Optical waveguides – With optical coupler – Switch
Reexamination Certificate
2002-11-19
2004-10-26
Ullah, Akm Enayet (Department: 2874)
Optical waveguides
With optical coupler
Switch
C359S199200
Reexamination Certificate
active
06810166
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to optical communication equipment and, more specifically, to micro-electromechanical system (MEMS) devices for use in such equipment.
2. Description of the Related Art
Optical communication systems often employ optical waveguide devices that use optical waveguides to confine and direct light and to process optical signals. A representative waveguide device may be an optical cross-connect, a router, a modulator, etc. Waveguide devices often include 1×N optical switches, one species of which is a 1×2 switch. A 1×2 switch receives a single input and directs it to one of two outputs.
A 1×2 waveguide switch may be implemented using a Mach-Zehnder interferometer. In such a switch, an optical signal can be directed to one of two output ports by changing the relative phase shift (&phgr;) in two interferometer arms. For example, when &phgr;=0, signals from the two arms interfere constructively at the first output port and destructively at the second output port. Similarly, when &phgr;=&pgr;, the signals interfere constructively at the second output port and destructively at the first output port. Therefore, changing the phase shift from 0 to &pgr; causes the switch to redirect an input optical signal from one output port to the other. The phase shift is typically controlled thermally, e.g., by elevating the temperature of one arm with respect to the other arm. A temperature change induces an index of refraction change, which produces a phase shift.
One problem with a thermo-optic Mach-Zehnder switch is that, because of the required heating/cooling of interferometer arms, switching speed may be relatively low. Another problem is that thermal actuation entails power consumption, which might become substantial in devices having a relatively large number of switches. In addition, thermo-optic Mach-Zehnder switches require careful temperature control, e.g., to reduce thermal drift, which affects signal extinction at the “off” output port and may result in inter-port crosstalk.
SUMMARY OF THE INVENTION
The problems in the prior art are addressed in accordance with the principles of the invention by a MEMS switch. A switch of the invention includes a movable cantilevered beam that has a bumper portion and a waveguide corresponding to one port of the switch. The beam is designed for in-plane motion and can be deflected, e.g., using a three-electrode motion actuator having one electrode on each side of the beam, which itself acts as the third electrode. The beam moves toward a side electrode in response to a voltage difference applied between the beam and that electrode. The beam has two terminal positions, each defined by a stopper. At each terminal position, the bumper portion of the beam is pushed against a corresponding stopper, which aligns the waveguide in the beam with one of two stationary waveguides, each corresponding to a port of the switch. The MEMS switch can be configured to operate as a 1×2 switch with light from a single input port being routed to one of two output ports, or as a 2×1 switch with light from one of two input ports being routed to a single output port. A switch of the invention may be fabricated using a single silicon-on-insulator (SOI) wafer.
According to one embodiment, the invention is a MEMS device, comprising: (A) a stationary part having at least first and second waveguides and at least a first electrode; and (B) a movable cantilevered beam attached at one end to the stationary part, wherein: the shape of the beam defines a third waveguide; and the beam is adapted to bend in response to a voltage difference selectively applied between the beam and the first electrode to align the third waveguide with either the first waveguide or the second waveguide.
According to another embodiment, the invention is a method of operating a MEMS device having at least first, second, and third waveguides, the method comprising selectively applying a voltage difference between a movable cantilevered beam and a first electrode of the MEMS device to align the third waveguide with either the first waveguide or the second waveguide, wherein the MEMS device comprises: a stationary part having at least the first and second waveguides and at least the first electrode; and the movable cantilevered beam attached at one end to the stationary part, wherein: the shape of the beam defines the third waveguide; and the beam bends when the voltage difference is applied between the beam and the first electrode.
According to yet another embodiment, the invention is a method of fabricating a MEMS device, comprising: forming a stationary part having at least first and second waveguides and at least a first electrode; and forming a movable cantilevered beam attached at one end to the stationary part, wherein: the shape of the beam defines a third waveguide; and the beam is adapted to bend in response to a voltage difference selectively applied between the beam and the first electrode to align the third waveguide with either the first waveguide or the second waveguide.
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patent: 6600849 (2003-07-01), Ducellier et al.
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patent: 2002/0171121 (2002-11-01), Ozgur
patent: 2004/0097066 (2004-05-01), Ozgur
“Planar Microoptomechanical Waveguide Switches” by Thor Bakke et al., IEEE Journal on Selected Topics in Quantum Electronics, vol. 8, No. 1, Jan./Feb. 2002, pp. 64-72.
Baumann Frieder H.
Stuart Howard R.
Lucent Technologies - Inc.
Ullah Akm Enayet
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