Optical waveguides – With optical coupler – Switch
Reexamination Certificate
2000-11-22
2003-09-09
Nguyen, Khiem (Department: 2839)
Optical waveguides
With optical coupler
Switch
C385S119000
Reexamination Certificate
active
06618518
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to microelectromechanical system (MEMS) devices and operating methods therefor, and more particularly to MEMS optical cross-connect (OXC) switches and methods of operating same.
BACKGROUND OF THE INVENTION
Microelectromechanical systems (MEMS) recently have been developed as alternatives for conventional electromechanical devices, such as relays, actuators, valves and sensors. MEMS devices are potentially low-cost devices, due to the use of simplified microelectronic fabrication techniques. New functionality also may be provided because MEMS devices can be physically much smaller than conventional electromechanical devices.
MEMS technology has been used to fabricate optical cross-connect (OXC) switches that include a plurality of input optical paths, a plurality of output optical paths, and an array of electromechanical optical switches, such as movable reflectors, that selectively move to couple the plurality of input optical paths to the plurality of output optical paths. In particular, MEMS optical cross-connect switches can include an array of n rows and m columns of reflectors on a substrate such as a microelectronic substrate, to reflect optical energy from any of m input optical paths to any of n output optical paths. The selected reflector can be located in the array where the column associated with the m inputs and the row associated with the n outputs intersect. The selected reflector can be placed in a reflecting position to reflect the optical energy from the input to the selected output. The other reflectors can be placed in a non-reflecting position, so as not to impede the propagation of the optical energy from the input to the selected reflector and to the output.
Some conventional MEMS OXC switches operate by orienting the reflectors of the array using magnetic fields. In particular, the reflectors therein may be oriented horizontally (in the plane of the substrate on which the reflectors are located) in a non-reflecting position, and vertically (orthogonal to the substrate) in a reflecting position. Therefore, to switch optical energy from an input of the OXC switch to an output thereof, the selected reflector can be oriented vertically, and other blocking reflectors can be oriented horizontally. Magnetically actuated MEMS OXC switches are described, for example, in U.S. patent application Ser. No. 09/489,264, filed Jan. 21, 2000 (now U.S. Pat. No. 6,396,975), entitled
MEMS Optical Cross-Connect Switch
, to Wood et al., and assigned to the assignee of the present invention, the disclosure of which is hereby incorporated herein by reference in its entirety, and U.S. patent application Ser. No. 09/487,976, filed Jan. 20, 2000 (now U.S. Pat. N
0
. 6,366,186), entitled
MEMS Magnetically Actuated Switches and Associated Switching Arrays
to Hill et al., assigned to the assignee of the present invention, the disclosure of which is hereby incorporated herein by reference in its entirety.
Magnetically actuated optical cross-connect switches also are disclosed in three publications by members of the Berkeley Sensor and Actuator Center (BSAC) of the University of California, Berkeley. In particular, in a publication entitled
Magnetic Microactuation of Torsional Polysilicon Structures
to Judy et al., Sensors and Actuators A, Vol. 53, 1996, pp. 392-397, a microactuator technology utilizing magnetic thin films and polysilicon flexures is applied to torsional microstructures. These structures are constructed in a batch-fabrication process that combines electroplating with conventional IC-lithography, materials, and equipment. A microactuated mirror made from a 430 &mgr;m×130 &mgr;m×15 &mgr;m nickel-iron plate attached to a pair of 400 &mgr;m×2.2 &mgr;m×2.2 &mgr;m polysilicon torsional beams may be rotated more than 90° out of the plane of the wafer and actuated with torque greater than 3.0 nN m. The torsional flexure structure constrains motion to rotation about a single axis, which can be an advantage for a number of microphotonic applications (e.g., beam chopping, scanning and steering). See the abstract of this publication.
A 1997 publication entitled
Magnetically Actuated, Addressable Microstructures
to Judy et al., Journal of Microelectromechanical Systems, Vol. 6, No. 3, September 1997, pp. 249-255, discloses that surface-micromachined, batch-fabricated structures that combine plated-nickel films with polysilicon mechanical flexures to produce individually addressable, magnetically activated devices have been fabricated and tested. Individual microactuator control was achieved in two ways: 1) by actuating devices using the magnetic field generated by coils integrated around each device and 2) by usingo electrostatic forces to clamp selected devices to all insulated ground plane while unclamped devices are freely moved through large out-of-plane excursions by an off-chip magnetic field. The disclosed application for these structures is micromirrors for microphotonic systems where they can be used either for selection from an array of mirrors or else individually for switching among fiber paths. See the abstract of this publication. Moreover, this publication discloses, at Page 253, four advantages of using electrostatic forces (instead of using integrated coils), to achieve individual microactuator control. These advantages include the following:
1) Arrays of elements can be readily addressed using well-known digital-memory address techniques.
2) The clamping scheme is easily incorporated in a batch-fabrication process.
3) Clamping is accomplished with very little increase in the area of an array in contrast to that needed for on-chip coils.
4) Although power is required to generate the magnetic field necessary to move unclamped devices, no static power is needed to clamp devices. An array of devices that could be clamped in the up position as well as the down position, would only need power to generate the magnetic field necessary to change the up-down configuration of the matrix.
Finally, a 1998 publication entitled
Magnetically Actuated Micromirrors for Fiber-Optic Switching
to Behin et al., Solid-State Sensor and Actuator Workshop, Hilton Head Island, S.C., Jun. 8-11, 1998, pp. 273-276, describes the design, fabrication and operation of magnetically actuated micromirrors with electrostatic clamping in dual positions for fiber-optic switching applications. The mirrors are actuated by an off-chip electromagnet and can be individually addressed by electrostatic clamping either to the substrate surface or to the vertically etched sidewalls formed on a top-mounted (110)-silicon chip. This publication shows the positioning accuracy inherent in this approach makes it suitable for N×M optical switches. See the abstract of this publication.
Other actuation techniques may be used to orient the reflectors of the array. For example, application Ser. No. 09/542,170, filed Apr. 5, 2000 (now U.S. Pat. No. 6,445,842), entitled
Microelectromechanical Optical Cross-Connect Switches Including Mechanical Actuators and Methods of Operating Same
to Dhuler et al., and assigned to the assignee of the present invention, the disclosure of which is hereby incorporated herein by reference in its entirety, discloses MEMS OXC switches having mechanical actuators. In particular, the MEMS OXC switches can include a plurality of reflectors, wherein each of the plurality of the reflectors is movable to at least one of a respective first reflector position along a respective optical beam path from an associated input of the MEMS OXC switch to an associated output thereof and a respective second reflector position outside the optical beam path. A mechanical actuator moves to at least one of a first mechanical actuator position and a second mechanical actuator position. A selector selects ones of the plurality of reflectors to be coupled to the mechanical actuator and at least one of the plurality of reflectors to be decoupled from the mechanical actuator, wherein the mechanical actuator is coupled to the
Agrawal Vivek
Mahadevan Ramaswamy
JDS Uniphase Corporation
Myers Bigel & Sibley & Sajovec
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