CA2359554A1 - Microelectromechanical optical switches including optical paths having optical loss equalization therebetween - Google Patents
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Abstract
Embodiments of the present invention can provide optical switches that include first and second reflectors in first and second optical devices that are optically coupled to define a first optical path between the first and second reflectors. The first optical path includes a plurality of first freespace portions having complementary optical losses associated therewith to provide a first optical loss. Third and fourth reflectors are optically coupled to define a second optical path between the third and fourth reflectors that includes a plurality of second freespace portions having complementary optical losses associated therewith to provide a second optical loss that is equalized with the first optical loss. In some embodiments, the third and fourth reflectors are in the first and second optical devices respectively. In other embodiments, the third and fourth reflectors are in third and fourth devices.
Description
Doc. No: CRO-52 CA Patent MICROELECTROMECHANICAL OPTICAL SWITCHES INCLUDING OPTICAL PATHS HAVING
OPTICAL LOSS EQUALIZATION THERI:BETWEEN
Field of the Invention The present invention relates to the field of microelectromechanical devices, and more particularly, to microelectromechanical optical switches.
B~ck~round of the Invention Microelectromechanical systems and devices (MEMS) have been recently developed as alternatives for conventional electromechanical devices, in-part, because MEMS
devices are potentially low-cost, due to the use of simplified microelectronic fabrication techniques. New functionality may also be provided because MEMS devices can be much smaller than conventional electromechanical systems and devices.
In the area of optical switching, MEMS technology has been used to fabricate optical switches using MEMS reflectors to switch inputs thereto to selected switch outputs. As the number of inputs and outputs of optical switches increase, significant optical losses may be introduced to optical radiation switched by the MEM optical switch.
In particular, the optical loss may increase with the distance that the optical radiation travels. For example, as shown in Figure 1, first and second optical paths 101, 102 through a 2 x 2 MEMS optical switch 100 can have path lengths 2A and 2B respectively, where A is greater than B. Optical radiation that propagates along the first optical path 101 may be attenuated more than optical radiation that propagates along the second optical path 102.
Accordingly, as the number of inputs and outputs increase so may the losses because the distances that the optical radiation propagates can be greater.
If the attenuation associated with an optical path becomes significant, additional components, such as attenuators, may be used to compensate for the loss.
However, it may be difficult to determine which outputs of a switch may need attenuation because the optical path used to switch the optical radiation from an input to the output may be different depending, for example, on which input is being switched to the output. It may, therefore, be advantageous to Doc. No: CRO-52 CA Patent add attenuators to all outputs of the MEMS optical switch. Unfortunately, adding the attenuators may further increase costs associated with the MEMS optical switch. In view of the above, there continues to be a need for improved optical switches.
Summary of the Invention Embodiments of the present invention can provide optical switches that include first and second reflectors in first and second optical devices that are optically coupled to define a first optical path between the first and second reflectors. The first optical path includes a plurality of first freespace portions having complementary optical losses associated therewith to provide a first optical loss.
Third and fourth reflectors are optically coupled to define a second optical path between the third and fourth reflectors that includes a plurality of second freespace portions having complementary optical losses associated therewith to provide av second optical loss that is equalized with the first optical loss. In some embodiments, the third and fourth reflectors are in the first and second optical devices respectively. In other embodiments, the third and fourth reflectors are in third and fourth devices.
In some embodiments, the plurality of first freespace portions and the plurality of second freespace portions comprise about equal lengths. In other embodiments, the first optical path intersects a plurality of first reflective surfaces and the second optical path intersects a plurality of second reflective surfaces, wherein the plurality of first reflective surfaces is equal to the plurality of second reflective surfaces.
In other embodiments, the first optical path intersects a first reflective surface that reflects the first optical radiation and the second optical path intersects a second reflective surface that reflects the second optical radiation, wherein the first and second reflective surfaces are selected to equalize the second optical radiation loss with the first optical radiation loss.
In other embodiments, the first optical path includes a plurality of first optical devices and the second optical path includes a plurality of second optical devices. In some embodiments, the plurality of first and second optical devices are coupled by optical fiber. In still other embodiments, the optical devices are on separate dies.
Doc. No: CRO-52 CA Patent Embodiments according to the present invention can also include a first MEMS
optical device on a first die that has a first input thereto and first N+1 outputs therefrom and a second MEMS optical device on a second die that has a second input thereto and second N+1 outputs therefrom. The second input is aligned with one of the first N-~-1 outputs, wherein the first and second MEMS optical devices function as a 1 x 2N+1 MEMS optical switch.
In some embodiments, the first and second MEMS optical devices comprise first and second MEMS optical demultiplexer devices coupled in series.. In other embodiments, the first input is located on a first side of the first MEMS optical device and one of the N+1 outputs is on a second side of the first MEMS optical device that is opposite the first side.
Embodiments according to the present invention can also include a first MEMS
optical device on a first die that has first N+1 inputs thereto and an output therefrom and a second MEMS optical device on a second die that as an input thereto and N+1 outputs therefrom. The first output is aligned with the input of the second MEMS optical device, wherein the first and second MEMS optical devices can function as a N+1 x N+1 MEMS optical switch.
In some embodiments, the first MEMS optical device comprises a MEMS optical multiplexer and the second MEMS optical device comprises a MEMS optical demultiplexer coupled in series. In other embodiments, one the N+1 inputs is located on a first side of the first MEMS optical device and the output of the first MEMS optical device is on a second side that is apposite the first side.
Brief Description of the Dr~wiin~s_ Figure 1 is a plan view of a conventional MEMS optical switch.
Figure 2 is block diagram that illustrates embodiments of MEMS optical switches according to the present invention.
Figure 3 is block diagram that illustrates embodiments of optical switches according to the present invention.
Figure 4 is a plan view that illustrates embodiments of freespace portions of optical paths according to the present invention.
Figure 5 is block diagram that illustrates embodiments of optical switches shown in Figure 3.
OPTICAL LOSS EQUALIZATION THERI:BETWEEN
Field of the Invention The present invention relates to the field of microelectromechanical devices, and more particularly, to microelectromechanical optical switches.
B~ck~round of the Invention Microelectromechanical systems and devices (MEMS) have been recently developed as alternatives for conventional electromechanical devices, in-part, because MEMS
devices are potentially low-cost, due to the use of simplified microelectronic fabrication techniques. New functionality may also be provided because MEMS devices can be much smaller than conventional electromechanical systems and devices.
In the area of optical switching, MEMS technology has been used to fabricate optical switches using MEMS reflectors to switch inputs thereto to selected switch outputs. As the number of inputs and outputs of optical switches increase, significant optical losses may be introduced to optical radiation switched by the MEM optical switch.
In particular, the optical loss may increase with the distance that the optical radiation travels. For example, as shown in Figure 1, first and second optical paths 101, 102 through a 2 x 2 MEMS optical switch 100 can have path lengths 2A and 2B respectively, where A is greater than B. Optical radiation that propagates along the first optical path 101 may be attenuated more than optical radiation that propagates along the second optical path 102.
Accordingly, as the number of inputs and outputs increase so may the losses because the distances that the optical radiation propagates can be greater.
If the attenuation associated with an optical path becomes significant, additional components, such as attenuators, may be used to compensate for the loss.
However, it may be difficult to determine which outputs of a switch may need attenuation because the optical path used to switch the optical radiation from an input to the output may be different depending, for example, on which input is being switched to the output. It may, therefore, be advantageous to Doc. No: CRO-52 CA Patent add attenuators to all outputs of the MEMS optical switch. Unfortunately, adding the attenuators may further increase costs associated with the MEMS optical switch. In view of the above, there continues to be a need for improved optical switches.
Summary of the Invention Embodiments of the present invention can provide optical switches that include first and second reflectors in first and second optical devices that are optically coupled to define a first optical path between the first and second reflectors. The first optical path includes a plurality of first freespace portions having complementary optical losses associated therewith to provide a first optical loss.
Third and fourth reflectors are optically coupled to define a second optical path between the third and fourth reflectors that includes a plurality of second freespace portions having complementary optical losses associated therewith to provide av second optical loss that is equalized with the first optical loss. In some embodiments, the third and fourth reflectors are in the first and second optical devices respectively. In other embodiments, the third and fourth reflectors are in third and fourth devices.
In some embodiments, the plurality of first freespace portions and the plurality of second freespace portions comprise about equal lengths. In other embodiments, the first optical path intersects a plurality of first reflective surfaces and the second optical path intersects a plurality of second reflective surfaces, wherein the plurality of first reflective surfaces is equal to the plurality of second reflective surfaces.
In other embodiments, the first optical path intersects a first reflective surface that reflects the first optical radiation and the second optical path intersects a second reflective surface that reflects the second optical radiation, wherein the first and second reflective surfaces are selected to equalize the second optical radiation loss with the first optical radiation loss.
In other embodiments, the first optical path includes a plurality of first optical devices and the second optical path includes a plurality of second optical devices. In some embodiments, the plurality of first and second optical devices are coupled by optical fiber. In still other embodiments, the optical devices are on separate dies.
Doc. No: CRO-52 CA Patent Embodiments according to the present invention can also include a first MEMS
optical device on a first die that has a first input thereto and first N+1 outputs therefrom and a second MEMS optical device on a second die that has a second input thereto and second N+1 outputs therefrom. The second input is aligned with one of the first N-~-1 outputs, wherein the first and second MEMS optical devices function as a 1 x 2N+1 MEMS optical switch.
In some embodiments, the first and second MEMS optical devices comprise first and second MEMS optical demultiplexer devices coupled in series.. In other embodiments, the first input is located on a first side of the first MEMS optical device and one of the N+1 outputs is on a second side of the first MEMS optical device that is opposite the first side.
Embodiments according to the present invention can also include a first MEMS
optical device on a first die that has first N+1 inputs thereto and an output therefrom and a second MEMS optical device on a second die that as an input thereto and N+1 outputs therefrom. The first output is aligned with the input of the second MEMS optical device, wherein the first and second MEMS optical devices can function as a N+1 x N+1 MEMS optical switch.
In some embodiments, the first MEMS optical device comprises a MEMS optical multiplexer and the second MEMS optical device comprises a MEMS optical demultiplexer coupled in series. In other embodiments, one the N+1 inputs is located on a first side of the first MEMS optical device and the output of the first MEMS optical device is on a second side that is apposite the first side.
Brief Description of the Dr~wiin~s_ Figure 1 is a plan view of a conventional MEMS optical switch.
Figure 2 is block diagram that illustrates embodiments of MEMS optical switches according to the present invention.
Figure 3 is block diagram that illustrates embodiments of optical switches according to the present invention.
Figure 4 is a plan view that illustrates embodiments of freespace portions of optical paths according to the present invention.
Figure 5 is block diagram that illustrates embodiments of optical switches shown in Figure 3.
Doc. No: CRO-52 CA Patent Figure 6 is a perspective view that illustrates embodiments of 2 x 2 optical switches according to the present invention.
Figure 7 is a perspective view that illustrates embodiments of 4 x 4 optical switches according to the present invention.
Figure 8 is a block diagram that illustrates embodimenla of 1 x (MxN+1) optical switches according to the present invention.
Figure 9 is a block diagram that illustrates embodiments of optical routers switches according to the present invention.
Detailed Description of the Invention The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, the size of regions and elements therein may be exaggerated for clarity. Like numbers refer to like elements throughout.
It will be understood that when an element such as a layer, region, substrate or reflector is referred to as being "on" another element, it can be directly on the other element or intervening elements may also be present. It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, v~hen an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intervening elements present. Elements can also be "optically coupled" using, for example, optical fiber, waveguides, freespace, etc. wherein there may be intervening elements.
As used herein, the term "optical radiation" can include radiation that can be used to transmit data in a communications system, such as radiation in the visible, ultraviolet, infrared and/or other portions of the electromagnetic radiation spectrum.
As used herein, the term "switch" can include optical devices that function as multiplexers, demultiplexers, and switches. The term multiplexer can include, for example, Doc. No: CRO-52 CA Patent optical devices that can provide any input applied thereto to an output of the multiplexer. The term demultiplexer can include, for example, optical devices that can provide an input applied thereto to any output of the demultiplexer.
As used herein, the term "equalized" can include reductions in differences between losses, attenuations, and/or distances associated with different optical paths through optical switches. Accordingly, it will be understood that "equalized" is not limited to optical paths that have equal losses, attenuations, and/or distances. The loss or attenuation may be due to the propagation of the optical radiation in freespace (such as air or other gases), waveguides, or other optical conductors. Optical loss and attenuation can also result: from the reflection of optical radiation from reflectors in optical switches.
As used herein, the term "complementary" can include a plurality of separate portions of unequal lengths or amounts which can be combined to provide a total length or amount. For example, as described herein, complementary lengths of freespace portions of an optical path can be combined to provide a total length which is equalized with the total lengths of other optical paths.
According to embodiments of the present invention, freespace portions of optical paths through an optical switch can be configured to equalize optical losses associated with different optical paths. In particular, the length of freespace portions of the optical paths can be equalized to reduce differences in optical attenuation between optical paths.
Accordingly, the need for additional components, such as attenuators or amplifiers, may be reduced.
Figure 2 is a block diagram that illustrates embodiments of MEMS optical switches 200 according to the present invention. According to Figure 2, the MEMS optical switch 200 has N
(I1...IN) inputs and N (01...ON) outputs (N x N). Optical radiation can be provided from any of the N inputs to any of the N outputs by propagating the optical radiation along one of NZ
optical paths through the MEMS optical switch 200 as indicated by the dashed lines and node 204.
Each of the N2 optical paths can have an optical loss associated therewith. In general, the longer the optical path, the greater the optical loss andlor attenuation associated with the optical path. For example, if first optical radiation propagates for a first length along a first optical path having an optical loss and a second optical radiation propagates along the optical path for a second length that is greater than the first length, the second optical radiation may be more Doc. No: CRO-52 CA Patent attenuated than the first optical radiation. According to the present invention, the N2 optical paths can be configured to equalize the optical losses associated therewith so that the attenuation of optical radiation from any input to any output of the switch c:an be equalized.
Figure 3 is a block diagram that illustrates embodiments of optical switches according to the present invention. According to Figure 3, a 3 x 3 optical switch 300 can include first through third demultiplexer devices 305,310,315 coupled to first through third multiplexer devices 320,325,330.
Inputs Il-I3 are coupled to the first through third demu tiplexer devices 305,310,315 respectively. Outputs O1-03 are coupled to the first through third multiplexer devices 320,325,330 respectively. The first through third demultiplexer devices 305,310,315 are coupled to the first through third multiplexer devices 320,325,330 via optical fibers 301a-i. Other types of coupling may be used.
Optical radiation is switched from the inputs Il-I3 to the outputs 01-03 by configuring the demultiplexer and multiplexer devices to conduct the optical radiation along desired optical paths. For example, optical radiation can be provided from the input I1 to the output 03 by configuring the first demultiplexer device 305 and the third mu.ltiplexer device 330 to conduct optical radiation along an optical path from the input I1 to the optical fiber 301a to the output 03.
Each optical path can include one or more freespace portions in the demultiplexer/multiplexer devices. For example, an optical pavth from input Il to output 01 includes a first freespace portion in the demultiplexer device 305 and a second freespace portion in the multiplexer device 320. The freespace portion in each device can include the distance that optical radiation travels from an optical fiber at the input to the device to a reflector to another optical fiber at an output of the device.
Each of the freespace portions can have an optical loss associated therewith.
The optical loss or attenuation for each freespac;e pouion can be related to the length of that portion.
Moreover, the optical loss for each freespace portion in a device can be an accumulation of losses including losses from the transition from optical fiber to freespace at the input to the device, the propagation of the optical radiation in freespace (such as air or other gases), the reflection of the optical radiation from a reflector positioned along the optical path, and a transition back to an optical fiber at the output of the device. Losses may also be caused by Doc. No: CRO-52 CA Patent propagation in optical fiber that couples the devices together. lElowever, it will be understood that the losses in the optical fibers can be small compared to losses in the free-space portions.
Figure 4 is a plan view that illustrates embodiments of reflectors in a demultiplexer device 400 according to the present invention. As shown in Figure 4, optical radiation incident at an input 401 can propagate over three different freespace portions of respective optical paths in the demultiplexer device 400 depending on which reflector i s in a reflecting position.
Moreover, the optical loss associated with optical radiation output by the demultiplexer device 400 can also depend on the optical path followed.
As shown in Figure 4, the optical radiation can propagate a "short" length freespace portion A along optical path 420 from the input 401 to the first reflector 405 to the output 421.
Optical radiation propagates a "medium" length freespace portiion B along optical path 425 from the input 405 to the second reflector 410 to the second output 422. Optical radiation propagates a "long" length freespace portion C along optical path 430 from the input 405 to the third reflector 415 to the third output 423, where C > B > A. Accordingly, the optical loss associated with optical path 420 can be less than that associated with optical path 425 which can be less than the optical loss associated with optical path 430. It will be understood that the terms short, medium, and long are used above to convey the relative lengths of the freespace portions A, B, and C.
Figure S is a plan view that illustrates a detailed view of a portion of the 3 x 3 optical switch shown in Figure 3. According to Figure 5, the freespace portions of optical paths 301c, 301d, 301h are configured to equalize the optical losses associated with the optical paths used to provide optical radiation from the inputs I1-I3 to the output 03. In particular, optical radiation that propagates from any of the inputs Il-I3 to output 03 can gravel along a freespace portion of the optical path configured to equalize the loss associated with that freespace portion with that of the other freespace portions of the other optical paths used to provide other inputs to the same or other outputs. In some embodiments, the freespace portions of the optical paths can be equalized by pairing together complementary length freespace portions from separate devices as part of an optical path.
For example, as shown in Figure 5, the freespace portion of optical path 301c includes the distance from the input Il to thc: reflector 530 to the output 570 in demultiplexer device 305 (a short length portion) and the distance from the input 571 to the reflector 545 to the output 03 Doc. No: CRO-52 CA Patent of multiplexes device 320 (a long length portion). Accordingly, the short and long length freespace portions in the devices 305 and 320 are complementary to one another to provide an optical path having an associated optical loss that is about equal to optical losses associated with other optical paths that couple any of the inputs Il-I3 to any of the outputs Ol-03.
Moreover, the freespace portion of optical path 341d can be equalized with the freespace portion of optical path 301c (described above) by pairing complementary freespace portions of devices 310 and 320 with one another. For example, a first freespace portion of the optical path 301d includes the distance from the input I2 to the reflector 535 to the output 574 of demultiplexer device 310 (a long portion) and the distance from the input 573 to the reflector 560 to the output 03 of multiplexes device 320 (a short portion). Accordingly, the optical paths 341c-d can each include a short and a long freespace portion to equalize the loss associated with the respective optical paths 301c-d.
The freespace portion of optical path 301h can be equalized with the freespace portions of optical paths 301c and 301d by paring complementary frees~pace portions of the devices 315 and 320. For example, a first freespace portion of optical path 301h includes the distance from the input I3 to the reflector 540 to the output 515 in the demultiplexer device 315 (a medium length portion) and the distance from the input 572 to the reflecaor 550 to the output 03 of the multiplexes device 320 (a medium length portion). A combined length of two medium length portions can be about equal to a combined length of a short length and a long length portion.
Accordingly, the loss associated with the optical path 301h can. be equalized with the losses associated with the optical paths 301b-c. Therefore, optical radiation switched from any input to output 03 can have equalized optical losses.
The optical radiation can be reflected from the input to the selected optical path by positioning the reflectors in reflecting or non-reflecting positions. As used herein, the term "reflecting position" includes positions where a reflective surface of the reflector intersects optical radiation applied to an input so that the optical radiation is reflected by the reflector. The term "non-reflecting" position includes positions where the reflective surface does not intersect the optical path so that optical radiation conducted along the optical path is not reflected by the reflector.
Reflectors according to the present invention can be formed using wet etching or other techniques known to those having skill in the art. The fabrication of moveable reflectors is Doc. No: CRO-52 CA Patent further described, for example, in commonly assigned U.S. Patent Application Serial No.
09/542,672, April 4, 2000, entitled Add-Drop Optical Switches Including Parallel Fixed and Moveable Reflectors and Methods of Operating Same, the entirety of which is incorporated herein by reference.
In some embodiments, the reflectors can be moved to the reflecting and non-reflecting positions by actuators such as those disclosed in commonly assigned U.S.
Patent 5,909,078 to Wood et al. (Wood) entitled Thermal Arched Beam Microelectromechanical Actuators, the entire disclosure of which is incorporated herein by reference. Wood discloses a family of thermal arched beam microelectromechanical actuators that in<;lude an arched beam which extends between spaced-apart supports on a microelectronic substrate. The arched beam expands upon application of heat thereto. For example, as described in Wood, a current is passed through the arched beams to cause thermal expansion thereof. Alternatively, as described in Wood, the thermal arched beams are heated by an external heavter across an air gap.
In other embodiments, the reflectors can be moved magnetically. For example, the reflectors may be moved between the reflecting and non-reflecting positions by applying a magnetic field to the reflector. Magnetically actuated reflectors are described further, for example, in commonly assigned U.S. Patent Application Serial No. 09/487,976 entitled MEMS
Magnetically Actuated Switch and Associated Switching Arrays, the entire disclosure of which is incorporated herein by reference.
The actuators can be mechanical actuators such as those described in commonly assigned U.S. Patent Application Serial No. 09/542,170 entitled MicroElectroMechanical Optical Cross-Connect Switches Including Mechanical Actuators and MethoGds Of Operation Same, the entire disclosure of which is incorporated herein by reference. Other types of actuators can be used.
Figure 6 is a perspective view that illustrates 2 x 2 optical switches according to the present invention in a stacked arrangement having multiple levels of multiplexes and demultiplexer devices 605,610,615,620. According to Figure ~6, freespace portions of optical paths 625a-d are equalized by pairing complementary freespace portions of the optical paths in devices on different levels with one another. For example, a long length freespace portion of the optical path 625b in demultiplexer device 60S on a first level is paired with a short length freespace portion of the optical path 625b in the demultiplexer device 615 on a second level. A
long length freespace portion of the optical path 625d in the de:multiplexer device 610 on the Doc. No: CRO-52 CA Patent second level is paired with a short length freespace portion of the optical path 625d in the demultiplexer device 615 on the second level. Accordingly, the optical losses associated with the freespace portions of the optical paths 625b,d can be equalized by pairing complementary length freespace portions in separate devices on different level,>. Other stacked arrangements having multiple levels may be used..
Figure 7 is a perspective view that illustrates 4 x 4 optical switches according to the present invention in a stacked arrangement having 4 levels of rnultiplexer and demultiplexer devices. The optical losses associated with the freespace portions of optical paths 701-716 can be equalized by pairing together complementary length freespace portions in separate demultiplexer and multiplexer devices 720a-h on different levels as illustrated in Figure 7.
Other stacked arrangements having multiple levels may be used.
Figure 8 is a block diagram that illustrates embodiments of 1 x (MxN)+1 optical demultiplexer devices according to the present invention. As shown in Figure 8, each 1 x (N+1) demultiplexer device can provide N outputs oriented orthogonal to the input and an N+lth output that is parallel to the input. The input and the N+lth output can be located on opposite sides of the demultiplexer device.
A 1 x (MxN)+1 demultiplexer device 800 can be provided by coupling M 1 x (N+1) demultiplexer devices together. In particular, an N+lth output of a first 1 x (N+1) demultiplexer device 805 can be coupled to an input of a second 1 x (N+1) demultiplexer device 810. The second 1 x (N+1) demultiplexer device 810 can provide a 2N+:lth output which can be coupled to an input of a third 1 x (N+1) demultiplexer device 815. The third 1 x (N+1) demultiplexer device 815 can provide 3N+1 outputs. Accordingly, a 1 x (MxhT)+1 demultiplexer can be provided by coupling M 1 x (N+1) demultiplexer devices together. It will be understood that more or fewer demultiplexer devices may be used.
Moreover, the N+lth outputs of the demultiplexer devices can be coupled to inputs of other demultiplexer devices via freespace. Accordingly, a 1 x (MxN)+1 demultiplexer device according to the present invention may reduce the need for optical fiber to couple outputs to inputs of the demultiplexer devices.
Figure 9 is a block diagram that illustrates embodiments of optical muter devices according to the present invention. As shown in Figure 9, an (1V+1) x 1 multiplexer device 905 can provide an input stage for a series of M 1 x N+1 demultiple.xers. In particular, an output of Doc. No: CRO-52 CA Patent the 1 x (N+1) multiplexer device 905 is coupled to an input of a first 1 x N+1 demultiplexer device 910. An N+lth output of the demultiplexer device 910 is coupled to an input of a second 1 x N+1 demultiplexer device 915. More or fewer demultiplexer devices may be used.
Moreover, the N+lth outputs of the demultiplexer devices 710,715 can be coupled to associated inputs via freespace. Accordingly, an optical muter device according to the present invention may reduce the need for optical fibers to couple outputs to inputs of the switch devices used therein.
In the drawings and specification, there have been disclosed typical preferred embodiments of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention being set forth in the following claims.
Figure 7 is a perspective view that illustrates embodiments of 4 x 4 optical switches according to the present invention.
Figure 8 is a block diagram that illustrates embodimenla of 1 x (MxN+1) optical switches according to the present invention.
Figure 9 is a block diagram that illustrates embodiments of optical routers switches according to the present invention.
Detailed Description of the Invention The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, the size of regions and elements therein may be exaggerated for clarity. Like numbers refer to like elements throughout.
It will be understood that when an element such as a layer, region, substrate or reflector is referred to as being "on" another element, it can be directly on the other element or intervening elements may also be present. It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, v~hen an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intervening elements present. Elements can also be "optically coupled" using, for example, optical fiber, waveguides, freespace, etc. wherein there may be intervening elements.
As used herein, the term "optical radiation" can include radiation that can be used to transmit data in a communications system, such as radiation in the visible, ultraviolet, infrared and/or other portions of the electromagnetic radiation spectrum.
As used herein, the term "switch" can include optical devices that function as multiplexers, demultiplexers, and switches. The term multiplexer can include, for example, Doc. No: CRO-52 CA Patent optical devices that can provide any input applied thereto to an output of the multiplexer. The term demultiplexer can include, for example, optical devices that can provide an input applied thereto to any output of the demultiplexer.
As used herein, the term "equalized" can include reductions in differences between losses, attenuations, and/or distances associated with different optical paths through optical switches. Accordingly, it will be understood that "equalized" is not limited to optical paths that have equal losses, attenuations, and/or distances. The loss or attenuation may be due to the propagation of the optical radiation in freespace (such as air or other gases), waveguides, or other optical conductors. Optical loss and attenuation can also result: from the reflection of optical radiation from reflectors in optical switches.
As used herein, the term "complementary" can include a plurality of separate portions of unequal lengths or amounts which can be combined to provide a total length or amount. For example, as described herein, complementary lengths of freespace portions of an optical path can be combined to provide a total length which is equalized with the total lengths of other optical paths.
According to embodiments of the present invention, freespace portions of optical paths through an optical switch can be configured to equalize optical losses associated with different optical paths. In particular, the length of freespace portions of the optical paths can be equalized to reduce differences in optical attenuation between optical paths.
Accordingly, the need for additional components, such as attenuators or amplifiers, may be reduced.
Figure 2 is a block diagram that illustrates embodiments of MEMS optical switches 200 according to the present invention. According to Figure 2, the MEMS optical switch 200 has N
(I1...IN) inputs and N (01...ON) outputs (N x N). Optical radiation can be provided from any of the N inputs to any of the N outputs by propagating the optical radiation along one of NZ
optical paths through the MEMS optical switch 200 as indicated by the dashed lines and node 204.
Each of the N2 optical paths can have an optical loss associated therewith. In general, the longer the optical path, the greater the optical loss andlor attenuation associated with the optical path. For example, if first optical radiation propagates for a first length along a first optical path having an optical loss and a second optical radiation propagates along the optical path for a second length that is greater than the first length, the second optical radiation may be more Doc. No: CRO-52 CA Patent attenuated than the first optical radiation. According to the present invention, the N2 optical paths can be configured to equalize the optical losses associated therewith so that the attenuation of optical radiation from any input to any output of the switch c:an be equalized.
Figure 3 is a block diagram that illustrates embodiments of optical switches according to the present invention. According to Figure 3, a 3 x 3 optical switch 300 can include first through third demultiplexer devices 305,310,315 coupled to first through third multiplexer devices 320,325,330.
Inputs Il-I3 are coupled to the first through third demu tiplexer devices 305,310,315 respectively. Outputs O1-03 are coupled to the first through third multiplexer devices 320,325,330 respectively. The first through third demultiplexer devices 305,310,315 are coupled to the first through third multiplexer devices 320,325,330 via optical fibers 301a-i. Other types of coupling may be used.
Optical radiation is switched from the inputs Il-I3 to the outputs 01-03 by configuring the demultiplexer and multiplexer devices to conduct the optical radiation along desired optical paths. For example, optical radiation can be provided from the input I1 to the output 03 by configuring the first demultiplexer device 305 and the third mu.ltiplexer device 330 to conduct optical radiation along an optical path from the input I1 to the optical fiber 301a to the output 03.
Each optical path can include one or more freespace portions in the demultiplexer/multiplexer devices. For example, an optical pavth from input Il to output 01 includes a first freespace portion in the demultiplexer device 305 and a second freespace portion in the multiplexer device 320. The freespace portion in each device can include the distance that optical radiation travels from an optical fiber at the input to the device to a reflector to another optical fiber at an output of the device.
Each of the freespace portions can have an optical loss associated therewith.
The optical loss or attenuation for each freespac;e pouion can be related to the length of that portion.
Moreover, the optical loss for each freespace portion in a device can be an accumulation of losses including losses from the transition from optical fiber to freespace at the input to the device, the propagation of the optical radiation in freespace (such as air or other gases), the reflection of the optical radiation from a reflector positioned along the optical path, and a transition back to an optical fiber at the output of the device. Losses may also be caused by Doc. No: CRO-52 CA Patent propagation in optical fiber that couples the devices together. lElowever, it will be understood that the losses in the optical fibers can be small compared to losses in the free-space portions.
Figure 4 is a plan view that illustrates embodiments of reflectors in a demultiplexer device 400 according to the present invention. As shown in Figure 4, optical radiation incident at an input 401 can propagate over three different freespace portions of respective optical paths in the demultiplexer device 400 depending on which reflector i s in a reflecting position.
Moreover, the optical loss associated with optical radiation output by the demultiplexer device 400 can also depend on the optical path followed.
As shown in Figure 4, the optical radiation can propagate a "short" length freespace portion A along optical path 420 from the input 401 to the first reflector 405 to the output 421.
Optical radiation propagates a "medium" length freespace portiion B along optical path 425 from the input 405 to the second reflector 410 to the second output 422. Optical radiation propagates a "long" length freespace portion C along optical path 430 from the input 405 to the third reflector 415 to the third output 423, where C > B > A. Accordingly, the optical loss associated with optical path 420 can be less than that associated with optical path 425 which can be less than the optical loss associated with optical path 430. It will be understood that the terms short, medium, and long are used above to convey the relative lengths of the freespace portions A, B, and C.
Figure S is a plan view that illustrates a detailed view of a portion of the 3 x 3 optical switch shown in Figure 3. According to Figure 5, the freespace portions of optical paths 301c, 301d, 301h are configured to equalize the optical losses associated with the optical paths used to provide optical radiation from the inputs I1-I3 to the output 03. In particular, optical radiation that propagates from any of the inputs Il-I3 to output 03 can gravel along a freespace portion of the optical path configured to equalize the loss associated with that freespace portion with that of the other freespace portions of the other optical paths used to provide other inputs to the same or other outputs. In some embodiments, the freespace portions of the optical paths can be equalized by pairing together complementary length freespace portions from separate devices as part of an optical path.
For example, as shown in Figure 5, the freespace portion of optical path 301c includes the distance from the input Il to thc: reflector 530 to the output 570 in demultiplexer device 305 (a short length portion) and the distance from the input 571 to the reflector 545 to the output 03 Doc. No: CRO-52 CA Patent of multiplexes device 320 (a long length portion). Accordingly, the short and long length freespace portions in the devices 305 and 320 are complementary to one another to provide an optical path having an associated optical loss that is about equal to optical losses associated with other optical paths that couple any of the inputs Il-I3 to any of the outputs Ol-03.
Moreover, the freespace portion of optical path 341d can be equalized with the freespace portion of optical path 301c (described above) by pairing complementary freespace portions of devices 310 and 320 with one another. For example, a first freespace portion of the optical path 301d includes the distance from the input I2 to the reflector 535 to the output 574 of demultiplexer device 310 (a long portion) and the distance from the input 573 to the reflector 560 to the output 03 of multiplexes device 320 (a short portion). Accordingly, the optical paths 341c-d can each include a short and a long freespace portion to equalize the loss associated with the respective optical paths 301c-d.
The freespace portion of optical path 301h can be equalized with the freespace portions of optical paths 301c and 301d by paring complementary frees~pace portions of the devices 315 and 320. For example, a first freespace portion of optical path 301h includes the distance from the input I3 to the reflector 540 to the output 515 in the demultiplexer device 315 (a medium length portion) and the distance from the input 572 to the reflecaor 550 to the output 03 of the multiplexes device 320 (a medium length portion). A combined length of two medium length portions can be about equal to a combined length of a short length and a long length portion.
Accordingly, the loss associated with the optical path 301h can. be equalized with the losses associated with the optical paths 301b-c. Therefore, optical radiation switched from any input to output 03 can have equalized optical losses.
The optical radiation can be reflected from the input to the selected optical path by positioning the reflectors in reflecting or non-reflecting positions. As used herein, the term "reflecting position" includes positions where a reflective surface of the reflector intersects optical radiation applied to an input so that the optical radiation is reflected by the reflector. The term "non-reflecting" position includes positions where the reflective surface does not intersect the optical path so that optical radiation conducted along the optical path is not reflected by the reflector.
Reflectors according to the present invention can be formed using wet etching or other techniques known to those having skill in the art. The fabrication of moveable reflectors is Doc. No: CRO-52 CA Patent further described, for example, in commonly assigned U.S. Patent Application Serial No.
09/542,672, April 4, 2000, entitled Add-Drop Optical Switches Including Parallel Fixed and Moveable Reflectors and Methods of Operating Same, the entirety of which is incorporated herein by reference.
In some embodiments, the reflectors can be moved to the reflecting and non-reflecting positions by actuators such as those disclosed in commonly assigned U.S.
Patent 5,909,078 to Wood et al. (Wood) entitled Thermal Arched Beam Microelectromechanical Actuators, the entire disclosure of which is incorporated herein by reference. Wood discloses a family of thermal arched beam microelectromechanical actuators that in<;lude an arched beam which extends between spaced-apart supports on a microelectronic substrate. The arched beam expands upon application of heat thereto. For example, as described in Wood, a current is passed through the arched beams to cause thermal expansion thereof. Alternatively, as described in Wood, the thermal arched beams are heated by an external heavter across an air gap.
In other embodiments, the reflectors can be moved magnetically. For example, the reflectors may be moved between the reflecting and non-reflecting positions by applying a magnetic field to the reflector. Magnetically actuated reflectors are described further, for example, in commonly assigned U.S. Patent Application Serial No. 09/487,976 entitled MEMS
Magnetically Actuated Switch and Associated Switching Arrays, the entire disclosure of which is incorporated herein by reference.
The actuators can be mechanical actuators such as those described in commonly assigned U.S. Patent Application Serial No. 09/542,170 entitled MicroElectroMechanical Optical Cross-Connect Switches Including Mechanical Actuators and MethoGds Of Operation Same, the entire disclosure of which is incorporated herein by reference. Other types of actuators can be used.
Figure 6 is a perspective view that illustrates 2 x 2 optical switches according to the present invention in a stacked arrangement having multiple levels of multiplexes and demultiplexer devices 605,610,615,620. According to Figure ~6, freespace portions of optical paths 625a-d are equalized by pairing complementary freespace portions of the optical paths in devices on different levels with one another. For example, a long length freespace portion of the optical path 625b in demultiplexer device 60S on a first level is paired with a short length freespace portion of the optical path 625b in the demultiplexer device 615 on a second level. A
long length freespace portion of the optical path 625d in the de:multiplexer device 610 on the Doc. No: CRO-52 CA Patent second level is paired with a short length freespace portion of the optical path 625d in the demultiplexer device 615 on the second level. Accordingly, the optical losses associated with the freespace portions of the optical paths 625b,d can be equalized by pairing complementary length freespace portions in separate devices on different level,>. Other stacked arrangements having multiple levels may be used..
Figure 7 is a perspective view that illustrates 4 x 4 optical switches according to the present invention in a stacked arrangement having 4 levels of rnultiplexer and demultiplexer devices. The optical losses associated with the freespace portions of optical paths 701-716 can be equalized by pairing together complementary length freespace portions in separate demultiplexer and multiplexer devices 720a-h on different levels as illustrated in Figure 7.
Other stacked arrangements having multiple levels may be used.
Figure 8 is a block diagram that illustrates embodiments of 1 x (MxN)+1 optical demultiplexer devices according to the present invention. As shown in Figure 8, each 1 x (N+1) demultiplexer device can provide N outputs oriented orthogonal to the input and an N+lth output that is parallel to the input. The input and the N+lth output can be located on opposite sides of the demultiplexer device.
A 1 x (MxN)+1 demultiplexer device 800 can be provided by coupling M 1 x (N+1) demultiplexer devices together. In particular, an N+lth output of a first 1 x (N+1) demultiplexer device 805 can be coupled to an input of a second 1 x (N+1) demultiplexer device 810. The second 1 x (N+1) demultiplexer device 810 can provide a 2N+:lth output which can be coupled to an input of a third 1 x (N+1) demultiplexer device 815. The third 1 x (N+1) demultiplexer device 815 can provide 3N+1 outputs. Accordingly, a 1 x (MxhT)+1 demultiplexer can be provided by coupling M 1 x (N+1) demultiplexer devices together. It will be understood that more or fewer demultiplexer devices may be used.
Moreover, the N+lth outputs of the demultiplexer devices can be coupled to inputs of other demultiplexer devices via freespace. Accordingly, a 1 x (MxN)+1 demultiplexer device according to the present invention may reduce the need for optical fiber to couple outputs to inputs of the demultiplexer devices.
Figure 9 is a block diagram that illustrates embodiments of optical muter devices according to the present invention. As shown in Figure 9, an (1V+1) x 1 multiplexer device 905 can provide an input stage for a series of M 1 x N+1 demultiple.xers. In particular, an output of Doc. No: CRO-52 CA Patent the 1 x (N+1) multiplexer device 905 is coupled to an input of a first 1 x N+1 demultiplexer device 910. An N+lth output of the demultiplexer device 910 is coupled to an input of a second 1 x N+1 demultiplexer device 915. More or fewer demultiplexer devices may be used.
Moreover, the N+lth outputs of the demultiplexer devices 710,715 can be coupled to associated inputs via freespace. Accordingly, an optical muter device according to the present invention may reduce the need for optical fibers to couple outputs to inputs of the switch devices used therein.
In the drawings and specification, there have been disclosed typical preferred embodiments of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention being set forth in the following claims.
Claims (19)
1. An optical switch comprising:
first and second reflectors in first and second optical devices that are optically coupled to define a first optical path between the first and second reflectors that includes a plurality of first freespace portions having complementary optical losses associated therewith to provide a first optical loss; and third and fourth reflectors that are optically coupled to define a second optical path between the third and fourth reflectors that includes a plurality of second freespace portions having complementary optical losses associated therewith to provide a second optical loss that is equalized with the first optical loss.
first and second reflectors in first and second optical devices that are optically coupled to define a first optical path between the first and second reflectors that includes a plurality of first freespace portions having complementary optical losses associated therewith to provide a first optical loss; and third and fourth reflectors that are optically coupled to define a second optical path between the third and fourth reflectors that includes a plurality of second freespace portions having complementary optical losses associated therewith to provide a second optical loss that is equalized with the first optical loss.
2. An optical switch according to Claim 1, wherein the third and fourth reflectors are in the first and second optical devices respectively.
3. An optical switch according to Claim 1 further comprising:
third and fourth optical devices wherein the third and fourth reflectors are in third and fourth devices.
third and fourth optical devices wherein the third and fourth reflectors are in third and fourth devices.
4. An optical switch according to Claim 1, wherein the plurality of first freespace portions and the plurality of second freespace portions comprise about equal lengths.
5. An optical switch according to Claim 1, wherein the first optical path intersects a plurality of first reflective surfaces and the second optical path intersects a plurality of second reflective surfaces, wherein the plurality of first reflective surfaces is equal in number to the plurality of second reflective surfaces.
6. An optical switch according to Claim 1, wherein the first optical path intersects a first reflective surface that reflects the first optical radiation and the second optical path intersects a second reflective surface that reflects the second optical radiation, wherein the first and second reflective surfaces are selected to equalize the second optical radiation loss with the first optical radiation loss.
7. An optical switch according to Claim 1, wherein the first optical path includes a plurality of first optical devices and the second optical path includes a plurality of second optical devices.
8. An optical switch according to Claim 7, wherein the plurality of first optical devices are coupled by optical fiber.
9. An optical switch according to Claim 1, wherein the first and second optical devices are on separate dies.
10. An optical switch according to Claim 1, wherein the pluralities of first and second freespace portions comprise air.
11. An optical switch according to Claim 1, wherein the first and second optical devices are on first and second levels of the optical switch respectively.
12. An optical switch according to Claim 1, wherein the first optical device comprises a multiplexer and the second optical device comprises a demultiplexer.
13. An optical switch according to Claim 1, wherein the first and second optical devices comprise first and second MEMS optical devices.
14. A MEMS optical switch comprising:
a first MEMS optical device on a first die having a first input thereto and first N+1 outputs therefrom; and a second MEMS optical device on a second die having a second input thereto and second N+1 outputs therefrom, the second input is aligned with one of the first N+1 outputs, wherein the first and second MEMS optical devices function as a 1 x 2N+1 MEMS optical switch.
a first MEMS optical device on a first die having a first input thereto and first N+1 outputs therefrom; and a second MEMS optical device on a second die having a second input thereto and second N+1 outputs therefrom, the second input is aligned with one of the first N+1 outputs, wherein the first and second MEMS optical devices function as a 1 x 2N+1 MEMS optical switch.
15. A MEMS optical switch according to Claim 14, wherein the first and second MEMS
optical devices comprise first and second MEMS optical demultiplexer devices coupled in series.
optical devices comprise first and second MEMS optical demultiplexer devices coupled in series.
16. A MEMS optical switch according to Claim 14, wherein the first input is located on a first side of the first MEMS optical device and one of the N+1 outputs is on a second side of the first MEMS optical device that is opposite the first side.
17. A MEMS optical switch comprising:
a first MEMS optical device on a first die having first N+1 inputs thereto and an output therefrom; and a second MEMS optical device on a second die having an input thereto and N+1 outputs therefrom, the first output is aligned with the input of the second MEMS
optical device, wherein the first and second MEMS optical devices can function as a N+1 x N+1 MEMS
optical switch.
a first MEMS optical device on a first die having first N+1 inputs thereto and an output therefrom; and a second MEMS optical device on a second die having an input thereto and N+1 outputs therefrom, the first output is aligned with the input of the second MEMS
optical device, wherein the first and second MEMS optical devices can function as a N+1 x N+1 MEMS
optical switch.
18. A MEMS optical switch according to Claim 17, wherein the first MEMS
optical device comprises a MEMS optical multiplexer and the second MEMS optical device comprises a MEMS optical demultiplexer coupled in series.
optical device comprises a MEMS optical multiplexer and the second MEMS optical device comprises a MEMS optical demultiplexer coupled in series.
19. A MEMS optical switch according to Claim 17, wherein one of the N+1 inputs is located on a first side of the first MEMS optical device and the output of the first MEMS optical device is on a second side that is opposite the first side.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US70639900A | 2000-11-03 | 2000-11-03 | |
| US09/706,399 | 2000-11-03 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2359554A1 true CA2359554A1 (en) | 2002-05-03 |
Family
ID=24837383
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2359554 Abandoned CA2359554A1 (en) | 2000-11-03 | 2001-10-22 | Microelectromechanical optical switches including optical paths having optical loss equalization therebetween |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2359554A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107907992A (en) * | 2017-12-01 | 2018-04-13 | 西安交通大学 | The fast steering mirror actuation mechanism and start method of direct stress electromagnetic drive |
-
2001
- 2001-10-22 CA CA 2359554 patent/CA2359554A1/en not_active Abandoned
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107907992A (en) * | 2017-12-01 | 2018-04-13 | 西安交通大学 | The fast steering mirror actuation mechanism and start method of direct stress electromagnetic drive |
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