WO2001007945A1 - Ameliorations apportees a un commutateur a fibres optiques, compact, modulaire et souple - Google Patents

Ameliorations apportees a un commutateur a fibres optiques, compact, modulaire et souple Download PDF

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Publication number
WO2001007945A1
WO2001007945A1 PCT/US2000/020028 US0020028W WO0107945A1 WO 2001007945 A1 WO2001007945 A1 WO 2001007945A1 US 0020028 W US0020028 W US 0020028W WO 0107945 A1 WO0107945 A1 WO 0107945A1
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WO
WIPO (PCT)
Prior art keywords
switching module
fiber optic
light beam
optic switching
light
Prior art date
Application number
PCT/US2000/020028
Other languages
English (en)
Inventor
Armand P. Neukermans
Steven M. Clark
Marc R. Schuman
Timothy G. Slater
Jack D. Foster
Sam Calmes
Original Assignee
Nortel Networks Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Nortel Networks Corporation filed Critical Nortel Networks Corporation
Priority to US10/031,159 priority Critical patent/US6694072B1/en
Priority to JP2001512980A priority patent/JP2003517631A/ja
Priority to EP00947597A priority patent/EP1210627A1/fr
Priority to CA002379822A priority patent/CA2379822A1/fr
Publication of WO2001007945A1 publication Critical patent/WO2001007945A1/fr

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Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/35—Optical coupling means having switching means
    • G02B6/3586—Control or adjustment details, e.g. calibrating
    • G02B6/3588—Control or adjustment details, e.g. calibrating of the processed beams, i.e. controlling during switching of orientation, alignment, or beam propagation properties such as intensity, size or shape
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
    • G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
    • G02B26/0816—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light by means of one or more reflecting elements
    • G02B26/0833—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light by means of one or more reflecting elements the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
    • G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
    • G02B26/0816—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light by means of one or more reflecting elements
    • G02B26/0833—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light by means of one or more reflecting elements the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD
    • G02B26/0841—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light by means of one or more reflecting elements the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD the reflecting element being moved or deformed by electrostatic means
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
    • G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
    • G02B26/0816—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light by means of one or more reflecting elements
    • G02B26/0833—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light by means of one or more reflecting elements the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD
    • G02B26/085—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light by means of one or more reflecting elements the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD the reflecting means being moved or deformed by electromagnetic means
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/32—Optical coupling means having lens focusing means positioned between opposed fibre ends
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/32—Optical coupling means having lens focusing means positioned between opposed fibre ends
    • G02B6/327—Optical coupling means having lens focusing means positioned between opposed fibre ends with angled interfaces to reduce reflections
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q11/00—Selecting arrangements for multiplex systems
    • H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
    • H04Q11/0005—Switch and router aspects
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/35—Optical coupling means having switching means
    • G02B6/351—Optical coupling means having switching means involving stationary waveguides with moving interposed optical elements
    • G02B6/3512—Optical coupling means having switching means involving stationary waveguides with moving interposed optical elements the optical element being reflective, e.g. mirror
    • G02B6/3518—Optical coupling means having switching means involving stationary waveguides with moving interposed optical elements the optical element being reflective, e.g. mirror the reflective optical element being an intrinsic part of a MEMS device, i.e. fabricated together with the MEMS device
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/35—Optical coupling means having switching means
    • G02B6/354—Switching arrangements, i.e. number of input/output ports and interconnection types
    • G02B6/3554—3D constellations, i.e. with switching elements and switched beams located in a volume
    • G02B6/3556—NxM switch, i.e. regular arrays of switches elements of matrix type constellation
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/35—Optical coupling means having switching means
    • G02B6/3564—Mechanical details of the actuation mechanism associated with the moving element or mounting mechanism details
    • G02B6/3584—Mechanical details of the actuation mechanism associated with the moving element or mounting mechanism details constructional details of an associated actuator having a MEMS construction, i.e. constructed using semiconductor technology such as etching
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/36—Mechanical coupling means
    • G02B6/3628—Mechanical coupling means for mounting fibres to supporting carriers
    • G02B6/3648—Supporting carriers of a microbench type, i.e. with micromachined additional mechanical structures
    • G02B6/3652—Supporting carriers of a microbench type, i.e. with micromachined additional mechanical structures the additional structures being prepositioning mounting areas, allowing only movement in one dimension, e.g. grooves, trenches or vias in the microbench surface, i.e. self aligning supporting carriers
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/36—Mechanical coupling means
    • G02B6/3628—Mechanical coupling means for mounting fibres to supporting carriers
    • G02B6/3648—Supporting carriers of a microbench type, i.e. with micromachined additional mechanical structures
    • G02B6/3656—Supporting carriers of a microbench type, i.e. with micromachined additional mechanical structures the additional structures being micropositioning, with microactuating elements for fine adjustment, or restricting movement, into two dimensions, e.g. cantilevers, beams, tongues or bridges with associated MEMs
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/36—Mechanical coupling means
    • G02B6/3628—Mechanical coupling means for mounting fibres to supporting carriers
    • G02B6/3664—2D cross sectional arrangements of the fibres
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q11/00—Selecting arrangements for multiplex systems
    • H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
    • H04Q11/0005—Switch and router aspects
    • H04Q2011/0007—Construction
    • H04Q2011/0026—Construction using free space propagation (e.g. lenses, mirrors)
    • H04Q2011/003—Construction using free space propagation (e.g. lenses, mirrors) using switches based on microelectro-mechanical systems [MEMS]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q11/00—Selecting arrangements for multiplex systems
    • H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
    • H04Q11/0005—Switch and router aspects
    • H04Q2011/0037—Operation
    • H04Q2011/0039—Electrical control
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q11/00—Selecting arrangements for multiplex systems
    • H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
    • H04Q11/0005—Switch and router aspects
    • H04Q2011/0037—Operation
    • H04Q2011/0043—Fault tolerance

Definitions

  • the present invention relates generally to the technical field of fiber optics, and, more particularly, to free-space, reflective NxN fiber optic switches.
  • switches for fiber optic telephonic communica- tions exist which perform functions for fiber optic telephonic communications analogous to or the same as the crossbar switch and electronic switching systems perform for electrical telephonic communications.
  • the presently available fiber optic switches are far from ideal. That is, existing fiber optic telecommunications technology lacks a switch that performs the same function for optical telecommunications as that performed by electronic switching systems for large numbers of optical fibers.
  • One approach used in providing a 256x256 switch for fiber optic telecommunications first converts light received from a incoming optical fiber into an electrical signal, then transmits the electrical signal through an electronic switching network. The output signal from that electronic switching network is then used to generate a second beam of light that then passes into an output optical fiber.
  • the preceding approach for providing a 256x256 fiber optic switch is physically very large, requires electrical circuits which process extremely high-speed electronic signals, and is very expensive. Attempting to avoid complex electronic circuits and conversions between light and electronic signals, various proposals exist for assembling a fiber optic switch that directly couples a beam of light from one optical fiber into another optical fiber.
  • United States Patent No. 4,886,335 entitled "Optical Fiber Switch System” that issued December 12, 1989, includes a conveyor that moves ferrules attached to ends of optical fibers. The conveyer moves the ferrule to a selected adapter and plugs the ferrule into a coupler/decoupler included in the adapter. After the ferrule is plugged into the coupler/decoupler, light passes between the optical fiber carried in the ferrule and an optical fiber secured in the adapter.
  • the lxN switch using light reflected back into the moving optical fiber from the immediately adjacent end of the selected optical fiber, then more precisely aligns the end of the input optical fiber to the output optical fiber.
  • Pulsed light generated by radiation emitting devices ("REDs") associated with each optical fiber pass from the fiber to the selected optical fiber in the opposing group.
  • the pulsed light from the RED received by the selected optical fiber in the opposing group is processed to provide a signal that is fed back to the piezoelec- trie bender for pointing light from the optical fiber directly at the selected optical fiber.
  • optical switches Rather than mechanically effecting alignment of a beam of light from one optical fiber to another optical fiber either by translating or by bending one or both optical fibers, optical switches have been proposed that employ micromachined moving mirror arrays to selectively couple light emitted from an input optical fiber to an output optical fiber. Papers presented at OFC/IOOC '99, February 21-26, 1999, describe elements that could be used to fabricate s a three (3) stage fully non-blocking fiber optic switch, depicted graphically in FIG. 1. This fiber optic switch employs moving mirror arrays in which each polysilicon mirror can selectively reflect light at a 90° angle.
  • the complexity of the fiber optic switch illustrated in FIG. 1 is readily apparent.
  • a 1024x1024 fiber optic switch assembled in accordance with that proposal requires 4096 individual optical fibers for interconnecting between the 32x64 optical switching arrays 52a x and 52b k and the 32x32 optical switching arrays 58_.
  • the 32x64 optical switching arrays 52a x and 52b k and 32x32 optical switching arrays 58 require a total of 196,608 micromachined mirrors.
  • the polysilicon mirrors proposed for the fiber optic switch illustrated in FIG. 1 are curved rather than optically flat.
  • United States Patent No. 4,365,863 entitled “Optical Switch For a Very Large Number of Channels” that issued December 28, 1982, (“the '863 patent”) discloses disposing two (2) parallel arrays of optically opposed, regularly placed ends of optical fibers.
  • the space between the two (2) arrays contains an optical switching system that includes propagation mode converters that are associated respectively with each fiber of each array.
  • the mode converters convert light from the guided mode of propagation in glass filaments to a directive mode of propagation in free space, and vice-versa.
  • such a converter comprises essentially an optical lens whose focal point is positioned approximately at the end of the corresponding fiber.
  • the optical switching system of the '863 patent also includes a light beam deflector associated with each fiber of its two arrays. Any mode converter of one array sends a beam of light to a deflector with which it is associated. The deflector receiving the light beam from the mode converter redirects the light to any one of the deflectors associated with the other array of optical fibers. The deflector receiving the beam from a deflector redirects the light to the mode converter associated with the receiving light deflector.
  • the light beam deflectors may be of any known type.
  • the '863 patent specifically discloses using for light beam deflectors either a mechanical-optical device that operates on the principle of the diasporameter, or an acousto-optical deflectors based on photon-phonon interaction within a crystal medium.
  • Each light beam deflector in the '863 patent is controlled by an interface control that is driven by a logic circuit.
  • a detector is associated with each beam of light to extract from the signal carried by the beam the data corresponding to the address of the optical fiber in the respective arrays.
  • the logic circuits are connected to a central processor which, together with these logic circuits, controls all the functions of the switching system.
  • Each detector in the '863 patent may, for example, include a semi-transparent mirror sampling the corresponding beam of light, an optoelectronic device for converting the sample of the beam of light into an electrical signal, and a device for decoding this electrical signal in order to extract the optical fiber address data.
  • the present invention provides a fiber optic switch capable of concurrently coupling incoming beams of light carried on more than 1,000 individual optical fibers to more than 1,000 outgoing optical fibers.
  • An object of the present invention is to provide a simpler fiber optic switch that is capable of switching among a large number of incoming and outgoing beams of light carried on optical fibers.
  • Another object of the present invention is to provide a fiber optic switch which has low cross-talk between communication channels during switching thereof.
  • Another object of the present invention is to provide an highly reliable fiber optic switch.
  • Another object of the present invention is to provide a fiber optic switch that does not exhibit dispersion.
  • Another object of the present invention is to provide a fiber optic switch that is not polarization dependent.
  • the present invention is a fiber optic switching module adapted for use in a fiber optic switch that includes a first and a second group of optical fiber receptacles.
  • the two groups of optical fiber receptacles are separated from each other at opposite ends of a free space optical path.
  • Each optical fiber receptacle is adapted for receiving and fixing an end of an optical fiber.
  • the fiber optic switching module also includes lenses one of which is fixed respectively at each of the optical fiber receptacles of the first and second groups so the end of the optical fiber fixable in that optical fiber receptacle is juxtaposed with the lens fixed thereat.
  • Each lens is adapted for receiving a beam of light emittable from the juxtaposed end of the optical fiber and for emitting a quasi-collimated beam of light into the optical path of the fiber optic switching module.
  • the fiber optic switching module also includes a first and a second set of reflective light beam deflectors that are disposed in a V-shaped arrangement within the optical path between the groups of optical fiber receptacles.
  • Each of the light beam deflectors respectively is:
  • Also included in the fiber optic switching module is a mirror disposed along the optical path between the sets of light beam deflectors upon which quasi-collimated beams of light impinge.
  • a pair of light beam deflectors may be selected and oriented by the drive signals supplied thereto to establish an optical coupling for at least one quasi-collimated beam of light between a pair of lenses respectively fixable at any one of the optical fiber receptacles and another lens fixable at any other of the optical fiber receptacles.
  • FIG. 1 is a block diagram illustrating a proposed, prior art three (3) stage fully non-blocking fiber optic switch
  • FIG. 2 is a plan view ray tracing diagram illustrating propagation of light beams through a trapezoidally-shaped free space, convergent beam NxN reflective switching module in accordance with the present invention
  • FIG. 3 is a plan or elevational schematic diagram illustrating a single beam of light as may propagate between sides A and B of the trapezoidally-shaped free space, convergent beam NxN reflective switching module depicted in FIG. 2 in accordance with the present invention
  • FIG. 4a is a perspective view ray tracing diagram illustrating propagation of light beams through an alternative embodiment, rectangularly-shaped free space, convergent beam NxN reflective switching module in accordance with the present invention
  • FIG. 4b is plan view ray tracing diagram illustrating propagation of convergent light beams through the rectangularly- shaped reflective switching module illustrated in FIG. 4a in accordance with the present invention
  • FIG. 5 is a plan view ray tracing diagram illustrating propagation of light beams through an alternative embodiment, polygonally-shaped free space, convergent beam NxN reflective switching module in accordance with the present invention
  • FIG. 6 is a plan view ray tracing diagram illustrating propagation of light beams through a trapezoidally-shaped free space, convergent beam reflective switching module in accordance with the present invention that permits coupling a beam of light between any arbitrarily chosen pair of optical fibers;
  • FIG. 6a is a plan view ray tracing diagram illustrating free space propagation of light beams through a convergent beam reflective switching module in accordance with the present invention that has a V-shaped array of light beam deflectors, and that, similar to the switching module of FIG. 6, permits coupling a beam of light between any arbitrarily chosen pair of optical fibers;
  • FIG. 7 is a plan view ray tracing diagram illustrating propagation of light beams through an alternative trapezoidally- shaped free space, convergent beam NxN reflective switching module in accordance with the present invention which is more compact than the NxN reflective switching module depicted in FIG.
  • FIG. 8a is an elevational view illustrating a preferred, cylindrically shaped micro-lens adapted for use in the NxN reflective switching module
  • FIG. 8b is an elevational view illustrating a micro-lens adapted for use in the NxN reflective switching module that permits closer spacing between lenses and fibers;
  • FIG. 9 is a partially cross-sectioned elevational view illustrating a convergence block included both in the side A and in side B of the NxN reflective switching module depicted in FIG.
  • FIG. 10 is a partially cross-sectioned plan view illustrating the convergence block depicted in FIG. 9 that receives tapered optical fiber collimator assemblies;
  • FIG. 10a is a partially cross-sectioned plan view illustrat- ing an alternative convergence block that permits adjusting the position and orientation of the lenses;
  • FIG. 10b is a cross-sectioned elevational view illustrating of the alternative convergence block taken along the line lOa-lOa of FIG. 10a;
  • FIG. 11 is a partially cross-sectioned elevational view illustrating a micro-lens adapted for use in the NxN reflective switching module for concurrently switching light carried by a duplex pair of optical fibers;
  • FIG. 12 is an elevational view illustrating a preferred type of silicon wafer substrate used in fabricating torsional scanners
  • FIG. 13 is a plan view illustrating a 2D electrostatically energized torsional scanner particularly adapted for use in reflective switching modules such as those illustrated in FIGs. 2, 4a-4b, 5, 6, 6a and 7;
  • FIG. 14a is an enlarged plan view illustrating a torsional flexure hinge used in the torsional scanner taken along the line 14a-14a in FIG. 13;
  • FIG. 14b is an enlarged plan view illustrating a slotted torsion-bar hinge used in the torsional scanner taken along the line 14b-14b in FIG. 13;
  • FIG. 15 is a schematic cross-sectional elevational view illustrating a torsional scanner disposed above an insulating substrate having electrodes deposited thereon with a beam of light reflecting off a mirror surface located on the backside of a device layer;
  • FIGs. 15a and 15b are alternative plan views of the electrodes and a portion of the insulating substrate taken along the line 15a/15b-15a/15b in FIG. 15.
  • FIG. 16a is an elevational view illustrating a strip of torsional scanners adapted for use in reflective switching modules such as those illustrated in FIGs. 2, 4a-4b, 5, 6, 6a and V;
  • FIG. 16b is a cross-sectional plan view taken along the line 16b-16b in FIG. 16a illustrating overlapping immediately adjacent strips of torsional scanners to reduce the horizontal distance between immediately adjacent strips;
  • FIG. 16c is an elevational view illustrating a preferred strip of torsional scanners adapted for use in reflective switching modules such as those illustrated in FIGs. 2, 4a-4b, 5, 6, 6a and 7;
  • FIG. 16d is a cross-sectional plan view illustrating the preferred strip of torsional scanners taken along the line 16d-16d in FIG. 16c;
  • FIG. 16e is across-sectional plan view taken along the line 16d-16d in FIG. 16a illustrating juxtaposition of the strips of torsional scanners depicted in FIG. 16c;
  • FIG. 17a is a plan view illustrating vertically offset strips of torsional scanners which permits a denser arrangement of optical fibers in reflective switching modules such as those illustrated in FIGs. 2, 4a-4b, 5, 6, 6a and 7;
  • FIG. 17b is a plan view illustrating an even denser packing of offset rows or columns of torsional scanners that may be employed if all the torsional scanners are fabricated as a single monolithic array rather than in strips;
  • FIG. 18a is a plan view illustrating an alternative embodiment of the torsional scanner in which the outer torsional flexure hinges are oriented diagonally with respect to the scanner's outer frame;
  • FIG. 18b is a plan view illustrating an array of torsional scanner of the type illustrated in FIG. 18a;
  • FIG. 19a is a plan view illustrating an alternative embodiment of the torsional scanner in which the inner torsional flexure hinges are oriented along a diagonal of the scanner's non-square mirror plate;
  • FIG. 19b is a plan view illustrating an alternative embodiment of the torsional scanner depicted in FIG. 19a in which both pairs of torsional flexure hinges are suitably oriented with respect to crystallographic directions of silicon to permit fabrication of torsion sensors therein that have optimum characteristics;
  • FIG. 20a is an elevational view illustrating a dense arrangement of the torsional scanner illustrated in FIG. 18a adapted for inclusion in reflective switching modules such as those illustrated in FIGs. 2, 4a-4b, 5, 6, 6a and 7;
  • FIG. 20b is an elevational view illustrating a dense arrangement of the torsional scanner illustrated in FIG. 19a adapted for inclusion in reflective switching modules such as those illustrated in FIGs. 2, 4a-4b, 5, 6, 6a and 7;
  • FIG. 21 is a schematic cross-sectional elevational view illustrating an alternative embodiment strip of torsional scanners fastened to a substrate which also carries a mirror strip thereby permitting an arrangement in which collimator lenses and ends of optical fibers are positioned close to mirror surfaces on the torsional scanners;
  • FIG. 21a is a schematic elevational view illustrating arranging strips of torsional scanners illustrated in FIG. 21 to provide one dimensional convergence;
  • FIG. 21b is a schematic elevational view illustrating arranging optical fiber collimator assemblies to provide one dimensional convergence for combination with the one dimensional convergence of torsional scanners illustrated in FIG. 21a;
  • FIGs. 22a is a front elevational view of a strip of torsional scanners flip-chip bonded to a substrate
  • FIGs. 22b is a cross-sectioned, side elevational view of the strip of torsional scanners flip-chip bonded to the substrate taken along the line 22b-22b in FIG. 22a;
  • FIGs. 22c is a top view of the strip of torsional scanners that is flip-chip bonded to the substrate taken along the line 22c-22c in FIG. 22a;
  • FIGs. 22d is a cross-sectioned, side elevational view of the strip of torsional scanners flip-chip bonded to a silicon substrate having vias formed therethrough;
  • FIGs. 22e is a cross-sectioned, side elevational view of a portion of a surface of the torsional scanner having troughs formed therein to strengthen the bond to the substrate;
  • FIGs. 22f is a cross-sectioned, side elevational view similar to that of FIG. 22b showing a spacer interposed between the strip of torsional scanners and the substrate;
  • FIG. 23 is a ray tracing diagram illustrating scattering of light from portions of a torsional scanner that surrounds the mirror surface thereof;
  • FIG. 24 is a system level block diagram illustrating reflective switching modules such as those illustrated in FIGs. 2, 4a-4b, 5, 6, 6a and 7;
  • FIG. 25 is a perspective drawing illustrating a modular fiber optic switch in accordance with the present invention.
  • FIG. 26 is a overall block diagram for modular fiber optic switch depicted in FIG. 25 including a portcard and the reflective switching module;
  • FIG. 26a is a diagram illustrating one embodiment of photo- detectors that may be used in an optical alignment servo for precisely orienting a pair of mirrors included in the reflective switching module;
  • FIG. 26b is a diagram illustrating a compound photo-detector that may be used in an optical alignment servo for precisely orienting a pair of mirrors included in the reflective switching module;
  • FIG. 26c is a diagram schematically illustrating how bent- fiber taps may be used on portcards to extract light from an optical fiber for alignment and other diagnostic purposes;
  • FIG. 26d is an elevational view of a bent-fiber tap taken along the line 26d-26d in FIG. 26c;
  • FIG. 27a is a block diagram illustrating a servo system which ensures precise alignment of mirrors included in a reflective switching module included in the modular fiber optic switch depicted in FIG. 25, such as one of the reflective switching modules illustrated in FIGs. 2, 4a-4b, 5, 6, 6a and 7;
  • FIG. 27b is a block diagram illustrating one channel, either x-axis or y-axis, of a dual axis servo included in the servo system depicted in FIG. 27a;
  • FIG. 27c is a block diagram illustrating sharing a single channel of one dual axis servo among several different pairs of torsional scanner electrodes 214;
  • FIG. 27d is a block diagram illustrating a circuit for inducing controlled rotation of a torsional scanner using alternating current ("AC") driving voltages;
  • AC alternating current
  • FIGs. 27e and 27f are waveform diagrams illustrating voltages applied between electrodes and the mirror plate of the torsional scanner
  • FIG. 28a is a partially cross-sectioned elevational view illustrating an alternative embodiment double plate structure for receiving and fixing an array of optical fibers
  • FIG. 28b is an elevational view illustrating a profile for one type of hole that may be formed through one of the plates taken along the line 28b-28b in FIG. 28a;
  • FIG. 28c is an elevational view illustrating an array of XY micro-stages formed in one of the plates taken along the line 28c-28c in FIG. 28a;
  • FIG. 29a is an elevational view illustrating an XY micro- stage of a type included array taken along the line 29a-298 in FIG. 28c;
  • FIGs. 29b and 29c are elevational views illustrating a portion of alternative embodiment XY micro-stages taken along the line 29b/29c-29b/29c in FIG. 29a;
  • FIG. 30a is a partially cross-sectioned view illustrating a lens micromachined from a silicon substrate that can be electrostatically activated to move along the lens' longitudinal axis;
  • FIG. 30b is an elevational view illustrating the silicon micromachined lens taken along the line 30b-30b in FIG. 30a;
  • FIG. 30c is a partially cross-sectioned view illustrating a lens micromachined from a silicon substrate, similar to the lens illustrated in FIG. 30a, that can be electro-magnetically activated to move along the lens' longitudinal axis;
  • FIG. 31a is a plan view illustrating one configuration for using magnetic force in effecting rotation of torsional scanners
  • FIG. 31b is an elevational view of a magnet used therein taken along the line 31b-31b in FIG. 3la;
  • FIG. 31c is a plan view illustrating another configuration for using magnetic force in effecting rotation of torsional scanners
  • FIG. 3Id is an elevational view of a magnet used therein taken along the line 31d-31d in FIG. 31c;
  • FIG. 32 is an elevational view that illustrates coupling beams of light from a routing wavelength demultiplexer directly into one of the reflective switching modules illustrated in FIGs. 2, 4a-4b, 5, 6, 6a and 7;
  • FIG. 33a and 33b are respectively schematic diagrams illustrating a Littrow cavity formed by a grating formed on a 2D torsional scanner together with a laser-diode, and as applied for wavelength conversion that can be advantageously applied in telecommunication;
  • FIG. 34 is a schematic diagram illustrating using a torsional scanner carrying a grating for monitoring wavelengths of light that propagate along an optical fiber.
  • FIG. 2 depicts ray tracings for light beams propagating through a trapezoidally-shaped, convergent beam, double bounce
  • the NxN reflective switching module 100 includes sides 102a and 102b which are spaced apart from each other at opposite ends of a C-shaped free space optical path. Although as described below other geometrical relationships for the sides 102a and 102b may occur for other configurations of the NxN reflective switching module 100, for the embodiment of the NxN reflective switching module 100 illustrated in FIG. 2 having the C-shaped free space optical path the sides 102a and 102b are preferably coplanar. Both side 102a and side 102b are adapted to receive and fix ends 104 of N optical fibers 106, for example one- thousand one-hundred fifty-two (1152) optical fibers 106.
  • N optical fibers 106 for example one- thousand one-hundred fifty-two (1152) optical fibers 106.
  • the N optical fibers 106 are arranged in a rectangular array with thirty-six (36) columns, each of which contains thirty-two (32) optical fibers 106.
  • a lens 112 is disposed immediately adjacent to the ends 104 of each of the optical fibers 106 along the optical path between sides 102a and 102b.
  • Each of the lenses 112 are disposed with respect to the end 104 of the optical fiber 106 with which it is associated to produce from light, which may be emitted from the end 104 of the associated optical fiber 106, a quasi-collimated beam that propagates along the optical path between sides 102a and 102b.
  • FIG. 3 graphically illustrates a single beam of light 108 from a single optical fiber 106 as may propagate between sides 102a and 102b, or conversely.
  • the lens 112 is a micro-lens which typically has a focal length of 2.0 to 12.0 mm.
  • Such a lens 112 produces a quasi-collimated beam preferably having a diameter of approximately 1.5 mm which propagates along a five-hundred (500) to nine-hundred (900) mm long path between the sides 102a and 102b.
  • the NxN reflective switching module 100 preferably uses the maximum relay length of the lens 112, the end 104 of each optical fiber 106 is positioned at the focal length of the lens 112 plus the Raleigh range of the beam of light 108 emitted from the optical fiber 106. Consequently, if the end 104 of the optical fiber 106 is displaced a few microns along the axis of the lens 112, that produces a negligible effect on the direction along which the maximum relay length quasi-collimated beam propagates between the sides 102a and 102b. Typically the exit angle of the maximum relay length quasi-collimated beam from the lens 112 will be a fraction of one milliradian, i.e. 0.001 radian.
  • any possible misalignment of the maximum relay length quasi-collimated beam due to misalign- ment between the end 104 of the optical fiber 106 and the lens 112 can be easily accommodated by providing sufficiently large surfaces from which the beam reflects.
  • a beam of light 108 emitted from the end 104 of each optical fiber 106 reflects first off a mirror surface 116a or 116b, indicated by dashed lines in FIG. 3, that is associated with a particular lens 112 and optical fiber 106 pair.
  • the mirror surfaces 116 are preferably provided by two-dimensional ("2D") torsional scanners of a type similar to those described in United States Patent No. 5,629,790 (“the '790 patent”) , that is incorporated herein by reference.
  • the NxN reflective switching module 100 includes two sets 118a and 118b of mirror surfaces 116 respectively disposed between the lenses 112 along the optical path between the sides 102a and 102b.
  • Each set 118a or 118b includes a number of individual, independent mirror surfaces 116, each of which is supported by a pair of gimbals that permits each mirror surface 116 to rotate about two non-parallel axes.
  • the number of mirror surfaces 116 equals the number, N, of optical fibers 106 and lenses 112 at the nearest side 102a or 102b. After reflecting off the mirror surface 116a or 116b, the beam of light 108, propagating between sets 118a and 118b in FIG.
  • FIGs. 4a-4b depict ray tracings for light beams propagating through an alternative embodiment, rectangularly-shaped, convergent NxN reflective switching module 100.
  • the rectangularly-shaped configuration of the NxN reflective switching module 100 illustrated in FIGs. 4a-4b employs a horizontally-elongated Z-shaped free space optical path. While in the illustration of this FIG. the distances between the side 102a and the curved set 118a, the curved set 118a and the curved set 118b, the curved set 118b and the side 102b are substantially equal, those skilled in the art will recognize that these distances need not be equal.
  • the sets 118a and 118b may be curved to provide either one dimensional ("ID") or 2D convergence.
  • ID one dimensional
  • the curved set 118a may be advantageously moved nearer to the side 102a and the curved set 118b moved nearer to the side 102b.
  • Such a shortening of the distances between the sides 102a and 102b and the curved sets 118a and 118b correspondingly lengthens the distance between the curved set 118a and curved set 118b which produces a parallelogram-shaped NxN reflective switching module 100.
  • FIG. 5 depicts ray tracings for light beams propagating through an alternative embodiment, polygonally-shaped NxN reflective switching module 100.
  • the polygonally-shaped configuration of the NxN reflective switching module 100 illustrated in FIG. 5 also produces a Z-shaped free space optical path.
  • FIG. 6 depicts a trapezoidally-shaped reflective switching module 100 that consist of only one half of the NxN reflective switching module 100 depicted in FIG. 1, i.e. either the left half thereof or the right half thereof.
  • the reflective switching module 100 depicted in FIG. 6 fundamentally differs from that depicted in FIG. 1 only by including a mirror 120 disposed at the middle of the optical path between sides 102a and 102b.
  • the mirror 120 should have as high a reflectivity as possible at the relevant wavelengths of light, with the s and p reflectivity balanced, as is well known in the art.
  • the reflective switching module 100 depicted in FIG. 6 can couple light selectively between only one-half as many optical fibers 106 as the NxN reflective switching module 100 illustrated in FIG. 1, the reflective switching module 100 depicted in FIG. 6 can couple light between any arbitrarily chosen pair of those optical fibers 106.
  • FIG. 6a depicts another type of NxN reflective switching module 100 assembled by abutting two, mirror-image reflective switching modules of the general type illustrated in FIG. 6.
  • the configuration for the reflective switching module 100 illustrated in FIG. 6 includes sides 102a and 102b with the sets 118a and 118b of mirror surfaces 116 arranged to form a V-shape.
  • the arrangement of mirror surfaces 116 and sides 102a and 102b illustrated in FIG. 6a has some advantages over the arrangement depicted in FIG. 6.
  • the set 118a and side 102a are divided into two parts, i.e. the sides 102a and 102b and the sets 118a and 118b.
  • Dividing the sides 102a and 102b and the sets 118a and 118b into two parts reduces the distance between the sides 102a and 102b and their corresponding sets 118a and 118b of mirror surfaces 116 without increasing the deflection angles needed to couple light between any two arbitrarily chosen optical fibers 106.
  • This arrangement allows building reflective switching modules 100 having a larger number of optical fibers 106 by easing the collimator pointing tolerance.
  • FIG. 7 depicts another trapezoidally shaped NxN reflective switching module 100 which also employs a mirror 120 for folding the optical path of the NxN reflective switching module 100 depicted in FIG. 5. Folding the optical path into a W-shape provides a more compact reflective switching module 100 than the NxN reflective switching module 100 depicted in FIG. 1.
  • the various different embodiments of the reflective switching module 100 described above and illustrated in FIGs. 2, 4a, 4b, 5, 6, 6a, and 7 differ principally in the location of the mirror surfaces 116a and 116b along the beam of light 108, and in the folding of the optical path.
  • the mirror surfaces 116a and 116b are located approximately one-third ( 3 ) of the path length between the sides 102a and 102b from the nearest lenses 112.
  • the mirror surfaces 116a and 116b are immediately adjacent to the respective sides 102a and 102b.
  • those skilled in the art of optical design will readily understand that differences among the various configurations, particularly locations for the mirror surfaces 116a and 116b with respect to the lenses 112 and the ends 104 of the optical fibers 106, influence or affect other more detailed aspects of the optical design.
  • the beam of light 108 produced by the lens 112 from light emitted from the end 104 of the associated optical fiber 106 first impinges upon the associated mirror surface 116 of one of the torsional scanners included in the sets 118a and 118b.
  • the mirror surfaces 116 are preferably provided by thirty-six (36) linear strips of thirty-two (32) torsional scanners.
  • all thirty-two (32) mirror surfaces 116 in each strip are substantially coplanar.
  • immediately adjacent mirror surfaces 116 may be spaced 3.2 mm apart, and the immediately adjacent columns of mirror surfaces 116 are preferably spaced 3.2 mm apart with respect to the beams of light 108 impinging thereon from the immediately adjacent sides 102a and 102b.
  • the ends 104 of the optical fibers 106, the lenses 112, and the mirror surfaces 116 of un-energized torsional scanners are preferably oriented so all of the beams of light 108 produced by light emitted from optical fibers 106 having their ends 104 at the side 102a preferably converge at a point 122b that is located behind the set 118b of mirror surfaces 116 in the illustrations of FIGs. 2 and 7.
  • the beams of light 108 emitted from optical fibers 106 having their ends 104 at the side 102b in those FIGs. preferably converge at a point 122a that is located behind the set 118a of mirror surfaces 116.
  • the location of the point at which the beams of light 108 converge depend upon specific details of the NxN reflective switching module 100.
  • the beams of light 108 preferably converge at a point 122 that is located approximately behind a juncture of the sets 118a and 118b.
  • the convergence point 122 is established by considering mirror surfaces 116 at opposite sides of the sets 118a and 118b.
  • the point 122 lies at the intersection of two lines that respectively bisect angles having their vertices at those two mirror surface 116 and sides which extend from the respective mirror surfaces 116 through mirror surfaces 116 at opposite ends of the other set 118b or 118a.
  • the point 122 is located vertically one-half the height of the sets 118a and 118b.
  • the geometrical arrangement of the ends 104 of the optical fibers 106, the lenses 112, and the mirror surfaces 116 which produces the preceding convergence provides equal clockwise and counterclockwise rotation angles and minimal rotation angles for mirror surfaces 116 for each of the sets 118a and 118b that exhibit the greatest movement in reflecting a beam of light 108 from one mirror surface 116 in the set 118a or 118b to any of the mirror surfaces 116 in the other set 118b or 118a. If in the configuration for the NxN reflective switching module 100 depicted in FIG. 7 a pair of mirror surfaces 116a and 116b are separated six- hundred and fifty (650) mm along the beam of light 108, then the maximum angular rotation of the mirror surfaces 116 is approximately 3.9° clockwise and counter-clockwise.
  • a monolithic block is preferably used that has holes appropriately pre-drilled therein. Each pre-drilled hole receives one of the lenses 112 and a conven- tional optical fiber ferrule secured about the end 104 of one optical fiber 106.
  • the compound angles required to align the optical fiber 106 and the lens 112 for 2D convergence of the beams of light 108 are provided by suitably orienting the holes drilled into the block.
  • FIG. 8a depicts a preferred, cylindrically shaped micro-lens 112 fabricated with its focal point at, or as close as possible to, a face 138 of the lens 112.
  • the optical fiber 106 emits the beam of light 108 at an angle with respect to a center line of the optical fiber 106 because the end 104 is polished at an angle to eliminate reflections back from the end 104. Because the end 104 is angled, the axis of the beam of light 108 emitted from the end 104 diverges from the longitudinal axis of the optical fiber 106.
  • the face 138 of the lens 112 is angled to center the beam of light 108 within the lens 112.
  • the end 104 of the optical fiber 106 is positioned one Raleigh range of the beam of light 108, e.g. 50-60 microns, from the face 138.
  • the diameter of a cylindrical surface 136 of the lens 112 is made sufficiently large to contain the diverging beam of light 108 before it exits the lens 112 through a convex surface 142 as the quasi-collimated beam of light 108.
  • This configuration for the lens 112 and the end 104 of the optical fiber 106 centers the beam of light 108 about the longitudinal axis 144 of the lens 112 at the convex surface 142 of the lens 112, with the quasi-collimated beam of light 108 oriented essentially parallel to the longitudinal axis 144.
  • Usual manufacturing tolerances for the lens 112 described above produce acceptable deviations in exit angle and offset of the beam of light 108 from the longitudinal axis 144 of the lens 112.
  • the lens 112 is fabricated from BK7 optical glass and the end 104 of the optical fiber 106 angles at 8°, then the angle of the beam of light 108 within the lens 112 is 6.78°, and the lateral offset from the longitudinal axis 144 is less than 50 microns both at the face 138 and also 140 mm from the face 138.
  • This lens 112 is preferably made from Gradium material marketed by LightPath Technologies, Inc. FIG.
  • the lens 112 includes a smaller diameter surface 132 which a conically-shaped optical fiber collimator assembly 134 illustrated in FIG. 9 receives.
  • the larger diameter surface 136 of the lens 112 protrudes out of the optical fiber collimator assembly 134.
  • the champagne cork shaped embodiment of the micro- lens 112 may be fabricated by grinding down a portion of the lens 112 illustrated in FIG. 8a.
  • each optical fiber collimator assembly 134 also provides a receptacle that receives a conventional fiber optic ferrule 146 secured about the end 104 of the optical fiber 106.
  • a convergence block 152 one of which is respectively disposed at both sides 102a and 102b of the reflective switching module 100, is pierced by a plurality of conically shaped holes 154 as illustrated in FIG. 10 that equal in number to the number N of optical fibers 106.
  • Convergence of the beams of light 108 as described above is effected by the alignment of the optical fiber collimator assemblies 134 upon insertion into the holes 154.
  • the optical fiber collimator assemblies 134 and holes 154 are preferably formed from the same material with identically shaped, mating, conical surfaces that taper at an angle of a few degrees. Configured in this way, when all optical fiber collimator assemblies 134 carrying the optical fibers 106 are fully seated into their mating holes 154, the optical fiber collimator assemblies 134 becomes fixed in the convergence block 152 and hermetically seal the interior of the reflective switching module 100 through which the quasi-collimated beams of light 108 propagate.
  • the convergence block 152 may be simply machined out a single piece of metal such as stainless steel, or from a ceramic material, etc.
  • the convergence block 152 may be made out of Kovar, 42 % nickel-iron alloys, titanium (Ti) , tungsten (W) or molybdenum (Mo) suitably plated for corrosion resistance. These materials all have coefficients of expansion which approximately match that of the lenses 112 and minimize birefringent effects that may take place as lenses 112 are heated or cooled in their operating environment.
  • either ID or 2D convergence may also be obtained in other ways.
  • the configuration of the optical fibers 106 and the lenses 112 could provide some of the convergence which the arrangement of the mirror surfaces 116 upon which the beams of light 108 first impinge could provide the remainder of the convergence.
  • the mirror surfaces 116 in each column could be arranged along a cylindrical surface.
  • the optical fibers 106 and the lenses 112 might be arranged to provide none of the convergence, i.e.
  • beams of light 108 propagate parallel from the sides 102a and 102b to the first mirror surfaces 116, with the mirror surfaces 116 being arranged to provide all of the convergence as illustrated in FIGs. 4a-4b.
  • the mirror surfaces 116 in each column could be arranged along a spherical surface.
  • the optical fibers 106, lenses 112, and sets 118a and 118b of mirror surfaces 116 may be arranged to provide either ID or 2D convergence either behind the sets 118a and 118b or at the sets 118a and 118b.
  • Machining the convergence block 152 out a single piece of metal as described previously to provide convergence for the beams of light 108 means that individual holes 154 are under compound complex angles with respect to each other.
  • the beam of light 108 emitted from each optical fiber collimator assembly 134 must be oriented to impinge directly on the mirror surface 116 immediately in front of the lens 112. If the beam of light 108 misses the mirror surface 116 slightly, the beam of light 108 will loose a substantial amount of power during during transmission through the reflective switching module 100. In fact, a substantial misalignment between the beam of light 108 emitted from a particular lens 112 and the corresponding mirror surface 116 might render the optical fiber 106 inoperable. Consequently, alignment of each beam of light 108 with its corresponding mirror surface 116 is essential for proper operation of the reflective switching module 100.
  • each optical fiber 106 is positioned at the focal length of the lens 112 plus the Raleigh range of the beam of light 108 emitted from the optical fiber 106.
  • the lens 112 typically exhibits more centration error.
  • the longitudinal axis 144 of the lens 112 tilts slightly with respect to the optical fiber 106 due to variations in the lens 112 and the optical fiber collimator assembly 134.
  • the ferrule 146 and the lens 112 may be misaligned. For all of these reasons, a structure that provides an alternative to the structure depicted in FIGs. 9 and 10, and which permits adjusting the position and orientation of the lens 112 is highly desirable.
  • the hole 154 that receives the lens 112 and the optical fiber 106 is drilled in solid material forming the convergence block 152 as illustrated in FIG. 10a.
  • a face 156 thereof is then slit in various directions through the holes 154 to a depth slightly greater than the length of the lenses 112.
  • more material may be removed from the face 156 around each hole 154 so each lens 112 may be held by three (3) arcuate, deforable posts, 157 as illustrated in FIG. 10b.
  • This provides a mounting for the lens 112 that is monolithically integrated into the convergence block 152, protrudes outward from it, and is plastically deformable.
  • the lenses 112 are initially secured in the convergence block 152 preferably by impact centration. During impact centration, the posts 157 flow around the lens 112, and hold the lens 112 in place. Then, ferrules 146, each respectively carrying the end 104 of one optical fiber 106, are inserted into individual holes 154 in the convergence block 152. The ferrules 146 are then adjusted length wise within the holes 154 so each beam of light 108 focuses at the proper place within the reflective switching module 100, which is typically halfway between the sets 118 of mirror surfaces 116. After focusing, each ferrule 146 is then preferably fixed to the convergence block 152 by impact.
  • This system for impact mounting of optical fibers 106 can produce an alignment with 2 microns of concentric- ity between the ferrule 146 and the optical fiber 106.
  • the concentricity between the ferrule 146 and the hole 154 may also be held to a few microns.
  • each lens 112 aligns exactly with the corresponding optical fiber 106.
  • the beam of light 108 emitted from the lens 112 is monitored using a camera or by some other means while orienting the beam of light 108 by plastically deforming the supporting posts 157.
  • each lens 112 may be tilted and displaced so the beam of light 108 emitted therefrom impinges directly on the mirror surface 116 immediately in front of the lens 112.
  • optical fibers are generally matched as a duplex pair in which one fiber carries communications in one direction while the other fiber of the pair carries communications in the opposite direction.
  • Connectors adapted for coupling light between two duplex pairs of optical fibers which secure the two optical fibers of a pair in a single ferrule are presently available.
  • FIG. 11 depicts a lens 112 adapted for use in the reflective switching module 100 for concurrently switching light carried by a duplex pair of optical fibers 106a and 106b. As illustrated in FIG.
  • the duplex optical fiber ferrule 146 carries the duplex pair of optical fibers 106a and 106b.
  • the ends 104a and 104b of the optical fibers 106a and 106b and the faces 138a and 138b of the lens 112 are all polished at an angle.
  • the angles of the faces 138a and 138b are formed to compensate for the off- axis position of the optical fibers 106a and 106b so beams of light 108a and 108b impinging upon faces 138a and 138b from the optical fibers 106a and 106b are formed into quasi-collimated beams which exit the convex surface 142 parallel to but slightly offset from the longitudinal axis 144, and propagate in that way through the reflective switching module 100.
  • Both of the beams of light 108a and 108b impinge upon the same pair of mirror surfaces 116a and 116b which are made large enough to simultaneously reflect both beams of light 108a and 108b.
  • the lens 112 located there couples the beams of light 108a and 108b into the respective optical fibers 106 of the duplex pair.
  • the mirror surfaces 116a and 116b of the sets 118a and 118b are preferably provided by electrostatically energized 2D torsional scanners of a type described in the '790 patent.
  • Hinges which permit the mirror surfaces 116 to rotate about two (2) non-parallel axes preferably include torsion sensors of a type disclosed in United States Patent No. 5,648,618 (“the '618 patent”) that is also incorporated herein by reference.
  • torsional scanners are preferably fabricated by micro-machining single crystal silicon using Simox, silicon- on-insulator or bonded silicon wafer substrates. Such wafer substrates are particularly preferred starting material for torsional scanner fabrication because they permit easily fabricating a very flat, stress-free membrane, possibly only a few microns thick, which supports the mirror surfaces 116. As illustrated in FIG.
  • a silicon-on-insulator (“SOI") wafer 162 includes an electrically insulating silicon dioxide layer 164 that separates single crystal silicon layers 166 and 168. Torsion bars and plates that carry the mirror surfaces 116 of torsional scanners are formed in the thinner device silicon layer 166 while other portions of torsional scanners are formed by backside etching in the thicker handle silicon layer 168. As is well known to those skilled in the art of micro-machining, the device silicon layer 166 has a frontside 169 furthest from the handle silicon layer 168 and a backside 170 at the silicon dioxide layer 164. The intermediate silicon dioxide layer 164 provides a perfect etch stop for etching the wafer 162 from its backside, and yields torsion bars and plates having uniform thickness.
  • FIG. 13 depicts a single electrostatically energized 2D torsional torsional scanner 172 adapted for providing the mirror surfaces 116 for the reflective switching module 100.
  • the torsional scanner 172 includes an outer reference frame 174 to which are coupled a diametrically opposed pair of outer torsional flexure hinges 176.
  • the torsional flexure hinges 176 support an inner moving frame 178 for rotation about an axis established by the torsional flexure hinges 176.
  • a diametrically opposed pair of inner slotted torsion-bar hinges 182 couple a central plate 184 to the inner moving frame 178 for rotation about an axis established by the torsion-bar hinges 182.
  • the axes of rotation established respectively by the torsional flexure hinges 176 and by the torsion-bar hinges 182 are non-parallel, preferably perpendicular.
  • the plate 184 of the torsional scanner 172 is rectangularly shaped with the longer side being approximately 1.4 times wider than the height of the plate 184.
  • the plate 184 included in the reflective switching module 100 has a rectangular shape because the beam of light 108 impinges obliquely at an angle of 45° on the mirror surface 116 carried by the plate 184. Consequently, for reflection of the beam of light 108 from the mirror surface 116 the rectangularly shaped plate 184 becomes effectively square.
  • the plate 184 is preferably 2.5 mm x 1.9 mm, and is typically between 5 and 15 microns thick as are the inner moving frame 178, the torsional flexure hinges 176 and torsion-bar hinge 182.
  • the torsional flexure hinges 176 and torsion-bar hinge 182 are between 200 and 400 microns long, and between 10 and 40 microns wide. The resonance frequencies on both axes are on the order of 400 to 800 Hz which permits switching a beam of light 108 between two optical fibers 106 in approximately 1 to 5 milliseconds.
  • Both the frontside 169 and the backside 170 of the plate 184 are coated in perfect stress balance with identical metallic adhesion layers, preferably 10.0 to 100.0 A 0 of titanium (Ti) or zirconium (Zr) which underlie a 500 to 800 A 0 thick metallic reflective layer of gold (Au).
  • the torsional flexure hinges 176 which are illustrated in greater detail in FIG.
  • the torsion-bar hinges 182 are pierced by several longitudinal slits 186, e.g. four (4) or five (5), that are oriented parallel to the length of the torsion-bar hinges 182.
  • the slits 186 subdivide a single torsion bar into a number of much thinner individual bars that are much thicker than their width.
  • the torsion-bar hinges 182 are more compact than a conventional one- piece torsion bar having an equivalent torsional spring constant.
  • the torsion-bar hinges 182 provide more mode separation between the principal torsional vibration mode and the higher order modes than the torsional flexure hinges 176. Moreover, the torsion-bar hinges 182 are much stiffer than the torsional flexure hinges 176 in a direction perpendicular to the plate 184. Consequently, use of the torsional flexure hinges 176 and torsion-bar hinges 182 instead of a conventional unfolded torsion bar permits making much smaller torsional scanners 172 that can be packed more closely together which correspondingly increases the number of optical fibers 106 that may be accommodated at the sides 102a and 102b of the reflective switching module 100.
  • Each torsional scanner 172 included in the reflective switching module 100 includes a pair of torsion sensors 192a and 192b, of a type disclosed in the '618 patent.
  • the torsion sensors 192a and 192b measure orientation of the supported member, i.e. the plate 184 or the inner moving frame 178, with respect to the supporting member, i.e. the inner moving frame 178 or the outer reference frame 174, at a theoretical resolution of approximately 1.0 micro-radians.
  • an electrical current flows in series through the two torsion sensors 192a and 192b between a pair of sensor-current pads 194a and 194b.
  • the torsional scanner 172 includes a meandering metal conductor 196 that is bonded to the frontside 169 of the device silicon layer 166.
  • the meandering metal conductor 196 crosses the immediately adjacent torsional flexure hinge 176 from the outer reference frame 174 onto the inner moving frame 178 to reach the X-axis torsion sensor 192b that is located in the lower torsion-bar hinge 182.
  • the meandering metal conductor 196 From the X-axis torsion sensor 192b the meandering metal conductor 196 continues onto a reflective, stress balanced metal coating, that is applied to both sides of the plate 184 to provide the mirror surface 116, and across the plate 184 and the upper torsion-bar hinge 182 back onto the inner moving frame 178. The meandering metal conductor 196 then leads to the Y-axis torsion sensor 192a that is located in the left hand torsional flexure hinge 176. From the Y-axis torsion sensor 192a, the meandering metal conductor 196 then curves around the outer reference frame 174 to the sensor-current pad 194b.
  • Metal conductors that are disposed on opposite sides of the meandering metal conductor 196 across the right hand torsional flexure hinge 176 and on the inner moving frame 178, connect a pair of inner-hinge sensor-pads 198a and 198b to the X-axis torsion sensor 192b.
  • metal conductors one of which is disposed along side the meandering metal conductor 196 on the outer reference frame 174 and the other with curves around the opposite side of the torsional scanner 172 on the outer reference frame 174, connect a pair of inner-hinge sensor-pads 202a and 202b to the Y-axis torsion sensor 192a.
  • a pair of grooves 204 cut only through the device silicon layer 166 on opposite sides of the inner-hinge sensor-pads 198a and 198b, increase electrical isolation between the sensor-current pad 194a and the inner-hinge sensor-pads 198a and 198b and the sensor-current pad 194b and the inner-hinge sensor-pads 202a and 202b.
  • the backside 170 of the plate 184 provides the mirror surface 116 because, as illustrated in FIG. 15, the frontside 169 faces an insulating substrate 212 which carries both electrodes 214 used in energizing rotation of the plate 184 and contacts for the sensor-current pads 194a and 194b, the inner-hinge sensor-pads 198a and 198b and the inner-hinge sensor-pads 202a and 202b not illustrated in FIG. 15.
  • the plates 184 of each torsional scanner 172 are separated a distance, e.g. from 40 to 150 microns, from the substrate 212 by spacers which are also not depicted in FIG 15.
  • the separation between the plate 184 and the substrate 212 depends upon how far edges of the plate 184 move during rotation. Note that for the reflective switching module 100 very thin plates 184, only a few microns thick, are desirable and can be fabricated using the device silicon layer 166 of the wafer 162. In many instances the plate 184 and the torsional flexure hinges 176 and torsion-bar hinge 182 can be made of the same thickness as the device silicon layer 166. Alternatively, as illustrated in FIG. 15 the torsional flexure hinges 176 may be thinned by etching. For example, the torsional flexure hinges 176 may be 6 microns thick while the plate 184 may be 10 microns thick. Analogously, the plate 184 may be thinned to reduce its moment of inertia by etching a cavity 216 into the plate 184 leaving reinforcing ribs 218 on the thinned plate 184.
  • a telecommunication system component such as the reflective switching module 100 must exhibit high reliability.
  • a plate 184 of the torsional scanner 172 that accidentally collides with the electrode 214 should not stick to it, and should immediately rotate to its specified orientation. Furthermore, such accidental collisions should not damage the torsional scanner 172, or any circuitry connected to the torsional scanner 172.
  • the periphery of the plate 184 and of the inner moving frame 178 have rounded corners that reduce the strength of the electrostatic field. Rounding the periphery of the plate 184 also reduces its effective turning radius which results from compound rotation of the plate 184 about the axes respectively established by both torsional flexure hinges 176 and torsion-bar hinge 182.
  • Electrodes 214 are overcoated with electrical insulating material 219 such as polyimide. Overcoating only those portions of the electrodes 214 which may contact the plate 184 with the electrical insulating material 219 avoids charge stored on most of the electrodes 214.
  • electrical insulating material 219 such as polyimide.
  • some of the silicon dioxide layer 164 may be left at the periphery of the plate 184 so the metallic reflective layer which provides the mirror surface 116 never contacts the electrode 214.
  • holes 220 are formed through the metal of the electrodes 214 in areas of possible contact.
  • the torsional scanner 172 is at a ground electrical potential while driving voltages are applied to the electrodes 214.
  • large resistors e.g. 1.0 MQ
  • these resistors should be located as close as practicable to the electrodes 214 otherwise the conductor connecting between the electrodes 214 and the resistors might pickup stray electric fields that rotate the plate 184. Therefore, one alternative is to overcoat the electrodes 214 with a very high resistivity but slightly conductive material in selected areas such as those illustrated in FIG. 16a to provide a bleed path from the electrodes 214 for DC charges.
  • inputs of all amplifiers connected to torsional scanners 172 should include diode protection to prevent damage from an over-voltage condition due to arcing or accidental contact between the plate 184 and the electrodes 214.
  • diode protection to prevent damage from an over-voltage condition due to arcing or accidental contact between the plate 184 and the electrodes 214.
  • the torsional scanners 172 are preferably arranged into strips 222 as illustrated in FIGs. 16a and 16b.
  • Each strip 222 includes a metal support frame 224 to which the substrate 212 is fastened.
  • the strip 222 is flip- chip bonded to the substrate 212 so all electrical connections to the strip 222 are made between the strip 222 and the substrate 212.
  • a flat polyimide backed multi-conductor ribbon cable 226 connects to the substrate 212 to exchange electrical signals between the pads 194, 198 and 202 and the electrodes 214. Since each support frame 224 may be an open frame possibly including reinforcing ribs, the ribbon cable 226 can be freely bent and guided away from the substrate 212.
  • FIG. 16b illustrates how, without obscuring the mirror surfaces 116, the substrates 212 and the strips 222 may be overlapped with the ribbon cable 226 serpentined along the staircased substrates 212. Arranging the strips 222 in this way reduces the horizontal distance between the mirror surfaces 116 of immediately adjacent strips 222 in relationship to the beams of light 108. Since the beams of light 108 impinge upon the mirror surfaces 116 at approximately 45°, the apparent distance between immediately adjacent strips 222 is further foreshortened by a factor of approximately 1.4 which, as described above, is why the plate 184 is preferably rectangularly shaped.
  • FIGs. 16c and 16d illustrate a preferred embodiment for the strips 222 and the support frames 224 in which electrical leads 228 that connect to the torsional scanners 172 are preferably provided by electrically conductive vias formed through the substrate 212.
  • the leads 228 can be plated or screened onto one face, around one edge, and onto the other face of the substrate 212. With this configuration for the leads 228, attachment of the ribbon cable 226 to the substrate 212 is unhindered. Plating or screening the leads 228 onto the substrate 212 and including some via holes through the substrate 212 permits the substrate 212 to be as narrow as the strip 222. Narrowed to this extent, the combined strips 222, substrates 212 and support frames 224 may now be arranged as illustrated in FIG.
  • the ribbon cables 226 can be attached to the substrates 212 as illustrated in FIGs. 16d and 16e by hot bar bonding. Electrical connections between the leads 228 on the substrate 212 and the multi-conductor ribbon cables 226 can be provided by solder, or, preferably, by anisotropically electrically conductive film. The mechanical attachment of the ribbon cable 226 to the substrate 212 can be reinforced by a strain-relief bead 229 of epoxy.
  • the density of the optical fibers 106 at the sides 102a and 102b may be increased by offsetting the torsional scanners 172 of immediately adjacent strips 222 vertically by one-half the vertical distance between torsional scanners 172 within the strip 222. Due to the convergence criteria set forth above for arranging the beams of light 108 within the reflective switching module 100, offsetting the torsional scanners 172 in immediately adjacent strips 222 effects a reorganization of the holes 154 which receive the optical fiber collimator assemblies 134 from a quasi rectangular array into a quasi hexagonally close packed array.
  • While offsetting the torsional scanners 172 in immediately adjacent strips 222 does not increase the density of the torsional scanners 172, such an arrangement of the torsional scanners 172 does increase the density of the optical fibers 106 at the sides 102a and 102b to the extent that the diameter, either of lenses 112 or of optical fiber collimator assemblies 134, limits the spacing between immediately adjacent optical fibers 106.
  • the density of torsional scanners 172 may be even further increased by fabricating the torsional scanners 172 as completely monolithic two dimensional arrays rather than as strips 222. As illustrated in FIG.
  • FIGs. 18a and 18b illustrate a diagonal configuration for the torsional flexure hinges 176 and torsion-bar hinge 182 which more efficiently uses area on the strips 222 than a configuration in which the torsional flexure hinges 176 and torsion-bar hinge 182 are oriented parallel and perpendicular to strips 222.
  • the plate 184 is elongated in one direction to accommodate the 45° impingement angle of the beam of light 108. Due to the elliptical shape of the beam of light 108 as it impinges upon the plate 184, corners of the beam of light 108 may be eliminated resulting in an octagonally shaped plate 184, which conveniently provides room for the outer reference frame 174. Sides of the outer reference frame 174 are oriented in the ⁇ 110> crystallo- graphic direction of silicon for ease of fabrication.
  • This configuration for the torsional scanner 172 orients the torsion sensors 192a and 192b along the ⁇ 100> crystallographic direction of silicon.
  • a wafer 162 having a p-type device silicon layer 166 or p-type implantation must be used in fabricating the torsion sensors 192a and 192b.
  • the ⁇ 110> and ⁇ 100> crystallographic directions of silicon may be interchanged with suitable process changes.
  • 1.5 x 2 mm plates 184 may be spaced only 2.5 mm apart effectively increasing the density of mirror surfaces 116 by a factor of 1.4.
  • the strips 222 slope at 54°.
  • the strips 222 are oriented at 45° to the support frames 224. This orientation of the strips 222 is necessary if the mirror surfaces 116 are to fully intercept the beams of light 108.
  • the support frames 224 could be oriented at 45° which permits all the strips 222 to be the same length, thereby using area on wafers 162 more efficiently.
  • FIG. 19a illustrates yet another alternative embodiment of the torsional scanner 172 which further reduces its size thereby further shortening distances between immediately adjacent mirror surfaces 116 in the reflective switching module 100. From the preceding description it is apparent that positioning the torsional flexure hinges 176 and torsion-bar hinge 182 at corners rather than sides of the plate 184 advantageously reduces the size of the torsional scanner 172.
  • an elliptically- shaped curve 232 represents an outline of the beam of light 108 impinging on the mirror surface 116 of the plate 184.
  • the inner torsion-bar hinges 182 may be rotated with respect to the plate 184 to occupy unused corner space.
  • the outer torsional flexure hinges 176 continues to occupy corners of the outer reference frame 174.
  • placement of the torsion-bar hinges 182 at the corners of the plate 184 as illustrated in FIG. 19a reduce the size of the torsional scanner 172, it also reduces compounding of the angles when the plate 184 rotates simultaneously about both axes.
  • Compounding increases the distance through which corners of the plate 184 move when the plate 184 simultaneously rotates about axes established by both torsional flexure hinges 176 and torsion-bar hinge 182. Compounding increases the separation required between the plate 184 and the substrate 212 which correspondingly increases the voltage that must be applied between the plate 184 and the electrodes 214 for equivalent performance in rotating the plate 184.
  • the plate 184 has an aspect ratio that is not square as will usually occur for plates 184 included in the reflective switching module 100, then the torsion sensors 192a and 192b in torsional flexure hinges 176 and torsion-bar hinge 182 depicted in FIG. 19a are no longer oriented along orthogonal crystallographic directions, i.e.
  • axes of rotation 236a and 236b established by the torsional flexure hinges 176 and torsion-bar hinge 182 intersect at approximately 70.5°.
  • reorienting the axes of rotation 236a and 236b slightly until they intersect at 90°, as illustrated in FIG. 19b permits the torsional flexure hinges 176 and torsion-bar hinge 182 to be oriented along a single crystallographic direction of silicon, e.g. the ⁇ 100> crystallographic orientation if the outer reference frame 174 is aligned along the ⁇ 110> crystallographic direction of silicon. Configured as illustrated in FIG.
  • the torsional scanner 172 provides a significant amount of space for the inner torsion-bar hinges 182 in the corners of the plate 184 which reduces the size of the torsional scanner 172. Furthermore, the configuration of the torsional scanner 172 illustrated in FIG. 19b preserves the crystallographic orientation of the torsion sensors 192a and 192b while the compounding effect, though not completely eliminated, is significantly reduced. However, in the configuration of the torsional scanner 172 depicted in FIG. 19, the orthogonal axes of rotation established by the torsional flexure hinges 176 and torsion-bar hinge 182 are oriented obliquely to the length and width of the plate 184. Nevertheless, because only small angular rotations of the plate 184 occur during operation of the reflective switching module 100 the area of the plate 184 upon which the beam of light 108 impinges changes insignificantly when the plate 184 rotates.
  • FIG. 20a A preferred arrangement for strips 222' of torsional scanners 172 depicted in FIG. 18a is illustrated in FIG. 20a. As described above and depicted FIG. 20a, the strips 222' are mounted at a 45° angle with respect to a horizontal base 242 of the reflective switching module 100. In the illustration of FIG. 20a, the support frames 224' carrying the strips 222' are also mounted at a 45° angle with respect to the base 242.
  • the two axes established by the torsional flexure hinges 176 and torsion-bar hinge 182 about which the plates 184 rotate are indicated by x and y axes 244 depicted in FIG. 20a.
  • the maximum rotation angles for plates 184 about axes established by the torsional flexure hinges 176 and torsion-bar hinge 182 allowed for identical torsional scanners 172 at the other set 118b or 118a of mirror surfaces 116 establishes a serrated rectangularly-shaped field 246 of addressable torsional scanners 172 in the addressed set 118a or 118b.
  • This optimum rectangularly-shaped field 246 is truncated at the corners and has sides that are approximately diagonal to the strips 222'.
  • the longest strip 222' must include at least 1.4 times more torsional scanners 172 than that required for a rectangular array of the torsional scanners 172 assembled from the strip 222 illustrated in FIG. 16a.
  • torsional scanners 172 may be omitted from locations in the set 118a or 118b that cannot be addressed from the other set 118b or 118a.
  • only a few of the strips 222' illustrated in FIG. 20a need be full length. Those strips 222' that include only a few torsional scanners 172 might even be eliminated entirely.
  • FIG. 20b illustrates an analogous re-arrangement at the sets 118a and 118b of torsional scanners 172 of the type depicted in FIG. 19b.
  • the strips 222" and the support frames 224" are oriented vertically similar to the illustration of FIG. 16a.
  • the x and y axes 244 about which the plate 184 rotate are oriented at 45° with respect to the strips 222" and their support frames 224".
  • the oblique orientation of the x and y axes 244 with respect to the strips 222" and the support frames 224" again means that the maximum rotation angles for plates 184 of corresponding torsional scanners 172 at the other set 118b or 118a of mirror surfaces 116 establishes a serrated octagon or truncated rectangularly-shaped field 256 of addressable torsional scanners 172 at the addressed set 118a or 118b. If the rectangularly-shaped field 256 established for these torsional scanners 172 is p x q, then the optimum field coverage for strips is a square or rectangular field with an area of .7 to 1.2 pq, symmetrically arranged along the diagonal x and y axes 244.
  • FIG. 21 illustrates an arrangement of whereby the collimating lens 112, optical fibers 106 and strips 222 of torsional scanners 172 are brought closer together thereby relaxing tolerances for their alignment.
  • the substrate 212 is made wider than the strip 222 and a mirror strip 262 attached to the surface of the substrate 212 opposite to the strip 222 to establish a beam-folding and deflecting assembly 264.
  • the beam-folding and deflecting assemblies 264 are then arranged into a repeating, regular structure in which the quasi-collimated beam of light 108 reflecting off the mirror strip 262 of one beam-folding and deflecting assembly 264 impinges upon the mirror surface 116 provided by the immediately adjacent torsional scanner 172. Since in the arrangement illustrated in FIG. 21 all the lenses 112 are located an identical short distance from their associated mirror surface 116, alignment of the beams of light 108 to their respective mirror surfaces 116 is less critical.
  • Convergence of the beams of light 108 may be provided in one dimension by tilting each mirror strip 262 slightly from a nominal 45° angle as illustrated schematically in FIG. 21a. Convergence in a second dimension may be obtained by appropriately orienting the optical fiber collimator assemblies 134 with respect to their respective associated mirror surfaces 116 as illustrated schematically in FIG. 21b. Combining these individual one dimensional convergences produces the preferred two dimensional convergence described previously. Orientations for the mirror strips 262 and for the optical fiber collimator assemblies 134 may be chosen to produce the preferred convergence with identical beam-folding and deflecting assemblies 264 that are mounted at slightly different angles with respect to each other. Because in the arrangement illustrated in FIG.
  • the substrates 212 are near their associated mirror surface 116, almost the entire five-hundred (500) to nine-hundred (900) mm long path between the sides 102a and 102b is between pairs of mirror surfaces 116 in the sets 118a and 118b thereby reducing the angles through which the plates 184 must rotate.
  • all electrical connections to the torsional scanners 172 occur at the frontside 169 of the device silicon layer 166, and as illustrated in FIG. 15 the beam of light 108 reflects off a metallic layer coated onto the backside 170 of the device silicon layer 166.
  • the strip 222 is preferably flip-chip bonded to the substrate 212.
  • the substrate 212 may accommodate more than one strip 222 by using a substrate 212 that is larger than the strip 222.
  • the substrate 212 may be fabricated in various different ways.
  • the substrate 212 is fabricated from a ceramic material such as aluminum oxide (alumina) , or, to more closely match the coefficient of thermal expansion of silicon, aluminum nitride.
  • a ceramic material such as aluminum oxide (alumina)
  • electrically conductive vias are laser drilled or punched through ceramic material forming the substrate 212.
  • the substrate 212 may be fabricated from a 100 wafer of silicon. If the substrate 212 is fabricated from a silicon wafer, then cavities 272 may be anisotropically etched into the substrate 212 to provide space for rotation of the plates 184, and to establish a precisely controlled spacing between the plate 184 and electrodes 214 located in the cavities 272. Electrical insulation between leads 228 and between electrodes 214 may be obtained by forming an electrically insulating oxide on the surface of the silicon substrate 212. The electrodes 214 may either be integrated into the silicon substrate 212 or deposited onto the silicon surfaces within each of the cavities 272.
  • the circuits included in a silicon substrate 212 may include current sources for providing an electrical current to the torsion sensors 192a and 192b of the torsional scanners 172, differential amplifiers for receiving signals from the torsion sensors 192a and 192b which indicate the orientation of the inner moving frame 178 and the plate 184, and amplifiers for supplying high voltage signals to the electrodes 214 that energize rotation of the plate 184. Incorporating these various different type of electronic circuits into the substrate 212 significantly reduces the number of leads that must be included in the ribbon cable 226. The number of leads in the ribbon cable 226 may be even further reduced by including one or more multiplexer circuits in the silicon substrate 212.
  • Photo-detectors which respond to a wavelength of light present in the beam of light 108 and which are disposed on the surface of the substrate 212 adjacent to the strip 222 outside shadows cast by the mirror surfaces 116 may be advantageously included on the substrate 212 to detect if a portion of the beam of light 108 misses the mirror surfaces 116.
  • photo- detectors sense if a portion of the beam of light 108 misses the mirror surfaces 116 even if they are covered by portions of the strip 222 other than the mirror surfaces 116 because silicon is transparent to light at wavelengths used for optical fiber telecommunications.
  • the strip 222 is joined to the substrate 212 by electrically-conductive bonds 276 formed in various ways to be described in greater detail below.
  • the electrically-conductive bonds 276 rigidly interconnect pads on the substrate 212 with the pads 194, 198 and 202 of the torsional scanners 172 of the strip 222.
  • the flip-chip bonding of materials forming the strip 222 and the substrate 212 which have closely matched coefficients of thermal expansion introduces a negligible amount of stress thereby keeping the strip 222 flat.
  • the electrically-conductive bonds 276 can be made out of solder, electroplated metal and/or electrically conductive epoxy material.
  • Electrically conductive epoxy provides a compliant connection for the electrically-conductive bonds 276 that absorbs mismatch in coefficients of thermal expansion between the strip 222 and the substrate 212 thus reducing stress on the strip 222.
  • Conductive epoxy material can be screen printed, or dispensed from a syringe. Projecting Au stud bumps or electroplated metal bumps may be formed at appropriate locations on the strip 222 and/or on the substrate 212 in conjunction with electrically conductive epoxy material to provide:
  • the Au stud bumps can be coined to ensure that they have a uniform height, and/or to shape them for increasing mechanical bond strength with the epoxy.
  • Electrically conductive epoxy material usually bonds well to substrates 212 formed using ceramic material such as aluminum oxide or aluminum nitride. However, the electrically conductive epoxy material does not form a similarly strong a bond with the strip 222.
  • the cross-sectional diagram of FIG. 22e illustrates roughening the surface of contact pads on the strip 222 by anisotropically etching truncated pyramidally-shaped troughs 278 into the device silicon layer 166 of the wafer 162.
  • the troughs 278 increases the surface bonding area between the electrically-conductive bonds 276 and contact pads located at the troughs 278 thereby anchoring the electrically-conductive bonds 276 more securely to the strip 222.
  • any gap between peripheries of the strip 222 and the substrate 212 can be eliminated by an underfill 279, illustrated in FIG. 22b.
  • a dam To prevent entry of the underfill material into the cavities 272, a dam must surround them at least until the underfill 279 cures.
  • a compliant underfill 279 such as silicon can be used to absorb a coefficient of thermal expansion mismatch between the substrate 212 and the strip 222 thereby reducing stress on the strip 222.
  • a large number of very small electrically conductive vias 282 may be formed, using a process similar to that described by Calmes, et al. in Transducers 99 at page 1500, through the silicon wafer during fabrication of the substrate 212. Holes for the vias 282 are first formed through the wafer using the standard Bosch deep reactive ion etch ("RIE") process. The holes may be 50 micron wide and 500 micron deep. The wafer is then oxidized thus establishing an electrically insulating oxide layer 284 which isolates the hole from the surrounding wafer.
  • RIE Bosch deep reactive ion etch
  • a highly doped polysilicon layer 286 is grown over the oxide layer 284 by providing a conductive path along the surface of wafer and in the holes. Obtaining a sufficiently conductive polysilicon layer may also require gas phase doping of the polysilicon layer 286 with phosphorus. The conductive polysilicon layer 286 formed in this way electrically connects both sides of wafer. If desired, rings 288 may then be etched through the polysilicon layer 286 around each via 282 thereby electrically isolating the vias 282 from each other. To increase electrical conductivity of substrate 212 and to facilitate forming an electrical contact to the vias 282, one or more additional metal layers may be coated either on one or both sides of the substrate 212 and appropriately patterned.
  • FIG. 22d Mounting of the strip 222 to the substrate 212 that includes the vias 282 is depicted in FIG. 22d. Electrical connections between the strip 222 and vias 282 of the substrate 212 are again formed by electrically-conductive bonds 276.
  • An elastomer layer 292 fastens a polyimide and copper sheet 294 which forms the ribbon cable 226 to the side of the substrate 212 furthest from the strip 222 of torsional scanners 172.
  • Ballgrid or TAB bumps 298 make contact to the conductive vias 282 to establish electrical connections with the polyimide and copper sheet 294. In this way a very large number of contacts to be brought through the substrate 212 with relatively low electrical resistance vias 282.
  • the cavities 272 may be etched thereinto. However, if the substrate 212 is made from a ceramic material or Pyrex then the electrodes 214 must be deposited onto surfaces within the cavities 272. If the strip 222 is fabricated from a flat sheet of material such as ceramic, then as illustrated in FIG. 22f a layer of material providing a spacer 299 must be inserted between the strip 222 and the substrate 212. For substrates 212 lacking etched cavities 272, the spacer 299 establishes a precisely controlled gap between the plates 184 and the electrodes 214 that permits rotation of the plates 184.
  • the spacer 299 may be arranged to also provide a dam that bars entry of the underfill 279 into the cavities 272.
  • the spacer 299 may be made by screen printing material onto the substrate 212 which is subsequently lapped to the appropriate thickness.
  • the spacer 299 is made using either a solder dam material Vacrel® manufactured by E. I. du Pont de Nemours and Company, or a dry film photoresist material that is laminated onto the substrate 212 and photolithographically patterned. Several layers of dry film material of the same or differing thicknesses can be stacked to provide the desired thickness for the spacer 299.
  • the dry film acts as a negative, a sequence of films can be stacked and exposed without development after each lamination thereby assembling a pyramidal-shaped structure.
  • a syringe can be used to dispense conductive epoxy material for the electrically-conductive bonds 276, and the conductive epoxy material need not be cured or b-staged before juxtaposing the substrate 212 with the strip 222.
  • the spacer 299 thus established between the substrate 212 and the strip 222 also mechanically isolates adjacent torsional scanners 172.
  • steep sides 302 formed by 111 planes exposed by anisotropic etching of the handle silicon layer 168 of the wafer 162, illustrated in FIG. 15, prove very advantageous for flip- chip bonding. Not only do the sides 302 substantially protect the mirror surface 116 on the backside 170 of the plate 184 from damage during manufacturing while concurrently mechanically reinforcing the strip 222, but their steep angle scarcely obscures the beam of light 108 impinging upon the mirror surface 116 at an angle of approximately 45°. Furthermore, the mirror surface 116 may be protected from contamination by stretching an extremely thin pellicle 304, similar to those used for integrated circuit ("IC") masks, across the backside of the handle silicon layer 168.
  • IC integrated circuit
  • the flip-chip configuration for mounting the torsional scanner 172 also permits advantageous- ly reducing light scattering as illustrated in FIG. 23.
  • the steep sides 302 and surrounding backside of the handle silicon layer 168 may be coated with an anti reflection layer 312 which effectively absorbs stray light impinging thereon as the beam of light 108 switches between mirror surfaces 116.
  • the steep sides 302 also scatter stray light from the beam of light 108 at very large angles which prevents the side 102a or 102b toward which the beam of light 108 propagates from receiving stray light as the beam of light 108 switches between mirror surfaces 116.
  • FIG. 24 schematically illustrates the reflective switching module 100, such as those illustrated in FIGs. 2, 4a-4b, 5, 6 and 7 as described thus far, encased within an environmental housing 352 that completely encloses the optical path through which the beams of light 108 propagate.
  • the reflective switching module 100 mechanically interconnects the sides 102a and 102b and the sets 118a and 118b and keeps them rigidly aligned.
  • the environmentally sealed environmental housing 352, which protects the reflective switching module 100, may provide temperature regulation thereby maintaining a stable operating environment for the reflective switching module 100.
  • a con- trolled, dry gas, such as nitrogen, may flow through the environmental housing 352 to hinder moisture from condensing within the reflective switching module 100.
  • the environmental housing 352 may also be slightly pressurized to exclude the surrounding atmosphere from the reflective switching module 100.
  • the environmental housing 352 may include a nonsaturable microdryer 353 as described in United States Patent No. 4,528,078 to control the humidity of atmosphere within the reflective switching module 100.
  • a wall 354 of the environmental housing 352 is pierced by electrical feed-throughs 356 for ribbon cables 226.
  • the optical fiber collimator assemblies 134 secured about the ends 104 of the optical fibers 106 plug directly into the convergence blocks 152 which project through the environmental housing 352. In this way, the environmental housing 352 almost hermetically encloses the reflective switching module 100.
  • the ribbon cables 226 are routed carefully to avoid applying stresses to the reflective switching module 100, particularly the support frames 224 and the substrates 212.
  • FIG. 25 illustrates a modular fiber optic switch in accordance with the present invention referred to by the general reference character 400.
  • the fiber optic switch 400 includes a standard twenty-three (23) inch wide telecommunications rack 402 at the base of which is located the environmental housing 352 containing the reflective switching module 100.
  • the environmen- tal housing 352 containing all the torsional scanners 172 rests on a special pedestal on the floor immediately beneath the rack
  • Supporting the environmental housing 352 on the special pedestal minimizes vibration, etc. and thermally couples the environmental housing 352 to the floor to enhance its thermal regulation.
  • duplex sockets 404 included in portcards 406 that are adapted to receive duplex pairs of optical fibers 106.
  • One optical fiber 106 of a duplex pair brings one beam of light 108 to the fiber optic switch 400 and another receives one beam of light 108 from the fiber optic switch 400.
  • the portcards 406 are arranged either horizontally or vertically within the rack 402, and can be individually removed or installed without interfering with immediately adjacent portcards 406. As is a common practice in the telecommunications industry, the portcards 406 are hot swappable.
  • the reflective switching module 100 may contain spare mirror surfaces 116 so the fiber optic switch 400 can retain its full operating capability if a few of the mirror surfaces 116 were to fail.
  • optical fibers 106 connected to a portcard 406 may receive a beam of light 108 therefrom.
  • all or any lesser number of the optical fibers 106 connected to a portcard 406 may carry a beam of light 108 to the portcard 406.
  • the optical fibers 106 may be organized in duplex pairs as illustrated in FIG. 26, but need not be so organized.
  • all items to the left of a dashed line 412 are included in the portcard 406, and all items to the right of a dashed line 414 are included in the reflective switching module 100.
  • the area between the dashed lines 412 and 414 illustrates a backplane of the rack 402.
  • Each portcard 406 includes electronics, alignment optics and electro-optics required to control operation of a portion of the reflective switching module 100.
  • all of the optical fibers 106 included in the reflective switching module 100 connect to a portcard 406.
  • all of the torsional scanners 172 having mirror surfaces 116 upon which any of the beams of light 108 may impinge connect via its substrate 212 and a ribbon cable 226 to a portcard 406.
  • Each portcard 406 preferably, but not necessarily, connects to sixteen (16) or thirty-two (32) optical fibers 106, one-half of which it is envisioned may be receiving a beam of light 108 from the portcard 406 and one-half that may be carrying a beam of light 108 to the portcard 406.
  • sixteen (16) or thirty-two (32) optical fibers 106 one-half of which it is envisioned may be receiving a beam of light 108 from the portcard 406 and one-half that may be carrying a beam of light 108 to the portcard 406.
  • the odd number subscripted optical fibers 106 ⁇ 106 3 , • • • lO ⁇ j-,- ! carry a beam of light 108 to the reflective switching module 100 while the even number subscripted optical fibers 106 2 , 106 4 , • • • 106 2n carry a beam of light 108 from the reflective switching module 100.
  • the portcard 406 includes light sources 422 and taps or directional couplers 424 for supplying and coupling light into the optical fiber 106 for use in servo alignment of the reflective switching module 100.
  • the directional couplers 424 also supply light received from the reflective switching module 100 via optical fibers 106 to light detectors 426.
  • the portcard 406 also includes driving, sensing and control electronics 432, e.g. a digital signal processor ("DSP") together with its associated circuits, which exchange electrical signals via the ribbon cables 226 with the electrodes 214 included in the substrates 212 and with the torsion sensors 192a and 192b included in each of the torsional scanners 172 mounted on the substrates 212.
  • the driving, sensing and control electronics 432 controls the orientation of mirror surfaces 116 including implementing servo loops that ensure their proper orientation, and also communicates with the supervisory processor 436 through an RS232 data communication link 438.
  • the backplane between dashed lines 412 and 414 includes connections for the optical fibers 106 to the portcards 406, preferably multifiber connectors for single mode, optical fiber ribbon cables that connect, for example, 12, 16 or more optical fibers 106.
  • the backplane between dashed lines 412 and 414 also includes connectors 442 for all the ribbon cables 226, the data communication link 438 and other miscellaneous electrical connections such as electrical power required for operation of the driving, sensing and control electronics 432.
  • the two mirror surfaces 116 are initially oriented appropriately using pre-established angular coordinates which specify rotations about two (2) axes for each mirror surface 116 in the pair.
  • the fiber optic switch 400 must store 4xN 2 values for orientation signals produced by the torsion sensors 192a and 192b included in each torsional scanner 172.
  • the reflective switching module 100 includes a look-up table 452, illustrated in FIG. 27a that is maintained in the supervisory processor 436, that stores the 4xN 2 values for orientation signals for use at any time during the operating life of the fiber optic switch 400.
  • the 4xN 2 values for orientation signals produced by the torsion sensors 192a and 192b included in each torsional scanner 172 may be initially determined analytically.
  • the analytically determined coordinates and orientation signals are fine tuned to accommodate manufacturing tolerances, etc.
  • these coordinates and orientation signals may be updated when necessary.
  • the look-up table 452 stores compensation data for initial values of the coordinates and orientation signals, e.g. sensor offsets and temperature compensation since the temperature coefficient of the torsion sensors 192a and 192b is well characterized.
  • a higher frequency servo system uses the orientation signals produced by the torsion sensors 192a and 192b in controlling orientation of each mirror surface 116.
  • the frequency response of this higher frequency servo system permits accurate orientation of pairs of mirror surfaces 116 when switching from one pairing of optical fibers 106 to another pairing.
  • the higher frequency servo system also maintains orientation of all mirror surfaces 116 despite mechanical shock and vibration.
  • the fiber optic switch 400 also employs lower frequency optical feedback servo described in greater detail below.
  • orientation signals are transmitted from the look-up table 452 respectively to two dual axis servos 454 that are included in the portcards 406 for each torsional scanner 172 which exchanges signals with the portcard 406.
  • Each dual axis servo 454 transmits driving signals via the ribbon cable 226 to the electrodes 214 included in the substrates 212 to rotate the mirror surfaces 116 to pre-established orienta- tions.
  • the two torsion sensors 192a and 192b included in each torsional scanner 172 transmit their respective orientation signals back to the respective dual axis servos 454 via the ribbon cable 226.
  • the dual axis servos 454 respectively compare the orientation signals received from their associated torsion sensors 192a and 192b with the values for orientation signals received from the look-up table 452. If any difference exists between the stored values for orientation signals received from the look-up table 452 and the orientation signals which the dual axis servos 454 receive from their respective torsion sensors 192a and 192b, then the dual axis servos 454 appropriately correct the driving signals which they transmit to the electrodes 214 to reduce any such difference.
  • FIG. 27b depicts one of two identical channels, either x-axis or y-axis, of the dual axis servos 454.
  • a current source 462 included in the portcard 406 supplies an electric current to the series connected torsion sensors 192a and 192b of the torsional scanner 172.
  • Differential output signals from one or the other of the torsion sensors 192a and 192b, in the illustration of FIG. 27 the X-axis torsion sensor 192b are supplied in parallel via the ribbon cable 226 to inputs of an instrumentation amplifier 463 also included in the portcard 406.
  • the instrumentation amplifier 463 transmits an output signal that is proportional to the signal produced by the X-axis torsion sensor 192b to an input of an error amplifier 464.
  • the driving, sensing and control electronics 432 of the portcard 406 includes a DSP 465 which executes a computer program stored in a random access memory (“RAM") 466. Also stored in the RAM 466 are values for orientation signals which specify an orientation for the mirror surface 116 that have been supplied from the look-up table 452 maintained at the supervisory processor 436.
  • the computer program executed by the DSP 465 retrieves the angular coordinate, either X-axis or Y-axis as appropriate, and transmits it to a digital-to-analog converter (DAC) 467.
  • the DAC 467 converts the angular coordinate received from the DSP 465 in the form of digital data into an analog signal which the DAC 467 transmits to an input of the error amplifier 464.
  • An output of the error amplifier 464 transmits a signal to an input of an integrator circuit 472 that is proportional to the difference between the analog signal representing the angular coordinate and the signal from the instrumentation amplifier 463 that is proportional to the signal produced by the X-axis torsion sensor 192b.
  • the integrator circuit 472 consisting of an amplifier 473 and a network of resistors 474 and capacitors 475, transmits an output signal directly to an input of a summing amplifier 476a, and to an input of an inverting amplifier 477.
  • the inverting amplifier 477 transmits an output signal to an input of a second summing amplifier 476b.
  • inputs of the summing amplifiers 476a and 476b also receive a fixed bias voltage.
  • the summing amplifiers 476a and 476b respectively transmit output signals, which are proportional to a sum of their respective input signals, to inputs of a pair of high voltage amplifiers 478a and
  • the high voltage amplifiers 478a and 478b respectively transmit driving signals via the ribbon cable 226 either to the
  • the dual axis servos 454 supply differential drive signals to the electrodes 214 of the torsional scanner 172 which respectively are symmetrically greater than and less than a voltage established by the bias voltage supplied to the summing amplifiers 476a and 476b. Furthermore, the drive signals which the dual axis servos 454 supply to the electrodes 214 are appropriately corrected to reduce any difference that might exist between the output signals from the torsion sensors 192a and 192b and the values for orientation signals specified in the look-up table 452.
  • each portcard 406 included in the fiber optic switch 400 includes one directional coupler 424 for each optical fiber 106 together with one light detector 426.
  • Each directional coupler 424 couples approximately 5% to 10% of light propagating through one optical fiber included in the directional coupler 424 into another optical fiber with 95% to 90% of that light remaining in the original optical fiber.
  • a light source 422 is turned-on 5% to 10% of the light emitted by the light source 422 into the directional coupler 424 passes into an incoming optical fiber 106, e.g. optical fiber 106 ! , for transmission onto the reflective switching module 100 together with 95% to 90% of any other light that is already propagating along the optical fiber 106 toward the reflective switching module 100.
  • the reflective switching module 100 couples this combined light from the incoming optical fiber 106, e.g. optical fiber 106 ⁇ into an outgoing optical fiber 106, e.g. optical fiber 106 2 .
  • the directional coupler 424 associated with the outgoing optical fiber 106 e.g.
  • optical fiber 106 2 5% to 10% of the light received from the reflective switching module 100 passes from the optical fiber 106 through the directional coupler 424 to the light detector 426 connected to that directional coupler 424. If necessary, the fiber optic switch 400 exploits the ability to introduce light into the optical fiber 106 for transmission through the reflective switching module 100 and then recovering a fraction of the transmitted light to analyze and adjust the initial operating state of specific pairs of mirror surfaces 116.
  • the optical servo aligns a pair of mirror surfaces 116 regardless of the direction in which alignment light propagates through the pair of mirror surfaces 116, i.e. from incoming optical fiber 106 to outgoing optical fiber 106 or conversely. Consequently, in principle the portcards 406 need equip only one-half of the optical fibers 106 included in the fiber optic switch 400, e.g. all the incoming optical fibers 106 or all the outgoing optical fibers 106, with the light source 422.
  • all of the directional couplers 424 both those connected to incoming and to outgoing optical fibers 106, may, in fact, be equipped with the light source 422.
  • the fiber optic switch 400 When initially aligning pairs of mirror surfaces 116, if the the fiber optic switch 400 detects sufficient light propagating along an incoming optical fiber 106, it will use the incoming light for alignment. However, if there is insufficient light propagating along the incoming optical fiber 106, then light from the light source 422 coupled into the optical fiber 106 is intensity modulated at a very low frequency, e.g. turned on and off, and the signal produced by light detectors 426 analyzed to detect the presence of the modulation on outgoing optical fibers 106. If light from the light source 422 is used for alignment, the portcard 406 through which the outgoing optical fiber 106 passes prevents the intensity modulated light from leaving the fiber optic switch 400.
  • a very low frequency e.g. turned on and off
  • the light on the outgoing optical fiber 106 may be kept within the fiber optic switch 400 by including a 1x2 switch at the output of the portcard 406 and directing the modulated light generated by the light source 422 to a dead-ended optical fiber.
  • the reflective switching module 100 can concurrently perform initial alignment of many different pairs of mirror surfaces 116 coupling beams of light 108 between pairs of ends 104, and may verify the existence of a specified correct connection.
  • an output from every directional coupler 424 of the portcard 406 supplies light to a telecom-signal-strength photo-detector 482.
  • Every telecom-signal-strength photo-detector 482 receives and responds to a fraction of light propagating into the reflective switching module 100 along the optical fibers 106 regardless of whether the optical fiber 106 is an incoming or an outgoing optical fiber 106.
  • output signals from two telecom-signal-strength photo-detectors 482 indicate whether portcard 406 must supply light from the light source 422 for precisely aligning the mirror surfaces 116 or whether the incoming optical fiber 106 carries a telecommunication signal of sufficient strength to permit precise optical alignment. If the signals from the pair of telecom-signal-strength photo-detectors 482 indicate that neither of two optical fibers 106 carry sufficient light to perform precise optical alignment, then the portcard 406 turns-on the light source 422 to obtain the required light, otherwise light present on an incoming optical fiber 106 is used for that purpose.
  • One approach for using light introduced into the optical fiber 106 from the light source 422 illustrated in FIG. 26a envisions using 850 nm light from a relatively inexpensive laser diode for the light source 422.
  • an alignment-light detector 484 that is sensitive to red wavelengths of light may be an inexpensive silicon photo-detector.
  • the incoming optical fiber 106 may also be concurrently carrying light at optical telecommunication wavelengths, e.g. 1310 A° or 1550 A°, which perhaps has greater power than that generated by the light source 422.
  • the output of the directional coupler 424 which emits a portion of the light received by the portcard 406 from the reflective switching module 100 directs such light onto a dichroic mirror 486 2;
  • the dichroic mirror 486 23 reflects the 850 nm alignment light to the alignment-light detector 484 while permitting light at optical telecommunication wavelengths to pass onto a telecom-signal-monitoring photo-detector 488.
  • any optical fiber 106 may at any instant be an incoming or an outgoing optical fiber 106, then a dichroic mirror 486 2j - a must be used with the directional coupler 424 2j _ ⁇ to separate light from the light source 422 ⁇ .. from light at optical telecommunication wavelengths that the telecom-signal-monitoring photo-detector 488 2J . receives.
  • the telecom-signal-strength photo-detector 482 which first receives light at optical telecommunication wavelengths coming into the fiber optic switch 400 via the duplex sockets 404 detects loss of light or loss of modulation in incoming light.
  • the telecom-signal-monitoring photo-detectors 488 are used in conjunction with the telecom-signal-strength photo-detectors 482 for periodically monitoring and maintaining the quality of light transmission through the reflective switching module 100.
  • Tests have demonstrated that the orientation signals from the torsion sensors 192a and 192b supplied to the dual axis servo 454 maintain adequate alignment of the mirror surfaces 116 for extended period of time, e.g. hours.
  • the dichroic mirror 486 2j and its associated photo-detectors 484 and 488 may be replaced by a compound sandwich photo-detector, illustrated in FIG. 26b.
  • a silicon photo-detector 492 is mounted over a long wavelength photo-detector 494 such as germanium (Ge) or indium gallium arsenide (InGaAs) photo-detector.
  • the compound sandwich photo- detector absorbs the shorter alignment wavelength in the silicon photo-detector 492.
  • the directional couplers 424 become multi-mode devices so the fraction of the alignment light being coupled into and out of the optical fiber 106 varies over time.
  • optical telecommunication wavelengths e.g. 1310 A° or 1550 A°
  • Light at these wavelengths may be provided by an inexpensive vcsel. While vcsels lack the precise wavelength or stability of expensive laser sources of such light, the precision and stability provided by laser sources are not required for optically aligning a pair of mirror surfaces 116.
  • Using light at optical telecommunication wavelengths has the advantage that the and the alignment-light detector 484 may be eliminated, and that the coupling coefficient for the directional couplers 424 are higher and more stable than for 850 nm light.
  • a vcsel need supply less light or power for optical alignment than a laser diode producing 850 nm light. Because every optical fiber 106 passes through a portcard 406, a significant portion of the manufacturing cost of the fiber optic switch 400 is the cost of the portcards 406. Thus, it is economically advantageous to reduce, as much as practicable, the manufacturing cost for portcards 406. Thus, if initial optical alignment of pairs of mirror surfaces 116 requires using an expensive laser that generates light at optical telecommunication wavelengths for the light source 422, the cost of that source may be shared among directional couplers 424 using a lxN optical switch. Such a lxN optical switch may be very large to provide light to all the portcards 406. Alternatively, to enhance reliability the fiber optic switch 400 might include several such optical telecommunication lasers with a smaller lxN optical switches each one of which provides light to only the directional couplers 424 included in a single portcard 406.
  • FIGs. 26c and 26d illustrate using lower cost, bent-fiber taps 495 for injecting light into or extracting light from the optical fibers 106 as is commonly done when fusing optical fibers.
  • each incoming optical fiber 106 2; l bends around a sufficiently small, grooved mandrel 496 so light radiates from the optical fiber 106 2 _-. 1 as is well known in the art.
  • This technique also permits injecting light emitted from the light source 422 into the core or cladding of the optical fiber 106 2;) _ 1 although that is less desirable because the cladding permits multi-mode light propagation.
  • Light propagating in the core of the optical fiber lO ⁇ then becomes the beam of light 108 that is directed by a pair of mirror surfaces 116 to the output optical fiber 106 2j .
  • Each outgoing optical fiber 106 2;] also bends around a mandrel 496 so light radiating from the optical fiber 106 2D strikes the light detector 426 2D .
  • the light detector 426 2 _ may have two (2) sections 426a and 426b, one section 426a for monitoring alignment light, and one section 426b for monitoring light at optical communication wavelengths.
  • the light detector 426 2; may be of the type illustrated in FIG. 26b and described previously in which the sections 426a and 426b overlay each other.
  • the telecom-signal-strength photo-detector 4S2 2 ⁇ monitors loss and loss of modulation of optical communication light propagating into the reflective switching module 100 along the input optical fiber 106 2J - !
  • the section 426b 2j monitors light that passes through the reflective switching module 100 at optical communication wavelengths.
  • the telecom-signal-strength photo-detector 482 2j and light detector 426 ⁇ .. ! serve the corresponding functions for bidirectional duplex optical fibers 106. If alignment light has the same wavelength as optical communication light, then using tandem detection is unnecessary.
  • the same light source 422 may inject light into several optical fibers 106 simultaneously.
  • Alignment light may be coupled into the cladding or into the core of the optical fiber 106 2j _ ⁇ . If coupled into the cladding, the alignment light may be removed from the optical fiber 106 2j by an absorber 497 located along the output optical fiber 106 2j past the mandrel 496. This then allows continuous use of virtually any wavelength of light for aligning the mirror surfaces 116, since no alignment light propagates beyond the portcard 406.
  • the bent-fiber tap 495 may be employed for all optical fibers 106, both incoming and outgoing of the portcard 406.
  • FIG. 27b illustrates a circuit for sharing a single channel of one dual axis servo 454 among several different pairs of electrodes 214.
  • the output signal from the high voltage amplifiers 478a and 478b are supplied respectively to inputs of high-voltage multiplexers 512a and 512b.
  • Other inputs of the high-voltage multiplexers 512a and 512b receive digital selection signals sent from the DSP 465 via a set of digital control lines 514.
  • Output signal lines from the high-voltage multiplexers 512a and 512b connect respectively to individual electrodes 214, for example all the electrodes 214 that connect to a single portcard 406.
  • the digital selection signals supplied to the high-voltage multiplexers 512a and 512b specify to which of several pairs of electrodes 214 the voltages present at the outputs of the high voltage amplifiers 478a and 478b are respectively applied by the high-voltage multiplexers 512a and 512b.
  • the DSP 465 transmits data specifying the appropriate output voltages to the DAC 467.
  • the high voltage amplifiers 478a and 478b then produce appropriate driving voltages for the selected pair of electrodes 214 while the high-voltage multiplexers 512a and 512b couple that voltage to electrodes 214 selected.
  • the digital computer program executed by the DSP 465 may select pairs of electrodes 214 in a sequence that minimizes the change in voltage which the high voltage amplifiers 478a and 478b must supply to successive pairs of electrodes 214 thereby reducing the slewing requirement of the high voltage amplifiers 478a and 478b.
  • step-up transformers simplify the circuit which applies the driving signal to the electrodes 214 because the primary of the transformer receives a much lower voltage that is more compatible with semiconductor devices thereby eliminating any need for high voltage components.
  • FIG. 27d depicts a circuit for applying an AC voltage to the electrodes 214 of a torsional scanner 172 to induce rotation both of the plate 184 and of the inner moving frame 178.
  • the circuit illustrated in FIG. 27d includes three (3) high-frequency transformers 522, 524 and 526 each of which preferably has a ferrite core.
  • An oscillator 528 supplies a low AC voltage, e.g. 10 volts peak-to-peak ("P-P") , to a primary winding 532 of the transformer 522 at a high frequency, i.e. significantly higher than the mechanical resonant frequency of the plate 184.
  • P-P peak-to-peak
  • the transformer 522 increases the AC voltage received from the oscillator 528 twenty (20) times to approximately 200 volts P-P at an secondary winding 534 of the transformer 522.
  • the secondary winding 534 of the transformer 522 connects respective- ly to center taps of secondary windings 536a and 536b of the transformers 524 and 526.
  • Opposite terminals of the secondary winding 536a of the transformer 524 connect to the electrodes 214a and 214b that are juxtaposed with the plate 184.
  • opposite terminals of the secondary winding 536b of the trans- former 526 connect to the electrodes 214a and 214b that are juxtaposed with the inner moving frame 178.
  • the low AC voltage supplied to the primary winding 532 of the transformer 522 is also applied directly, and through an inverting amplifier 538, to inputs of multiplying DACs 542a and 542b. Similar to the DAC 467 depicted in FIG. 27b, other inputs to the multiplying DACs 542a and 542b receive angular coordinate data for the plate 184 and for the inner moving frame 178 directly from the DSP 465. Outputs of the multiplying DACs 542a and 542b connect respectively to primary windings 544a and 544b of the transformers 524 and 526.
  • the multiplying DACs 542a and 542b can apply adjustable AC voltages to the primary windings 544a and 544b of the transformers 524 and 526 that are either in-phase or out-of-phase with the AC voltage applied to the primary winding 532 of the transformer 522.
  • the transformers 524 and 526 both increase the AC voltage received respectively from the multiplying DACs 542a and 542b forty (40) times to approximately 400 volts P-P across the secondary windings 536a and 536b.
  • FIG. 27e illustrates waveforms at the secondary winding 534 of the transformer 522 and respectively at the electrodes 214a and 214b that are juxtaposed with the plate 184 when, responsive to data received from the DSP 465, the multiplying DAC 542a applies an AC voltage across the transformer 524 in-phase with the voltage applied to the primary winding 532 of the transformer 522.
  • the electrostatic force between the plate 184 and a pair of electrodes 214 is independent of the sign of the applied voltage, for the waveforms depicted in FIB. 27e the forces applied to the plate 184 respectively by the electrodes 214a and 214b differ.
  • the multiplying DACs 542a and 542b apply unequal, in-phase AC voltages across the primary windings 544a and 544b of the transformers 524 and 526 responsive to data received from the DSP 465, such data may also cause the multiplying DACs 542a and 542b to apply voltages that are out-of- phase across the primary windings 544a and 544b as indicated in FIG. 27f.
  • the net result of applying the voltages such as those illustrated either in FIGs. 27e or in 27f to the electrodes 214 is that the plate 184 tilts closer to one of the electrodes 214a or 214b and away from the other electrode 214b or 214a.
  • the inertia of the plate 184 smooths and evens out the effect of intermittent force applied at twice the frequency of the AC voltage produced by the oscillator 528. If the frequency of the AC voltage generated by the oscillator 528 is sufficiently low, then the resulting small oscillation of the plate 184 may be used for phase sensitive detection of signals for precisely aligning the beam of light 108.
  • Unequal forces may also be applied to the plate 184 by the electrodes 214a and 214b by varying the phase relationship between a constant amplitude AC voltage applied to the transformer 524 and that applied to the transformer 522, rather than by varying the AC voltage applied to the transformer 524.
  • Operation of the multiplying DAC 542b and the transformer 526 to effect rotation of the inner moving frame 178 is identical to that described above for the plate 184.
  • the dual axis servo 454 depicted in FIG. 27b applies symmetric DC voltages to pairs of electrodes 214 to induce rotation of the plate 184 with the voltage on one electrode 214 increasing and the other decreasing by equal amounts.
  • Such drive voltages balance any capacitive coupling to the signals from the torsion sensors 192a and 192b because they are usually exposed symmetrically to the voltages applied to pairs of the electrodes 214.
  • the long output lines from the torsion sensors 192a and 192b are arranged so that they are exposed equally to positive and negative voltage swings.
  • Techniques to balance the exposure of these signal lines to drive signals supplied to the electrodes 214 may include inserting additional lines in connectors and/or leads, and applying voltages so that each sensor line is fully symmetrically exposed to both voltage swings.
  • shielded lines may be used for signals from the torsion sensors 192a and 192b, and the drive signal lines to the electrodes 214 placed closely together to avoid inductive and capacitive coupling.
  • Including the fiber optic switch 400 in a telecommunications network makes reliability and availability of utmost importance. Therefore, it is extremely important that the mirror surfaces 116 are always under control of the dual axis servos 454, that initially forming a connection which couples light from one optical fiber 106 to another optical fiber 106 via the reflective switching module 100 be precise, and that the quality of the coupling be maintained while the connection persists. As described above in connection with FIGs. 26 and 26a, all the portcards 406 provide a capability for monitoring the precise alignment of pairs of mirror surfaces 116 either with light incoming to the fiber optic switch 400 or with light generated by one of the light sources 422.
  • the fiber optic switch 400 exploits the capability of the portcards 406 to facilitate optical alignment of pairs of mirror surfaces 116 by monitoring the quality of coupling between pairs of optical fibers 106 connected to the reflective switching module 100. In monitoring the quality of that coupling, the fiber optic switch 400 tilts slightly each mirror surface 116 in a pair from the orientation specified by the values for orienta- tion signals stored in the look-up table 452, i.e. dithering both mirror surfaces 116, while concurrently monitoring the strength of the beam of light 108 coupled between the two optical fibers 106.
  • the commands sent by the supervisory processor 436 cause the DSP 465 to send coordinate data to the two DACs 467 included in the dual axis servo 454 which tilts slightly the mirror surface 116 whose orientation the dual axis servo 454 controls. Because this change in orientation changes the impingement of the beam of light 108 on the lens 112 associated with the outgoing optical fiber 106, the amount of light coupled into the associated optical fiber 106 changes. This change in the light coupled into the optical fiber 106 is coupled through the directional coupler 424 through which the outgoing light passes to the light detector 426 included in that portcard 406.
  • the computer program executed by the DSP 465 acquires light intensity data from an analog-to-digital converter ("ADC") 504 that is coupled to the light detector 426 as illustrated in FIG. 27b.
  • ADC analog-to-digital converter
  • the fiber optic switch 400 either in the DSP 465 on the portcard 406 or in the supervisory processor 436, or in both, analyzes this light intensity data to precisely align the two mirror surfaces 116 for coupling the beam of light 108 between the two optical fibers 106.
  • the fiber optic switch 400 confirms that light from the incoming optical fiber 106 is being coupled through the reflective switching module 100 to the proper outgoing optical fiber 106 by dithering only the mirror surface 116 upon which the incoming beam of light 108 first impinges. If the reflective switching module 100 has been properly aligned to couple light between a specified pair of optical fibers 106, the intensity modulation of light from the incoming beam of light 108 caused by dithering this particular mirror surface 116 must appear in only the correct outgoing optical fiber 106, and in no other optical fiber 106.
  • the fiber optic switch 400 After the pair of mirror surfaces 116 have been optically aligned as described above, and after confirming that incoming light is being coupled through the reflective switching module 100 into the proper optical fiber 106, the fiber optic switch 400 periodically monitors the quality of the connection using the ability to dither the orientation of the mirror surfaces 116.
  • the computer program executed by the supervisory processor 436 as appropriate uses the alignment data acquired in this way for updating the angular coordinate data stored in the look-up table 452, and may also preserve a log of such data thereby permitting long term reliability analysis of fiber optic switch 400.
  • FIG. 28a shows an alternative embodiment structure for receiving and fixing optical fibers 106 that may be used at the sides 102a and 102b instead of the convergence block 152 and the optical fiber collimator assemblies 134.
  • a clamping plate 602 micromachined from silicon, secures the optical fibers 106.
  • An adjustment plate 604 also micromachined from silicon, permits adjusting the ends 104 of the optical fibers 106 that protrude therethrough both from side-to-side and up-and-down, and then fixing the ends 104 in their adjusted position.
  • the clamping plate 602 is pierced by an array of holes 606 which are etched through a 1.0 to 2.0 mm thick silicon substrate using the Bosch deep RIE process.
  • the hole 606 positions the optical fibers 106 precisely with respect to each other within a few microns.
  • a pyramidally shaped entrance 608 to the holes 606, only one of which is illustrated in FIG. 28a, may be formed on one side of the clamping plate 602 using anisotropic etching. While the holes 606 may be formed as right circular cylinders, they may also have more complicated cylindrical profiles such as that illustrated in FIG. 28b.
  • the holes 606 may be RIE or wet etched to provide a profile in which a cantilever 612 projects into the hole 606.
  • the cantilever 612 is positioned with respect to the remainder of the hole 606 so that insertion of the optical fiber 106 thereinto bends the cantilever 612 slightly. In this way the cantilever 612 holds the optical fiber 106 firmly against the wall of the hole 606 while permitting the optical fiber 106 to slide along the length of the hole 606.
  • the holes 606 may incorporate other more complicated structures for fixing the optical fiber 106 with respect to the holes 606.
  • a portion of each hole 606 may be formed with the profile depicted in FIG. 28b while the remainder, etched in registration from the opposite side of the clamping plate 602, may be shaped as a right circular cylinder.
  • optical fibers 106 are inserted through all the holes 606 until all the optical fibers 106 protrude equally a few millimeters, e.g. 0.5 to 3.0 mm, out of the clamping plate 602. Protrusion of the optical fibers 106 this far beyond the clamping plate 602 permits easily bending them. Identical protrusion of all the optical fibers 106 may be ensured during assembly by pressing the ends 104 of the optical fibers 106 against a stop. The optical fibers 106 may be fixed to the clamping plate 602 by gluing, soldering, or simply be held by frictional engagement with the cantilever 612.
  • the adjustment plate 604 includes an array of XY micro-stage stages 622 also etched through a 1.0 to 2.0 mm thick silicon substrate using the Bosch deep RIE process.
  • Each XY micro-stage 622 includes a hole 624 adapted to receive the end 104 of the optical fiber 106 that projects through the clamping plate 602.
  • the distances between holes 624 piercing the adjustment plate 604 are identical to those which pierce the clamping plate 602, and may be formed with the profile depicted in FIG. 28b.
  • Each optical fiber 106 fits snugly within the hole 624.
  • FIG. 29 a depicts in greater detail one of the XY micro-stage stages 622 included in the adjustment plate 604.
  • An analogous monolithic silicon XY stage is described in United States Patent no. 5,861,549 ("the '549 patent") that issued January 19, 1999.
  • FIG 29a illustrates that the entire XY micro-stage 622 is formed monolithically from a silicon substrate using RIE etching.
  • An outer base 632, that encircles the XY micro-stage 622, is coupled to an intermediate Y-axis stage 634 by four (4) flexures 636 of a type described by Teague, et al. in, Rev. SCI. Instrum. , 59, pg. 67, 1988.
  • flexures 642 couple the Y-axis stage 634 to a X-axis stage 644.
  • the flexures 636 and 642 are of the paraflex type and therefore stretch adequately for the XY motion envisioned for the hole 624.
  • the XY micro-stage 622 need only to be able to move and position the ends 104 of the optical fibers 106 over small distances which avoids undue stress on the flexures 636 and 642.
  • Other configu- rations for the flexures 636 and 642 similar to those described in the '549 patent, may also be used.
  • the XY micro-stage 622 likely omits any actuators, but the Y-axis stage 634 may be fixed in relation to the outer base 632 with a metal ribbon, e.g. gold, kovar, tungsten, molybdenum, aluminum, or wire linkage 652. Similarly, the X-axis stage 644 may be fixed in relation to the Y-axis stage 634 also with a metal ribbon or wire linkage 654.
  • the material chosen for the linkages 652 and 654 preferably has a coefficient of expansion the same as or close to that of silicon. However, if the linkages 652 and 654 are short, e.g. 100 microns, then even for a 20 PPM differential coefficient of expansion between the silicon and the metal (e.g. aluminum) , the movement of the X-axis stage 644 with respect to the outer base 632 would only be approximately 20 A° per degree Celsius. Metals other than aluminum provide even greater thermal stability.
  • the linkages 652 and 654 are first bonded respectively to the Y-axis stage 634 and to the X-axis stage 644.
  • the X-axis stage 644 may be moved along both the X and Y axes to position the end 104 at a specified location. After the X-axis stage 644 has been move to properly position the end 104, the linkages 652 and 654 are bonded or spotwelded in place.
  • the XY micro-stage 622 may include a lever 622 illustrated in FIG. 29c to reduce movement of the X-axis stage 644 in comparison with movement of a distal end 664 of the XY micro-stage 622.
  • etching to form the stages 634 and 644 also yields the lever 622 that is cantilevered from the Y-axis stage 634.
  • the linkage 654 is initially bonded both to the X-axis stage 644 and to the lever 622.
  • a similar linkage 666 is fastened to the end of the lever 622 distal from its juncture with the Y-axis stage 634.
  • the linkage 654 may be omitted from the XY micro-stage 622 to be replaced by a flexible pushpin 672, well known in the art, that couples between the X-axis stage 644 and the lever 622 cantilevered from the Y-axis stage 634.
  • a flexible pushpin 672 well known in the art, that couples between the X-axis stage 644 and the lever 622 cantilevered from the Y-axis stage 634.
  • Opposite ends of the flexible pushpin 672 are coupled by flexures 674 respectively to the X-axis stage 644 and to the lever 622.
  • 29c requires only one linkage 666 for fixing the X-axis stage 644 when the end 104 of the optical fiber 106 is at its specified location. Furthermore, the movement of the X-axis stage 644 is now bi-directional because the flexible pushpin 672 can both push and pull on the X-axis stage 644.
  • lever 622 has addressed only X-axis motion of the X-axis stage 644, it is readily apparent that a similar lever could be incorporated into the outer base 632 for effecting Y-axis motion of the Y-axis stage 634 and of the X-axis stage 644 with respect to the outer base 632.
  • the XY micro-stage 622 permits fixing and adjusting the ends 104 of optical fibers 106 along their X and Y axes.
  • properly focusing the lens 112 with respect to the ends 104 of optical fibers 106 may require relative movement either of the end 104 or the lens 112 along the longitudinal axis 144.
  • the separation between the end 104 of optical fiber 106 and the lens 112 may be adjusted in various different ways.
  • Bright, et al., SPIE Proc, vol. 2687, pg.34 describe a poly-silicon mirror, moving like a piston, which may be electrostatically displaced perpendicular to the substrate upon which it has been fabricated.
  • FIG. 30a depicts a monolithic plano-convex lens 112 micromachined from a SOI wafer 162 using RIE etching that can be electrostatically displaced along the longitudinal axis 144 perpendicular to the substrate upon which it was been fabricated.
  • the lens 112 is supported from the surrounding device silicon layer 166 of the wafer 162 by three (3) V-shaped flexures 682.
  • One end of the flexures 682 each of which extends part way around the periphery of the lens 112, is coupled to the surrounding device silicon layer 166 while the other end is coupled to the lens 112.
  • the entire assembly is made as one monolithic silicon structure. Electrostatic attraction between the electrodes 684 and the combined flexures 682 and the lens 112, created by applying an electrical potential between the electrodes 684 and the device silicon layer 166, pulls the lens 112 toward the electrodes 684 along the longitudinal axis 144.
  • Silicon lenses suitable for IR optical fiber transmission are commercially available and may be adapted for use in this invention. Accordingly, small individual commercially available micro-lenses may be placed into a cavity etched into a flat membrane supported by the flexures 682. Alternatively, the lens 112 may be formed using RIE while the flexures 682 are being formed. Yet another alternative is to first diamond turn the lens 112 and then protect it from etching while the flexures 682 are formed using RIE. Still another alternative is to first form the flexures 682 using RIE while protecting the area where the lens 112 is to be formed, and then diamond turning the lens 112.
  • the wafer 162 underlying them is removed with anisotropic etching to expose the silicon dioxide layer 164.
  • the backside 170 of the lens 112 fabricated in this way is optically flat.
  • the lens 112 may be moved along the longitudinal axis 144 electro-magnetically. As illustrated in FIG. 30c, the electrodes 684 disposed adjacent to the lens 112 in the illustration of FIG. 30a are replaced with permanent magnets 692 oriented with their magnetic field parallel to the longitudinal axis 144 of the lens 112. Also a coil 694 encircles the lens 112. Electrical leads from the coil 694 are brought out to the device silicon layer 166, preferably symmetri- cally, via the flexures 682 to ensure linear displacement of the lens 112. Depending upon the direction of current flow applied to the coil 694, the lens 112 moves toward or away from the end 104 of the optical fiber 106.
  • FIGs. 31a and 31b depicts several magnets 696 all oriented in the same direction along a strip of torsional scanners 172.
  • the torsional scanners 172 also include coils 698 disposed on the inner moving frame 178 thereof through which an electric current flows when effecting rotation of the plate 184.
  • the torsional scanners 172 permits removing from the substrate 212 the electrodes 214 that are juxtaposed with the inner moving frame 178.
  • the substrate 212 will include cavities adjacent to the inner moving frame 178, as described in United States Patent No. 6,044,705 that issued April 4, 2000. Such cavities permit large rotations of the inner moving frame 178 about the axis estab- lished by the torsional flexure hinges 176.
  • the magnets 696 typically have a trapezoidal cross- section which allows the beam of light 108 to impinge upon the mirror surface 116 at a large angle.
  • the magnets 696 may be arranged linearly along opposite sides of the torsional scanners 172. This configuration for the torsional scanners 172 and the magnets 696 provides better demagnetization factor for the magnets and stronger fields.
  • FIG. 32 illustrates an arrangement in which a routing wavelength demultiplexer 702 includes several demultiplexed planar waveguides 704.
  • the demultiplexed planar waveguides 704 radiate beams of light 108 directly toward the lenses 112 facing them thereby avoiding any necessity for coupling the routing wavelength demultiplexer 702 to optical fibers.
  • a substrate 706 of the routing wavelength demultiplexer 702, which carries demultiplexed planar waveguides 704, may be placed adjacent to the lenses 112 to supply incoming beams of light 108 to the reflective switching module 100.
  • the lenses 112 may couple the beams of light 108 directly to demultiplexed planar waveguides 704 from which the beams of light may be multiplexed into one or several outgoing optical fibers.
  • the fiber optic switch 400 may provide wavelength conversion for light received from any optical fiber coupled to the fiber optic switch 400. Wavelength conversion is desirable in many applications for the fiber optic switch 400. Wavelength conversion may be readily achieved by forming a grating 712 on the plate 184 of a torsional scanner 172 as illustrated in FIGs. 33a and 33b. A laser diode 714 together with a lens 716 and the grating 712 form a Littrow cavity similar to those described in United States Patents Nos. 5,026,131, 5,278,687 and 5,771,252.
  • the grating 712 carried on the rotatable plate 184 reflects the first order diffracted beam back to the laser diode 714 thereby establishing, with a rear facet of the laser diode 714, an optical cavity for lasing.
  • a beam splitter 722 directs a zeroth order diffracted output beam 724 to a wavelength locker 726 as is well known in the art.
  • rotation of the plate 184 carrying the grating 712 varies the wavelength of light in the output beam 724.
  • Feedback from the wavelength locker 726 may be used to control rotation of the plate 184 thereby selecting a specific wavelength for the output beam 724.
  • FIG. 33b illustrates using the Littrow cavity in converting light in an incoming beam 732 to an arbitrarily selected wavelength.
  • the incoming beam 732 impinges upon a gain medium 734 that is excited by the laser diode 714 to a level just below a threshold for lasing.
  • the incoming beam 732 at a first wavelength raises the gain medium 734 above the threshold for lasing thereby causing lasing at a wavelength selected by the orientation of the plate 184 that carries the grating 712.
  • the wavelength locker 726 provides feedback for selecting a specific wavelength for the output beam 724.
  • the structure of the grating 712 carried on the plate 184 is used for measuring wavelength of light propagating along the optical fiber 106.
  • the light detector 744 may be physically very small and therefore quite inexpensive. In comparison, diode arrays that respond well to infrared radiation are comparatively expensive.

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  • Optical Couplings Of Light Guides (AREA)

Abstract

Cette invention a trait à un commutateur à fibres optiques (400) comprenant un module de commutation (100) à fibres optiques qui reçoit et fixe des extrémités (104) de fibres optiques (106). Le module (100) comprend de nombreux déflecteurs (172) de rayons lumineux de réflexion, agencés en forme de V, qui peuvent être choisis par paires afin de coupler un rayon lumineux (108) entre deux fibres optiques (106). Le module (100) permet aussi de produire des signaux d'orientation à partir de chaque déflecteur (172) indiquant ainsi son orientation. Une carte-accès (406) délivre des signaux de commande au module (100) afin d'orienter au moins un déflecteur (172). La carte-accès (406) reçoit aussi les signaux d'orientation produits par ce déflecteur (172) accompagnés des coordonnées qui indiquent une orientation du déflecteur (172). La carte-accès (406) compare les coordonnées reçues avec les signaux d'orientation et ajuste les signaux de commande délivrés au module (100) afin de réduire toute différence entre les coordonnées reçues et les signaux d'orientation. Le commutateur (400) utilise aussi un alignement optique de manière à orienter avec précision des paires de déflecteurs (172) qui couplent un rayon de lumineux (108) entre deux fibres optiques (106).
PCT/US2000/020028 1999-07-21 2000-07-21 Ameliorations apportees a un commutateur a fibres optiques, compact, modulaire et souple WO2001007945A1 (fr)

Priority Applications (4)

Application Number Priority Date Filing Date Title
US10/031,159 US6694072B1 (en) 1999-07-21 2000-07-21 Flexible, modular, compact fiber switch improvements
JP2001512980A JP2003517631A (ja) 1999-07-21 2000-07-21 フレクシブル・モジュラ・コンパクト光ファイバスイッチの改良
EP00947597A EP1210627A1 (fr) 1999-07-21 2000-07-21 Ameliorations apportees a un commutateur a fibres optiques, compact, modulaire et souple
CA002379822A CA2379822A1 (fr) 1999-07-21 2000-07-21 Ameliorations apportees a un commutateur a fibres optiques, compact, modulaire et souple

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US14495399P 1999-07-21 1999-07-21
US60/144,953 1999-07-21

Publications (1)

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WO2001007945A1 true WO2001007945A1 (fr) 2001-02-01

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PCT/US2000/020028 WO2001007945A1 (fr) 1999-07-21 2000-07-21 Ameliorations apportees a un commutateur a fibres optiques, compact, modulaire et souple

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EP (1) EP1210627A1 (fr)
JP (1) JP2003517631A (fr)
CA (1) CA2379822A1 (fr)
WO (1) WO2001007945A1 (fr)

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JP2002258174A (ja) * 2001-03-02 2002-09-11 Seiko Epson Corp 光変調装置及びそれを有する電子機器
WO2002071792A2 (fr) * 2001-03-02 2002-09-12 Teem Photonics Routeurs optiques utilisant des modules d'amplification de positions angulaires
JP2002262318A (ja) * 2001-03-05 2002-09-13 Fujitsu Ltd 光スイッチ
WO2003062894A1 (fr) * 2002-01-18 2003-07-31 Tyco Electronics Raychem Nv Circuits optiques enfermes dans un boitier
EP1444543A1 (fr) * 2001-10-19 2004-08-11 Input/Output, Inc. Commutateur optique numerique et son procede de fabrication
EP1444539A1 (fr) * 2001-10-03 2004-08-11 Continuum Photonics Inc. Appareil de commutation optique et d'orientation de faisceau
EP1476780A1 (fr) * 2002-02-19 2004-11-17 Glimmerglass Networks, Inc. Charniere a torsion longitudinale pliee pour miroir suspendu a la cardan a microsysteme electromecanique
JP2007148429A (ja) * 2001-03-19 2007-06-14 Capella Photonics Inc 再構成可能型光アドドロップ多重化装置
US7233741B2 (en) 2001-10-31 2007-06-19 Fujitsu Limited Optical exchange for wavelength division multiplexed (WDM) network, and optical exchange method for WDM network
EP1890181A1 (fr) * 2001-10-19 2008-02-20 Input/Output, Inc. Appareil de commutation optique numérique et son procédé de fabrication

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JP4876659B2 (ja) * 2006-03-24 2012-02-15 株式会社ニコン 光走査モジュール及びエンコーダ
JP2019015790A (ja) * 2017-07-04 2019-01-31 住友電気工業株式会社 Ｍｅｍｓミラー駆動回路
JP2019191260A (ja) * 2018-04-19 2019-10-31 住友電気工業株式会社 コヒーレント光受信モジュール

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US6002818A (en) * 1997-12-05 1999-12-14 Lucent Technologies Inc Free-space optical signal switch arrangement
US6005993A (en) * 1997-11-14 1999-12-21 Macdonald; Robert I. Deflection optical matrix switch

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US6002818A (en) * 1997-12-05 1999-12-14 Lucent Technologies Inc Free-space optical signal switch arrangement

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2002258174A (ja) * 2001-03-02 2002-09-11 Seiko Epson Corp 光変調装置及びそれを有する電子機器
WO2002071792A2 (fr) * 2001-03-02 2002-09-12 Teem Photonics Routeurs optiques utilisant des modules d'amplification de positions angulaires
WO2002071792A3 (fr) * 2001-03-02 2003-01-03 Teem Photonics Routeurs optiques utilisant des modules d'amplification de positions angulaires
US7031611B2 (en) 2001-03-02 2006-04-18 Teem Photonics Optical routers using angular position amplification modules
JP2002262318A (ja) * 2001-03-05 2002-09-13 Fujitsu Ltd 光スイッチ
JP4657472B2 (ja) * 2001-03-05 2011-03-23 富士通株式会社 光スイッチ
JP2007148429A (ja) * 2001-03-19 2007-06-14 Capella Photonics Inc 再構成可能型光アドドロップ多重化装置
EP1444539A4 (fr) * 2001-10-03 2005-08-17 Continuum Photonics Inc Appareil de commutation optique et d'orientation de faisceau
EP1444539A1 (fr) * 2001-10-03 2004-08-11 Continuum Photonics Inc. Appareil de commutation optique et d'orientation de faisceau
EP1444543A4 (fr) * 2001-10-19 2005-12-14 Input Output Inc Commutateur optique numerique et son procede de fabrication
EP1444543A1 (fr) * 2001-10-19 2004-08-11 Input/Output, Inc. Commutateur optique numerique et son procede de fabrication
US7236279B2 (en) 2001-10-19 2007-06-26 Input/Output, Inc. Digital optical switch apparatus and process for manufacturing same
EP1890181A1 (fr) * 2001-10-19 2008-02-20 Input/Output, Inc. Appareil de commutation optique numérique et son procédé de fabrication
US7233741B2 (en) 2001-10-31 2007-06-19 Fujitsu Limited Optical exchange for wavelength division multiplexed (WDM) network, and optical exchange method for WDM network
WO2003062894A1 (fr) * 2002-01-18 2003-07-31 Tyco Electronics Raychem Nv Circuits optiques enfermes dans un boitier
EP1476780A1 (fr) * 2002-02-19 2004-11-17 Glimmerglass Networks, Inc. Charniere a torsion longitudinale pliee pour miroir suspendu a la cardan a microsysteme electromecanique
EP1476780A4 (fr) * 2002-02-19 2006-06-07 Glimmerglass Networks Inc Charniere a torsion longitudinale pliee pour miroir suspendu a la cardan a microsysteme electromecanique

Also Published As

Publication number Publication date
JP2003517631A (ja) 2003-05-27
CA2379822A1 (fr) 2001-02-01
EP1210627A1 (fr) 2002-06-05

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