MEMS interferometer-based reconfigurable optical add-and-drop multiplexor

• US 7,068,372 B1
• Filed: 01/28/2003
• Issued: 06/27/2006
• Est. Priority Date: 01/28/2003
• Status: Active Grant

• Current Assignee: Silicon Light Machines Corporation (SCREEN Holdings Co., Ltd.)
• Original Assignee: Silicon Light Machines Corporation (SCREEN Holdings Co., Ltd.)
• Inventors: Carlisle, Clinton B., Trisnadi, Jahja I.
• Primary Examiner(s): LEE, HWA S
• Application Number:
  US10/353,694
• Time in Patent Office: 1,246 Days
• Field of Search: 356/450, 356/491
• US Class Current: 356/450
• CPC Class Codes: G02B 26/001 based on interference in an adjustable optical cavity interference filters G02B5/28; devices or arrangements using multiple reflections in spectrometry or monochromators G01J3/26
• CPC Class Codes: G02B 6/29311 Diffractive element operating in transmission
• CPC Class Codes: G02B 6/29349 Michelson or Michelson/Gires-Tournois configuration, i.e. based on splitting and interferometrically combining relatively delayed signals at a single beamsplitter
• CPC Class Codes: G02B 6/29361 Interference filters, e.g. multilayer coatings, thin film filters, dichroic splitters or mirrors based on multilayers, WDM filters
• CPC Class Codes: G02B 6/2938 for multiplexing or demultiplexing, i.e. combining or separating wavelengths, e.g. 1xN, NxM
• CPC Class Codes: G02B 6/29395 configurable, e.g. tunable or reconfigurable switching G02B6/35
• CPC Class Codes: G02B 6/3516 the reflective optical element moving along the beam path, e.g. controllable diffractive effects using multiple micromirrors within the beam
• CPC Class Codes: G02B 6/356 in an optical cross-connect device, e.g. routing and switching aspects of interconnecting different paths propagating different wavelengths to (re)configure the various input and output links switching polarized beams G02B6/3594; power equalizers G02B6/356 and G02B6/3594; path selecting means H04Q11/0001
• CPC Class Codes: G02B 6/357 Electrostatic force electrostatic forces controlling reflecting elements in general G02B26/0841
• CPC Class Codes: H04J 14/0212 using optical switches or wavelength selective switches [WSS]

Abstract

The interferometer comprises a beam splitter, a mirror and a phase modulator. The beam splitter splits a signal into a first portion and a second portion. The mirror reflects the first portion. The first portion includes an optical path length, which is fixed. The phase modulator includes a selectively actuated reflective element to reflect the second portion. The second portion includes an optical path length, which is variable. The reflective element is selectively actuated between a first position and a second position to vary the optical path length of the second portion. When the reflective element is in the first position, the first portion and the second portion constructively interfere thereby directing the component signal along a first output path. When the reflective element is in the second position, the first portion and the second portion destructively interfere thereby directing the component signal along a second optical path. An array of interferometers combined with polarization diversity micro-optics module, static diffraction grating, and simple free-space optics is used for selectively passing and dropping first component signals of a first wavelength division multiplexed (WDM) signal and for selectively adding second component signals of a second WDM signal to the first WDM signal.

Claims

1. An apparatus for selectively passing and dropping first component signals of a first wavelength division multiplexed (WDM) signal and for selectively adding second component signals of a second WDM signal to the first WDM signal, the apparatus comprising:

a. a first optical train to direct each component signal of the first WDM signal along a corresponding one of a plurality of first optical paths;

b. a second optical train to direct each component signal of the second WDM signal along a corresponding one of a plurality of second optical paths;

c. an array of interferometers configured to receive the first component signals along the plurality of first optical paths and the second component signals along the plurality of second optical paths, each interferometer including a beam splitter to receive a first signal along the first optical path and a second signal along the second optical path, and to split each signal into a first portion and a second portion, a first mirror to reflect the first portion of each signal wherein an optical path length of the first portion is fixed, a phase modulator including a selectively actuated reflective layer to reflect the second portion of each signal wherein an optical path length of the second portion is variable, the phase modulator including a support structure and a substrate, the reflective layer forming a single elongated element suspended above the substrate, the reflective layer being configured to deflect in a direction substantially normal to the substrate;

a first de-multiplexer configured to de-multiplex the first WDM signal into the first component signals, a second de-multiplexer configured to de-multiplex the second WDM signal into the second component signals;

a first multiplexer configured to multiplex all first and second component signals directed back along the first optical path and a second multiplexer configured to multiplex all first and second component signals directed back along the second optical path;

wherein the first de-multiplexer and the second de-multiplexer each comprise a diffraction grating configured to direct a component signal to a corresponding beam splitter by way of a transform lens and a second mirror;

whereby the reflective layer is selectively actuated between a first position and a second position to vary the optical path length of the second portion such that when the reflective layer is in the first position, the first portion and the second portion of the first signal constructively interfere and the first portion and the second portion of the second signal constructively interfere thereby directing the first signal back along the first optical path and the second signal back along the second optical path, and when the reflective layer is in the second position, the first portion and the second portion of the first signal destructively interfere and the first portion and the second portion of the second signal destructively interfere thereby directing the first signal along the second optical path and the second signal along the first optical path.

2. The apparatus according to claim 1, wherein the first multiplexer and the first de-multiplexer comprise a bi-directional multiplexer/de-multiplexer and the second multiplexer and the second de-multiplexer comprise a bi-directional multiplexer/de-multiplexer.

3. The apparatus according to claim 1 wherein the first optical train and the second optical train are comprised of free-space optics including a polarization diversity module on each input port of the apparatus.

4. The apparatus according to claim 1 wherein the first portion and the second portion are both reflected back to the beam splitter, and the first portion and the second portion are recombined at the beam splitter.

5. The apparatus according to claim 4 wherein the first portion and the second portion return to the beam splitter in-phase when the reflective element is in the first position.

6. The apparatus according to claim 4 wherein the first portion and the second portion return to the beam splitter 180 degrees out-of-phase when the Reflective layer is in the second position.

7. The apparatus according to claim 1 further comprising a controller electrically coupled to each phase modulator within the array of interferometers to provide control signals for selectively actuating the reflective layer within each phase modulator.

8. The apparatus according to claim 1 wherein the difference between the optical path length in the first position and the second position is one-quarter wavelength of the first signal.