" pattern. A "Z-shape" arrangement of optical
components is not spatially efficient. Furthermore, the physical
size of an optical switch is determined by the number of input and
output ports. A plurality of input/output locations are provided so
that the input and output beams can enter/exit the switching core.
These input/output locations are commonly provided in the form of
rectangular or other arrays.
[0011] Referring to FIG. 1, a schematic presentation of a prior art
optical switch 100 having a Z-shaped arrangement of optical
components is shown. A light beam is launched into an input fiber
of input fiber bundle 116 and switched to a selected output fiber
of output fiber bundle 118 along a Z-shaped optical path through
switch 100, wherein micro-mirrors 110 on MEMS chips 112 are used to
fold the design. Such a folded optical pathway configuration allows
for a more compact switch design using a movable mirror based beam
directing unit. However, the general approach in prior art optical
switches is to individually collimate the beam from each input
fiber and to direct this beam to its dedicated mirror. This mirror
then deflects the beam to any one of the plurality of output
mirrors which then redirects the beam, i.e. compensates for the
angle, to its dedicated output fiber. As is seen from FIG. 1, this
design requires the use of a lens 114 for each individual input
fiber of input fiber bundle 116 and each individual output fiber of
output fiber bundle 118.
[0012] The Z-shape approach for switching an optical signal,
requires particular consideration with respect to the physical
spacing between the optical elements since the beam of light should
not be obstructed by any of the optical elements along the optical
path through the switch. It is apparent that this is not an
efficient design since physical size requirements are not optimized
in such an "off-axis" design.
[0013] The present invention provides an optical switch having an
"on-axis" design, and hence it can provide a more compact optical
switch than the prior art. In addition, arranging an
angle-to-offset (ATO) element between the deflection elements
provides for a re-imaging, and hence a small and low loss optical
switch can be provided in accordance with the invention.
[0014] Accordingly, it is an object of the invention to provide a
compact optical switch. It is a further object to provide a switch
with improved spatial efficiency in order to minimize a physical
size of the optical switch for a given number of input/output
ports.
[0015] It is yet a further object of the invention to provide an
optical switch having a common input/output region at the switching
core where the input/output light beams enter/exit the switching
core.
[0016] Another object of this invention is to provide a compact
optical cross-connect arrangement having a large number of
ports.
SUMMARY OF THE INVENTION
[0017] In accordance with the invention there is provided, an
optical switch comprising, at least one input port for launching a
beam of light into the optical switch, at least two output ports
for selectively receiving a beam of light, a switch core in optical
communication with the at least one input port and the at least two
output ports, at least a first optical bypass, disposed at the
switch core, comprising a first transmissive point through which
output beams pass out of the switch core, said output beams
substantially overlap each other at the first optical bypass, and a
plurality of beam deflectors disposed in the switch core for
switching the beam of light from the at least one input port to a
selected one of the at least two output ports through the
transmissive point of the at least first optical bypass.
[0018] In accordance with one embodiment of the invention, the at
least first optical bypass is in optical communication with the at
least one input port for allowing input beams to pass into the
switch core via the first transmissive point.
[0019] In a further embodiment of the present invention, at least
one of the plurality of beam deflectors is an independently
moveable beam deflector.
[0020] In yet another embodiment of the invention, the plurality of
beam deflectors includes a first plurality of independently
moveable beam deflectors, said first plurality of independently
moveable beam deflectors being disposed on a first surface
comprising the at least first optical bypass.
[0021] The optical switch in accordance with the invention further
includes at least a second optical bypass for allowing at least one
of input and output beams to pass into and out of the switch
core.
[0022] If desired, the plurality of beam deflectors includes a
second plurality of independently moveable beam deflectors, said
second plurality of independently moveable beam deflectors being
disposed on a second surface opposed to the first surface
comprising the at least second optical bypass.
[0023] In accordance with another embodiment of the invention, at
least one of the first and second surface is one of a planar and a
spherical surface.
[0024] Advantageously, the at least first optical bypass and the at
least second optical bypass are disposed along an axis of
symmetry.
[0025] In another embodiment of the present invention, the first
plurality of independently moveable beam deflectors is disposed
about the at least first optical bypass and the second plurality of
independently moveable beam deflectors is disposed about the at
least second optical bypass, said at least first optical bypass
being in optical communication with the at least one input port and
said at least second optical bypass being in optical communication
with the at least two output ports. If desired, the optical switch
further includes a first relay lens disposed about the axis of
symmetry between the at least one input port and the first
plurality of independently moveable beam deflectors, said first
relay lens for receiving a beam of light from the at least one
input port and for directing a beam of light to the first optical
bypass. Advantageously, the at least one input port and the first
plurality of independently moveable beam deflectors are disposed
near or at a focal plane of the first relay lens.
[0026] In accordance with a further embodiment of the present
invention, the optical switch further includes a second relay lens
disposed about the axis of symmetry between the second plurality of
independently moveable beam deflectors and the at least two output
ports, said second relay lens for receiving a beam of light from
the at least second optical bypass and for directing a beam of
light to a selected one of the at least two output ports.
Advantageously, the second plurality of independently moveable beam
deflectors and the at least two output ports are disposed near or
at a focal plane of the second relay lens.
[0027] If desired, a focal length of the first relay lens is
approximately equal to a focal length of the second relay lens.
[0028] In accordance with yet a further embodiment of the present
invention, the optical switch comprises an ATO element, said ATO
element being disposed between the first and the second plurality
of independently moveable beam deflectors along the axis of
symmetry, said axis of symmetry being an optical axis of the ATO
element. In accordance with an embodiment of the present invention,
the ATO element is for passing a beam of light three times
therethrough along an optical path between the at least one input
port and a selected one of the at least two output ports.
Advantageously, the first and the second plurality of independently
moveable beam deflectors are disposed near or at a focal plane of
the ATO element. If desired, the ATO element has a focal length
approximately equal to a near zone length or Rayleigh range of a
beam of light incident thereon.
[0029] In accordance with another embodiment of the invention, the
first plurality of independently moveable beam deflectors and the
second plurality of independently moveable beam deflectors comprise
an array of micro-mirrors. The array of micromirrors can be a
linear, rectangular, or radial array.
[0030] If desired, micro-lenses are disposed at the input and/or
output ports to operate as collimators.
[0031] The input and/or output ports can have a parallel
arrangement with respect to an axis of symmetry or they can be
radially disposed about the axis of symmetry.
[0032] In accordance with the invention, there is further provided
an optical switch comprising at least one input port for launching
a beam of light into the optical switch, at least two output ports
for selectively receiving the beam of light, a first plurality of
independently moveable deflectors disposed about a first optical
bypass for allowing a beam of light launched from the at least one
input port to pass therethrough, and wherein input beams passing
through the first optical bypass are substantially overlapping at
the first optical bypass, and a second plurality of independently
moveable deflectors disposed about a second optical bypass for
allowing a beam of light to pass therethrough to any one of the at
least two output ports, said second plurality of independently
moveable deflectors being disposed so as to receive a beam of light
that has passed through the first optical bypass, and wherein the
first and second plurality of independently moveable deflectors are
adapted to switch a beam of light, and wherein output beams passing
through the second optical bypass are substantially overlapping at
the second optical bypass.
[0033] In accordance with an embodiment of the invention, the first
and second optical bypasses comprise a transmissive point through
which input and output beams pass into and out of the optical
switch.
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] Exemplary embodiments of the invention will now be described
in conjunction with the drawings in which:
[0035] FIG. 1 is a schematic presentation of a prior art optical
switch having a Z-shaped arrangement of optical components;
[0036] FIG. 2 shows a schematic illustration of an optical switch
in accordance with an embodiment of the present invention;
[0037] FIG. 3 shows a schematic illustration of an optical switch
in accordance with a further embodiment of the present invention
having a radial arrangement of input and output ports;
[0038] FIG. 4 shows a schematic illustration of an optical switch
in accordance with a further embodiment of the present invention
further including relay lenses; and
[0039] FIG. 5 shows a schematic illustration of yet another
embodiment of an optical cross-connect in accordance with the
present invention further including an ATO element.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0040] The present invention provides an optical switch in which
light beams enter/exit a switch core through a common region where
the input/output beams intersect.
[0041] The optical switch in accordance with the present invention
allows for switching of optical signals between optical waveguides,
e.g. optical fibers. In an optical network, the fibers entering and
exiting a switching core may be bundled into a group of input
fibers and a group of output fibers. The ends of the input and
output fibers may further be arranged into two separate rectangular
arrays. If desired, the ends of the input and output fibers may be
mixed together in one rectangular array. However, in certain
applications, the input and output fibers may be arranged in other
suitable manners, as will be explained in further detail below,
particularly in conjunction with FIG. 2. Further, an individual
fiber may function as an input fiber as well as an output fiber
depending upon the direction of propagation of an optical signal in
a bidirectional communication environment. Accordingly, although
this description includes references to input and output fibers for
purposes of illustration, it will be understood that each of the
fibers may send and receive optical signals.
[0042] FIG. 2 shows a schematic illustration of an optical switch
200 in accordance with an embodiment of the present invention. As
can be seen from FIG. 2, the optical switch includes a switch core
210, an optical bypass 220, at least two deflectors (not shown)
within the switch core 210, an input waveguide 230a terminating in
a respective optical port 232a which incorporates a collimating
lens centered on the optical axis of the respective waveguide 230a,
and output waveguides 230b-d terminating in respective optical
ports 232b-d incorporating collimating lenses centered on the
optical axes of the respective waveguides 230b-d. The optical ports
232a-d are arranged radially about optical bypass 220 so that the
respective optical axes of the ports 232a-d converge at the optical
bypass 220.
[0043] The term optical bypass in this description is used to
provide an unobstructed path through the switch core to enable
light beams to enter/exit the switch core. This is accomplished by
providing an opening that defines a passage through which light
beams can pass. Alternatively, each optical bypass can be provided
as a region of the switch core structure that is substantially
transparent to optical wavelengths of light beams being switched
through optical switch. This latter arrangement can be readily
achieved by providing the switch core on a conventional Si and/or
SiO.sub.2 substrate, which is typically transparent to the
wavelengths of interest. In this case, the optical bypass is
readily constructed by providing a suitably sized region of the
substrate that is unobstructed by the deflectors and/or associated
deflector control circuitry.
[0044] The propagation path of a light beam is indicated by
arrowheads. An input beam is launched into optical port 232a. The
optical port 232a with its respective collimating lens guides the
input beam into the switch core 210 via bypass 220. The deflectors
provided within the switch core 210 operate to switch the light
beam to any of ports 232b-d. FIG. 2 shows an output beam exiting
the switch core 210 via bypass 220 to be switched to port 232d.
[0045] Turning now to FIG. 3, an optical switch 300 is presented in
accordance with a further embodiment of the present invention.
Switch 300 includes a switch core 310 defined by a pair of opposed
arrays 322a-b. Each array 322 includes mirrors/micro-mirrors 324
disposed on a MEMS and optical bypasses 320 through which light
beams can enter/exit the switch core 310.
[0046] Each MEMS mirror 324 is preferably provided as a
two-dimensionally tiltable micro-mirror which can be selectively
oriented, in a manner known in the art, to deflect a light beam
received from any optical element 320, 324 of the opposite array
322 to any other optical element 320, 324 of the opposite array
322. In this manner, each MEMS mirror 324 can be selectively
positioned to define an optical path between any two optical
elements 320, 324 of the opposite optical array 322. This
positioning capability of each MEMS mirror 324 enables highly
versatile switching of light beams within the switch core 310. If
desired, the MEMS mirrors can be arranged on any surface, such as a
sphere, rather than on a plane.
[0047] As shown in FIG. 3, optical bypass 320a is associated with
an input fiber bundle 312 that includes waveguides 314a-d
terminating in optical ports 316a-d which incorporate a collimating
lens centered on the optical axes of the respective waveguides
314a-d, and optical bypass 320b is associated with an output fiber
bundle 332 that includes waveguides 334a-d terminating in optical
ports 336a-d which incorporate a collimating lens centered on the
optical axes of the respective waveguides 334a-d.
[0048] Advantageously, as is seen from FIG. 3, the optical
components of switch 300 are provided about an axis of symmetry 325
passing through optical bypasses 320. The optical paths of light
beams entering/exiting switch core 310 are converging at a
transmissive point 318 as they pass through a respective optical
bypass 320 into and out of the switch core 310. In the embodiment
presented in FIG. 3, this is achieved by radially arranging
waveguides 314 and 334 about a respective optical bypass 320, so
that the respective optical axes of ports 316 and 336 converge at a
respective optical bypass 320.
[0049] A mirror 324 of one array 322 can be positioned to define a
propagation path between any two optical elements 324, 320 of the
respective opposite array 322. In the present invention, this
capability is employed to provide a folded path 3D switch core 310
in which the mirrors 324 of the optical arrays 322 can be
positioned to switch incoming light beams into multiple switching
optical paths.
[0050] In general, a switching optical path is a propagation path
in which a light beam received (by a respective mirror 324) from a
bypass 320 is deflected to a respective mirror 324 of the opposite
array 322, or vice versa. Thus in a switching optical path, a light
beam traverses the switch core 310 with two reflections.
[0051] To illustrate the operation of switch 300, an input beam IB
is shown to enter switch 300 from the left via bypass 320a. Input
beam IB is deflected at point A by mirror 324 on array 322b. Mirror
324 deflects the input beam IB towards point B on mirror 324 of the
opposed array 322a, and from there it is guided out of switch core
310 via bypass 320b towards output port 336a to result a switched
output beam SOB1, as indicated by a dash-dot line. Alternatively, a
different output port can be targeted. In this case, mirror 324 on
array 322b deflects the input beam IB from point A to point C where
another mirror 324 on array 322a deflects the beam out of switch
core 310 via bypass 320b towards output port 336d to result a
switched output beam SOB2, as indicated by a dashed line.
[0052] It is appreciated that many more optical pathways can be
selected between any of the input waveguides 314 and output
waveguides 334. Furthermore, as is known in the art, light beams
may propagate bi-directionally within each waveguide 314, 334.
Similarly, each fiber bundle 312, 332 may carry bi-directional
traffic, with beams propagating in one direction in some
waveguides, and in the opposite direction in other waveguides of
the same fiber bundle. It is further seen that due to the symmetry
of the optical arrays 322 defining the switch core 310, light beams
may enter the switch core 310 through any fiber bundle 312, 322,
and may exit the switch core 310 through any other fiber bundle
312, 322.
[0053] Referring to FIG. 4, an optical switch 400 is presented in
accordance with a further embodiment of the present invention.
Switch 400 includes an input fiber bundle 412, an output fiber
bundle 432, a switch core 410, an input relay lens 450a, an output
relay lens 450b. The input fiber bundle 412 includes a plurality of
waveguides 414a-d terminating in micro-lenses 416a-d centered on
the optical axis of the respective waveguides 414a-d. Analogously,
output fiber bundle 432 includes a plurality of waveguides 434a-d
terminating in micro-lenses 436a-d centered on the optical axis of
the respective waveguides 434a-d. The fiber bundles 412, 432 are
arranged on opposite sides of the switch core 410 along an optical
axis OA passing through relay lenses 450a, b. The switch core 410
is defined by a pair of opposed arrays 422a-b. Each array 422a,b
includes mirrors/micro-mirrors 424 disposed on a MEMS chip and
optical bypasses 420a,b comprising a transmissive point 418a, b
through which light beams can enter/exit the switch core 410.
[0054] Each MEMS array 422 is provided with an optical bypass 420,
such as a hole or optically transparent region, as described
heretofore, through which light beams propagating to/from
waveguides 414, 434 can enter/exit the switch core 410 through the
transmissive point 418. The optical paths of the light beams
emerging from waveguides 414, 434 are made to converge within this
transmissive point at the optical bypass. In the embodiment
presented in FIG. 4, this is achieved by means of relay lenses
450a, b disposed between fiber bundle 412, 432 and the nearest MEMS
array 422a, b along the optical axis OA passing through relay
lenses 450a, b. The fiber bundle 412 and the MEMS array 422a are
separated from the relay lens 450a by a distance that corresponds
approximately to a focal length f.sub.1 of relay lens 450a. Fiber
bundle 432 and the MEMS array 422b are separated from the relay
lens 450b by a distance that corresponds approximately to a focal
length f.sub.2 of relay lens 450b. Advantageously, relay lenses
450a, b are chosen to have a same focal length. This arrangement
facilitates a compact switch core design while enabling a light
beam to propagate between each waveguide 414, 434 and a respective
MEMS mirror 424 on the opposite side of the switch core 410.
[0055] Advantageously, the embodiment of the invention presented in
FIG. 4 provides an optical switch 400 that is easier to package
than optical switch 300 presented in FIG. 3, for example, because
the waveguides 414, 434 of fiber bundles 412, 432 are symmetrically
arranged about a respective axis of symmetry that substantially
coincides with the optical axis OA. However, more optical
components, i.e. the relay lenses 450a, 450b, are required to
realize this embodiment. In the illustrated embodiment, each fiber
bundle 412, 432 comprises 4 waveguides 414a-d, 434a-d arranged in a
linear array (that is, lying in the plane of the page). It will be
appreciated that each fiber bundle 412, 432 may comprise fewer or
more waveguides 414, 434, and that the waveguides 414, 434 may be
arranged in a two-dimensional array, that is, with each waveguide
414, 434 terminating in a plane extending substantially
perpendicular to the page of the drawings. Within each fiber bundle
412, 432, each waveguide 414, 434 terminates in a respective
optical port 416, 436 which incorporates a micro-lens centered on
the optical axis of the respective waveguide 414, 434. The optical
ports 416, 436 operate to guide a light beam propagating into the
switch core 410 from the waveguides 414, 434 and vice versa.
[0056] Generally optical switch 400 operates analogously to switch
300 presented in conjunction with FIG. 3, i.e. with the exception
of converging the input/output beams in a transmissive point at the
optical bypass of the switch core by using a relay lens. An
exemplary input beam IB enters switch core 410 via bypass 420a. The
input beam IB is deflected at point A by one of the micro-mirrors
424 of MEMS array 422b. From there, two possible pathways are shown
in FIG. 4 to result in a switched output beam SOB1 (dash-dot line)
by deflecting the beam via point B and a switched output beam SOB2
(dashed line) by deflecting the beam via point C. In dependence
upon a tilt of mirror 424 of array 422b at point A the input beam
is deflected to another micro-mirror 424 of the opposite array 422a
at point B in one switching mode. Mirror 424 at point B directs the
beam out of the switch core 410 via transmissive point 418b at
optical bypass 420b to point D at the relay lens 450b. In another
switching mode, mirror 424 of array 422b at point A deflects the
input beam to another mirror 424 of the opposite array 422a at
point C Mirror 424 at point C is operated to deflect the beam out
of the switch core 410 via transmissive point 418b at the optical
bypass 420b to point E at the relay lens 450b. Both output beams,
SOB1 and SOB2, are directed to their respective output ports 436a,
436d by means of relay lens 450b.
[0057] FIG. 5 shows yet another embodiment of an optical
cross-connect 500 in accordance with the present invention. As is
shown in FIG. 5, the optical cross-connect 500 includes a switch
core 510 defined by a pair of opposed optical arrays 522a, b
symmetrically arranged on opposite sides of an angle-to-offset
(ATO) element 560, such as an ATO lens 560 having a focal length
f.sub.ATO. The ATO lens 560 operates to deflect the propagation
path of light beams within the switch core 510. For the purposes of
the present invention, an ATO lens 560 can be provided as any
suitable optical element having optical power, e.g. a mirror or a
lens.
[0058] While not essential for the purpose of the present
invention, the ATO element preferably has a focal length f.sub.ATO
that substantially corresponds to the near zone length (multi mode)
or the Rayleigh range (single mode) of a beam of light propagating
through optical cross-connect 500. The use of such an ATO element
means that the size, i.e. the cross-sectional area, of a beam
switched through switch core 510 is substantially the same on both
mirror arrays 522a, b. If the beam size is the same on both mirror
arrays 522a, b as a result of providing an ATO lens 560 having a
focal length substantially equal to the Rayleigh range, a very
compact optical switch can be designed. In addition, the provision
of re-imaging optics (relay lenses 550a, b and ATO lens 560),
enables to achieve a low loss optical switch.
[0059] The ATO principle is described in further detail in Canadian
Patent Application No. 2,326,362, the disclosure of which is herein
incorporated by reference.
[0060] Optical switch 500 is scalable to 4000.times.4000 switch
based on arrays 522 of two-dimensional tilt mirrors 524 and ATO
lens 560.
[0061] Each array 522a, b includes micro-mirrors 524 disposed on a
MEMS chip and transmissive points 518a, b at respective optical
bypasses 520a, b through which light beams can enter/exit the
switch core 510. In accordance with the embodiment presented in
FIG. 5, optical bypasses 520a, b are provided in the form of an
optically transparent region, for example a region on the MEMS
substrate that is unobstructed by a micro-mirror, associated mirror
control circuitry or any other optical element or a window. The
optical arrays 522a, b are preferably positioned to lie in
respective opposite focal planes of the ATO lens 560. As is seen
from FIG. 5, each optical array 522 has an axis of symmetry that
substantially coincides with an optical axis of the ATO lens 560
and the optical axis OA of switch 500.
[0062] Each MEMS mirror 524 is preferably provided as a
two-dimensionally tiltable micro-mirror which can be selectively
oriented, as described heretofore, to deflect a light beam received
from any optical element 520, 524 of the opposite array 522 to any
other optical element 520, 524 of the opposite array 522. In this
manner, each MEMS mirror 524 is selectively positioned to define an
optical path between any two optical elements 520, 524 of the
opposite optical array 522.
[0063] Optical switch 500 further comprises an input fiber bundle
512 including a plurality of waveguides 514a having an input
micro-lens array 516a placed at an end face of input fiber bundle
512 with one micro-lens centered on an optical axis of each fiber.
An input relay lens 550a is provided between the micro-lens array
516a and a first array 522a that includes the two-dimensional tilt
mirrors/micro mirrors 524. The input microlens array 516a and the
first array 522a are separated from the input relay lens 550a by a
distance that corresponds approximately to the focal length f.sub.1
of the input relay lens 550a. This input relay lens 550a directs a
beam of light incident thereon through a transmissive point 518a at
bypass 520a of the first array 522a. The first array 522a is
followed by an ATO lens 560, and a second array 522b having an
array of two-dimensional tilt mirrors/micro mirrors 524 and a
bypass 520b comprising a transmissive point 518b disposed thereon.
Both, the first array 522a and the second array 522b are arranged
at a distance from the ATO lens 560 which corresponds approximately
to the focal length f.sub.ATO of ATO lens 560. The second array
522b is followed by an output relay lens 550b which focuses the
light beams to an output micro-lens array 516b provided at an end
face of an output fiber bundle 514b having one micro-lens centered
on an optical axis of each fiber. The second array 522b and the
output micro-lens array 516b are separated from the output relay
lens 550b by a distance that corresponds approximately to the focal
length f.sub.2 of the output relay lens 550b. In accordance with a
preferred embodiment of the present invention, the input relay lens
550a and the output relay lens 550b have a same focal length,
f.sub.1=f.sub.2, for maintaining a high degree of symmetry and
compactness of optical cross-connect 500.
[0064] All optical components of cross-connect 500 are arranged
about the optical axis OA. Such an arrangement provides for an even
more compact design of an optical switch in accordance with the
present invention, and lessens aberration effects of the lens.
[0065] In order to demonstrate more clearly how optical
cross-connect 500 functions, an exemplary input beam of light IB is
traced along an optical path A to H through cross-connect 500. The
input beam IB exits input fiber bundle 512a at point A, i.e. from
an end face of fiber 514a having a micro-lens disposed thereon.
Beam IB propagates parallel to the optical axis OA until it reaches
point B on the input relay lens 550a. Input relay lens 550a directs
beam IB at an angle to the optical axis OA to point C on the ATO
lens 560 through the transmissive point 518a at the bypass 520a in
the first array 522a. The ATO lens 560 directs the beam parallel to
the optical axis OA to point D on one of the micro-mirrors 524 on
the second array 522b. From this point on, i.e. point D, there are
two possible pathways shown in FIG. 5 for the beam to yield a
switched output beam SOB1, as indicated by a dash-dot line, or a
switched output beam SOB2, as indicated by the dashed line, in
dependence upon a tilting of the respective micro-mirror 524.
However, for illustrative purposes only the propagation path
following the dash-dot line is described hereinafter.
[0066] The respective micro-mirror 524 on the second array 522b
switches the light beam to point E on one of the micro-mirrors on
the first array 522a after passing through the ATO lens 560. The
respective micro-mirror 524 on the first array 522a directs the
light beam back to point F on the ATO lens 560 parallel to the
optical axis OA and then at an angle to the optical axis OA to
point G on the output relay lens 550b through transmissive point
518b at bypass 520b of the second array 522b. The output relay lens
550b collects the beam of light beam coming from bypass 520b and
images it on the output micro-lens array 516b at point H. An output
fiber 514b of the output fiber bundle 512b collects the beam from
the output micro-lens array 516b to yield SOB2.
[0067] It is appreciated that cross-connect 500 also functions in
reverse, i.e. the output fiber bundle 512b then functions as the
input fiber bundle and so forth.
[0068] Advantageously, this embodiment of an optical cross-connect
500 in accordance with the present invention provides for the use
of high fill factor arrays of two-dimensionally tiltable
micro-mirrors 524 to redirect light beams while providing a very
compact switch core 510 which lessens aberration effects of the ATO
lens 560. The linear arrangement of all components along the
optical axis OA affords a very compact design of cross-connect 500.
A further factor in affording a compact cross-connect 500 is that
small optical components can be used in this switch because of the
beam geometry.
[0069] Numerous other embodiments can be envisaged without
departing from the spirit and scope of the invention. For example,
multiple optical bypasses can be provided on any one MEMS array. In
this case, a plurality of symmetry axes exist that are parallel to
the optical axis OA.
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