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`USUD65675't'4Bt
`
`(I2) United States Patent
`US 6,567,574 BI
`([0) Patent No.:
`Ma et at.
`
`(45) Date of Patent: May 20, 2003
`
`(54) MODULAR THREE-DIMENSIONAL
`OPTICAL SWITCH
`
`(75)
`
`inventors: Jinn Ma, San Diego, (TA (US); Ezekiel
`John Joseph Krugtick, San Diego, (TA
`(US); Daniel J. Reiley, San Diego, CA
`(US); Philippe Jean Mat-chand,
`Poway, (TA (US); Steffen Gtoeckner,
`San Diego, (TA (US)
`
`(73) Assignee: 0mm, Inc., San lJicgo, (A (US)
`
`(‘) Notice:
`
`Subject to any disclaimer, the term ollhis
`patent
`is extended or adjusted under 35
`U.S.C. 15403] by [I days.
`
`(21) App|.No.:i]9168il,648
`(22)
`Filed:
`UCLE, 2000
`
`(51)
`
`Int. Cl.7 .................................................. G023 6126
`
`[52)
`
`ILS. Cl.
`
`(58) Field of Search
`
`3351'16; 385118; 385KB?
`3851’] tJ—EU
`
`(50)
`
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`El’
`EP
`
`References Cited
`US. PA'i‘EN't" DOCUMEN‘I‘S
`231069 Lien ahr
`7.4975 Street
`
`1119?? Wasilko .....
`bt'l‘ifltt
`‘t‘omlinson
`1131980 Leibofi
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`
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`
`
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`
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`
`(List continued on next page.)
`FOREIGN PA'l'lLNT DUCUMENIS
`
`05101529
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`{1902538
`0003-30?
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`331999
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`
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`
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`
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`iloissier, Alain, "Space division optical switching system of
`medium capacities," Proceedings: Fiber Optic Broadband
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`
`I’rt'rttmjv Exmm'ner—Ellen [3. Kim
`(74) Artur-m3; Agent, or Finn—Aricn l-‘errell; Fitch. liven.
`'t'ahin Sr. Planner}r
`
`(5‘!)
`
`ABSTRACT
`
`is
`A modular three—dimensional {3D) optical switch [hat
`scalable and that provides monitor and control ol‘ MEMS
`mirror arrays. A first switch module includes an array of
`input channels. Light beams received from the input chan-
`nels are directed toward a first wavelength selective mirror.
`The light beams are reflected off of the first wavelength
`selective mirror and onto a first array of moveahle micro—
`mirrors. The moveabte micromirrors are adjusted so that the
`light beams reflect
`therefrom and enter a second switch
`module where they impinge upon a second array of move-
`abte micromirrors. The light beams reflect oif of the second
`arrayr of moveable micromirrors and impinge upon a second
`wavelength selective mirror. The light beams reflect oll'ol'
`the second wavelength selective mirror and into an array of
`output channels. The alignment or misalignment of a data
`path through the switch is detected by directing two monitor
`beams through the data path, one in the forward direction
`and one in the reverse direction. The position of each of the
`monitor beams is detected after its reflection from the
`semnd movcable micromirror that it hits. The position data
`is used to determine the angles of the moveable micromir—
`rots in the data path.
`
`(List continued on next page.)
`
`7] Claims, 14 Drawing Sheets
`
`31" i
`
`Detector mar?
`
`grr25
`
`
`
`
`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1023, Page 1
`Exhibit 1023, Page 1
`
`

`

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`4,322,126
`4,365,363
`4,431,258
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`4,566,935
`4,596,992
`4,626,066
`4,630,333
`4,662,746
`4,710,732
`4,796,263
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`5,023,939
`5,037,173
`5 096,279
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`5,177343
`5.199.033
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`5,256,369
`5,233,344
`5,291,324
`5,3 1 1 ,410
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`5,410,371
`5,412,506
`5,420,946
`5,436,936
`5,440,654
`5,444,301
`5,522,796
`5,524,153
`5,621,329
`5,627,669
`5,646,923
`5,647,033
`5.66] .591
`5,743,312
`5,774,604
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`5,303,730
`5,341,917
`5,367,297
`5,873,: 77
`5,903,637
`5,914,301
`5,923,793
`5,933,269
`5,943,454
`5,963,367
`5,969,465
`5,994,159
`5,995,633
`(1,002,818
`6,031,946
`6,031,947
`(1,044,705
`6,037,747
`6,097,353
`6097,3150
`6,101,299
`6,123,935
`6,134,031
`6,154,042
`6,137,103
`6,137,105
`6,137,926
`6,154,533
`6,154,535
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`US 6,567,524 Bl
`Page 2
`
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`
`6,157,026 A
`1272000 Redmel
`6,160,930 A
`1272000 Ferguson
`6,133,314 Bl
`272001
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`6,193,565 131
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`" 1272001 Solgaajd 1:! al.
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`FOREIGN PATENT DOCUMENTS
`
`385716
`3857'1'7
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`EP‘
`EP
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`("702576726
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`1271999
`0962796
`972000
`1033601
`972")”
`1039325
`1272“)”
`“151339
`”2““
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`wo 9304338
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`WO 90724370
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`()IIILR PUBLIC-“10m
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`1993, pp. 048.
`
`"‘ cilcd by examiner
`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1023, Page 2
`Exhibit 1023, Page 2
`
`

`

`US. Patent
`
`May 20, 2003
`
`Sheet 1 0f 14
`
`US 6,567,574 B1
`
`am.“
`
`
`
`«.953373:33
`
`.____________________________.__.____......_-w.-----——-—-———___
`
`9:
`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1023, Page 3
`Exhi
`it 1023, Page 3
`
`
`

`

`US. Patent
`
`May 20, 2003
`
`Sheet 2 0f 14
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`US 6,567,574 B1
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`JDS UNIPHASE CORPORATION
`N40e
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`Exhibit 1023, Page 4
`
`

`

`US. Patent
`
`May 20, 2003
`
`Sheet 3 of 14
`
`US 6,567,574 B1
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`HO
`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1023, Page 5
`Exhibit 1023, Page 5
`
`

`

`US. Patent
`
`May 20, 2003
`
`Sheet 4 of 14
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`US 6,567,574 B1
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`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1023, Page 6
`Exhibit 1023, Page 6
`
`

`

`US. Patent
`
`May 20, 2003
`
`Sheet 5 of 14
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`US 6,567,574 Bl
`
`
`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1023, Page 7
`Exhibit 1023, Page 7
`
`

`

`US. Patent
`
`May 20, 2003
`
`Sheet 6 of 14
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`US 6,567,574 B1
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`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1023, Page 8
`Exhibit 1023, Page 8
`
`

`

`US. Patent
`
`May 20, 2003
`
`Sheet 1' of 14
`
`US 6,567,574 B1
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`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1023, Page 9
`Exhibit 1023, Page 9
`
`

`

`US. Patent
`
`May 20, 2003
`
`Sheet 3 of 14
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`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1023, Page 10
`Exhibit 1023, Page 10
`
`

`

`US. Patent
`
`May 20, 2003
`
`Sheet 9 0f 14
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`US 6,567,574 B1
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`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1023, Page 11
`Exhibit 1023, Page 11
`
`

`

`US. Patent
`
`May 20, 2003
`
`Sheet 10 of 14
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`US 6,567,574 B1
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`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1023, Page 12
`Exhibit 1023, Page 12
`
`

`

`US. Patent
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`May 20, 2003
`
`Sheet 11 of 14
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`US 6,567,574 B1
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`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1023, Page 13
`Exhibit 1023, Page 13
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`US. Patent
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`May 20, 2003
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`JDS UNIPHASE CORPORATION
`Exhibit 1023, Page 14
`Exhibit 1023, Page 14
`
`
`

`

`US. Patent
`
`May 20, 2003
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`Sheet 13 of 14
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`US 6,567,574 B1
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`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1023, Page 15
`Exhibit 1023, Page 15
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`

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`US. Patent
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`May 20, 2003
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`Sheet 14 of 14
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`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1023, Page 16
`Exhibit 1023, Page 16
`
`

`

`US 6,567,574 B1
`
`1
`MODULAR THREE-DIMENSIONAL
`OPTICAL SWITCH
`
`BACKGROUND 0]" THE. INVEN'I‘ION
`]. Field of the invention
`
`invention relates generally to the field of
`The present
`optical switching. More specifically, the present invention
`relates to micro electro mechanical systems (MEMS) tech—
`nology scanning mirrors for optical cross—connects and
`switches.
`2. Discussion of the Related Art
`
`Optical switching plays an important role in telecommu-
`nication networks, optical instrumentation, and optical sig—
`nal processing systems. Optical switches can be used to turn
`the light output of an optical fiber on or off. or. alternatively.
`to redirect
`the light
`to various difierent fibers. all under
`electronic control.
`Optical switches that provide switchable cross connects
`between an array of input fibers and an array ofoutput fibers
`are often referred to as "optical cross-connects". Optical
`cross-connects are a fundamental building block in the
`development of an all-optical communications network.
`Specifically,
`in a fiber-optic communications network that
`uses electronic cross-connects, data travels through many
`fiber-optic segments which are linked together using the
`electronic cross-connects. Information is converted from
`light
`into an electronic signal, routed to the next circuit
`pathway, then converted back into light as it travels to the
`next network destination. In an alloptical communications
`network, on the other hand, the electronic cross-eonnecLs are
`replaced with optical cross-connects, which eliminates the
`need to convert
`the signals between light and electronic
`form. Instead, information travels through the entire network
`in the form of light, which significantly increases the net-
`work‘s ability to handle higher transmission speeds. reduces
`power dissipation,
`increases reliability, and reduces cost
`because the cost of the electrical devices are eliminated.
`There are many different
`types of optical switches. In
`terms of the switching mechanism, optical switches have
`been previously categorized as belonging to one of two
`general classes. The first general class of optical switches
`employs a change of refractive index to perform optical
`switching and can he referred to as "integrated optical
`switches" or "electro—optic switches." The refractive index
`change can be induced by electro-optic,
`thermaloptie,
`acousto-optic, or tree-carrier effects. The second general
`class of optical switches may be referred to as "bulk opto—
`meehanical switches" or simply "optomechanical switches."
`Such switches employ physical motion of one, or more.
`optical elements to perform optical switching. Specifically,
`an input
`fiber,
`typically engaged to a lens,
`is physically
`translatable from a first position to at least a second position.
`In each position, the input fiber optically connects with a
`different output fiber. In this way. a spatial displacement of
`a reflected beam is affected.
`()ptomechanical switches offer many advantages over
`clectro-optic switches. (thomechanical switches have both
`lower insertion loss and tower crosstalk compared to electro-
`optic switches. Further, optomeehanical switches have a
`high isolation between their 0N and OFF states.
`Furthermore, optomeehanical switches are bidirectional. and
`are independent of optical wavelength. polarization. and
`data modulation format. An optomeehanical switch can be
`implemented either in a free—space approach or
`in a
`waveguide {e.g., optical
`fiber} approach. The free-space
`
`Ill
`
`[5
`
`3t]
`
`4n
`
`45
`
`SE]
`
`55
`
`bf]
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`65
`
`2
`approach is more scalable, and offers lower coupling toss
`compared to the waveguide approach.
`A number of different micromachining technologies have
`been developing. Recently, a micromachining technology
`known has micro electro mechanical systems (MEMS)
`technology has been shown to offer many advantages for
`building optomeehanical switches. MEMS technology is
`technology characteristic of sizes from a few millimeters to
`hundreds of micrometers. MEMS technology is similar to
`semiconductor electronics fabrication except that the result—
`ing devices possess mechanical functionality, as well as
`electronic and-”or optical functionality. MEMS technology is
`currently used to fabricate movable microstructures and
`mieroactuators. MEMS can significantly reduce the size.
`weight and cost of optomechanical switches. The switching
`time can also be reduced because of the tower mass of the
`smaller optomechanical switches.
`Many MEMS optomechanical switches and cross-
`connects employ movable micromirrors. MEMS movable
`microminor assemblies may he used for optical scanning.
`That is. MEMS mirror assemblies may be used to rapidly
`traverse a range of positions in a coordinate axis. Thus,
`MEMS mirror assemblies may be used as a basic building
`block for optical scanners. Optical scanners are ideal for use
`in optical cross—tx‘tnnects. Optical scanners function by
`changing the angle of the optical beam with respect to the
`information medium. Various different types of scanners are
`capable of operating in one dimension (ID). two dimensions
`(EU), or even three dimensions (30).
`A 21) optical cross-connect (or switch) can be constructed
`by using MEMS nlicromirrors that move in only It). For
`example. by using vertical micromirrors. where the mirror
`surface is perpendicular to the substrate, a simple cross-
`connect (or matrix switch} with a regular planar array of
`switching cells can be realized. The input and output fibers
`are arranged in the same plane as the matrix substrate. When
`a switching or cross—connect operation is performed.
`the
`optical beam is redirected by one or more of the vertical
`micromirrors, but
`the optical beam does not
`leave the
`common plane of the input and output
`fibers. Thus,
`the
`vertical micromirrors move in 10 and are used to perform
`optical cross—connections in 2D.
`Adisadvantage onD optical cross-connects(or switches)
`is that they are limited in the number of input and output
`fibers that they can support since those fibers are arranged in
`the same plane as the matrix substrate. In today‘s rapidly
`expanding communications systems there is
`a strong
`demand for higher capacity optical switches. Thus, there is
`a need for optical cross-connects and switches that can
`support a greater number of input and output fibers and that
`have the ability to cross-connect any of the input fibers with
`any of the output fibers.
`SUMMARY 01“ THE lNVENllON
`
`The present invention advantageously addresses the needs
`above as well as other needs by providing a method of
`detecting alignment of an optical path through an optical
`switch. The method includes the steps of: directing a first
`monitor beam in a forward direction along at least a portion
`of the optical path, the at least a portion of the optical path
`including reflection 011' of a first moveable optical redirect—
`ing device and a second moveable optical redirecting device:
`detecting a position of the first monitor beam that is reflected
`ofi' of the second moveable optical redirecting device; direct-
`ing a second monitor beam in a reverse direction along the
`at least a portion of the optical path; and detecting a position
`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1023, Page 17
`Exhibit 1023, Page 17
`
`

`

`US 6,567,574 B1
`
`llil
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`of the second monitor beam that is reflected oil“ of the first
`moveable optical redirecting device.
`The present invention also provides a method of switch—
`ing an optical input channel to an optical output channel. The
`method includes the steps of: directing a light beam that
`originates from the optical
`input channel
`toward a
`first
`moveable optical redirecting device; reflecting the light
`beam off of the first movcablc optical redirecting device and
`onto a second moveable optical redirecting device; reflecting
`the light beam ofl'of the second rnoveable optical redirecting
`device; directing the light beam reflected ofi‘ ot' the second
`moveable optical redirecting device into the optical output
`channel; and directing a first monitor beam along at least a
`portion of a same path traveled by the light beam.
`The present invention also provides a method of switch-
`ing an optical input channel to an optical output channel that
`includes the steps of: directing a light beam received from
`the optical input channel toward a first wavelength selective
`optical redirecting device: reflecting the light beam off of the
`first wavelength select ive optical redirecting device and onto
`a first moveahle optical redirecting dcvice; adjusting the first
`movcable optical redirecting device so that the light beam
`reflects therefrom and impinges upon a second moveable
`optical redirecting device; adjusting the second moveable
`optical redirecting device so that
`the light beam reflects .
`therefrom and impinges upon a second wavelength selective
`optical redirecting device; and reflecting the light beam (ad
`of the second wavelength selective optical redirecting device
`and into the optical output channel.
`The present invention also provides an apparatus for use
`in optical switching. The apparatus includes a first switch
`module and a second switch module. The first switch
`module includes an optical input channel, a first moveahle
`optical redirecting device, and a first wavelength selective
`optical redirecting device positioned to reflect a light beam
`received from the optical input channel onto the first movcm
`able optical redirecting device. The second switch module
`includes an optical output channel.
`a second moveahle
`optical redirecting device. and a second wavelength selec-
`tive optical redirecting device positioned to reflect the light
`beam received from the second moveable optical redirecting
`device into the optical output channel. The first switch
`module and the second switch module are positioned so that
`the light beam can be rellccted from the first moveable
`optical redirecting device and impinge upon the second
`moveable optical redirecting device.
`The present invention also provides an apparatus for use
`in optical switching that includes a first switch module. The
`first switch module includes an optical input channel, a first
`moveahle optical redirecting device, and a first wavelength
`selective opticaI redirecting device positioned to reflect a
`light beam received from the optical input channel onto the
`lirst moveable optical redirecting device. A detector is
`configured to detect a position of a first monitor beam that
`is reflected off of the first movcahle optical redirecting
`device and that at least a portion of which is transmitted
`through the first wavelength selective optical redirecting
`device.
`A better understanding of the features and advantages of
`the present invention will be obtained by reference to the
`following detailed description of the invention and accom-
`panying drawings which set forth an illustrative embodiment
`in which the principles of the invention are utilimd.
`BRIEF DESCRIPTION OF THE DRAWINGS
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`The above and other aspects, features and advantages of
`the present invention will be more apparent from the fol-
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`4
`lowing more particular description thereof presented in
`conjunction with the following drawings herein;
`FIG. 1 is a perspective view illustrating a modular optical
`switch made in accordance with the present invention;
`FIG. 2 is a schematic, side view illustrating the modular
`optical switch shown in FIG. I;
`FIGS. 3A and 3B are schematic, side views illustrating
`optical switches that use multiple modules of the type shown
`in [’16.
`l in accordance with the present invention;
`FIG. 4 is a top view illustrating one of the scanner chips
`shown in FIG. 1;
`FIG. 5 is
`a perspective view illustrating one of the
`micromirror assemblies shown in FIG. 4;
`FIGS. 6A and 63 are perspective vieWs illustrating the
`operation of the micromirror assembly shown in FIG. 5;
`FIG. 7 is a top view illustrating one of the monitoring
`(detector) chips shown in FIG. 1;
`FIG. 8 is a schematic, side view further illustrating the
`operation of the moduiar optical switch shown in FIG. 1;
`FIGS. 9 and 10 are schematic, side views illustrating an
`alternative modular optical switch made in accordance with
`the present invention;
`FIG. 11 is a schematic, side view illustrating another
`alternative modular optical switch made in accordance with
`the present invention;
`FIG. 12 is a schematic, side view illustrating another
`alternative modular optical switch made in accordance with
`the present invention; and
`FIG. 13 is a schematic, side view illustrating another
`alternative modular optical switch made in accordance with
`the present invention.
`DETAILED DESCRIPTION {)F A PREi-‘ERREIJ
`EMBODIMENT
`
`The following description is not to be taken in a limiting
`sense, but is made for the purpose of describing one or more
`embodiments of the invention. The scope of the invention
`should be determined with reference to the claims.
`Referring to FIGS.
`1 and 2., there is illustrated an optical
`switch 100 made in accordance with an embodiment of the
`present
`invention. The optical switch 100 is a three-
`dirnensional (3D) optical switch that is capable of providing
`switchable cross connects between an array of input tibers
`and an array of output fibers. In other words, each of a
`plurality of single-wavelength optical input channels from
`the input fibers can be directed to a desired optical through
`channel of the output fibers.
`Because the optical switch 100 (or optical cross-connect
`100) is a 3D switch, there are multiple rows of input and
`output fibers that occupy multiple planes. In other words, the
`input and output fibers are not all arranged in the same plane
`as a common substrate. This allows an optical beam from an
`input fiber in one plane to be cross-connected or switched to
`an output fiber in a different plane. Thus, the ED optical
`switch 100 provides an army of free—space optical connec—
`tions between input and output fibers located in dil‘fercnt
`planes. The use of input and output fibers in diderent planes
`allows for a potentially greater number of input and output
`fibers than a 2D optical switch, which results in greater
`capacity.
`As will be discussed below. the optical switch 100 pref-
`erably uses 2!) MEMS optical scanners. it has been found
`herein that EU scanners are ideal for implementing SD
`optical crass-connects, i.e., optical cross-eonnechs where the
`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1023, Page 18
`Exhibit 1023, Page 18
`
`

`

`US 6,567,574 131
`
`5
`input and output fibers are not arranged in the same plane as
`a common substrate. Furthermore, the input and output of
`the optical switch 100 are preferably symmetric, which
`makes the switch 101]I convenient for bidirectional operation.
`In accordance with the present
`invention,
`the optical
`switch 100 uses a modular scheme. Specifically. the optical
`switch 100 includes a first module 102 and a second module
`Ill-4. Either one of the modules 102 or 104 may he referred
`to as a 3!) optical switch module that, preferably, uses
`MEMS mirror scanners. 1n the illustrated embodiment the
`first and second modules 102, 104 are substantially identical,
`but it should be understood that there may be minor varia-
`tions between the first and seconrl modules 102, [04 in some
`embodiments of the invention.
`In the illustrated embodiment, the lirst module 102 con—
`nects to an array of input fibers 110 and includes wavelength
`division multiplexers {WDM} 111. an input collimator array
`112, a first mirror 114, a first scanner chip 116, and a first
`monitoring chip 118. Similarly, the second module 104 is
`connected to an array of output
`fibers 120 and includes
`wavelength division multiplexers 121, an output collimator
`array 122, a second mirror 124, a second scanner chip 126,
`and a second monitoring chip 128. As an optional feature, an
`array of monitoring beams 1.30 may be tapped into the army
`of input fibers 110 by tap couplers. and an array of moni-
`toring beams [31 (discussed below) may he tapped into the
`array of output fibers 120 by tap couplers.
`it should be
`understood that
`the monitoring beams (also referred to
`herein as the “monitoring wavelength") may either be
`tapped into the input and output fibers 110. 120 as shown. or
`alternatively, beam splitters may he employed in the mod—
`ules 102, 104 to receive the monitoring beams indepen-
`dently of the input and output fibers 110, 120. The use of
`such beam splitters will be discussed below.
`The first mirror 114 is preferably positioned to receive
`light beams from the array of input fibers 110 via the input
`collimator array 112 (i.e., the input channels) and to reflect
`the light beams in a direction substantially normal to the
`array ol'input channels. By way of example. the first mirror
`[14 may be positioned at a 45° angle with respect to the
`input channels and have iLs reflective surface facing the
`input channels. Similarly, the second mirror 124 is prefer-
`ably positioned to reflect light beams into the array ofoutput
`fibers 120 via the output collimator array 122 (i.e., the output
`channels). In the illustrated embodiment the second mirror
`124 receives the light beams from a direction substantially
`normal to the array of output channels. By way of example,
`the second mirror 124 may be positioned at a 45° angle with
`respect to the output channels and have its reflective surface
`facing the output channels. While 45° is an exemplary
`orientation for the first and second mirrors 1.14, 124,
`it
`should be well understood that a 45° orientation is not
`required and that the first and second mirrors 1l4, 124, as
`well as the first and second scanner chips 116, 126, may be
`oriented at many other angles in accordance with the present
`invention.
`The first and second mirrors 114, 124 preferably comprise
`wavelength selective mirrors or dichroic mirrors. A wave—
`length selective mirror can be used to reflect signal wave-
`lengths and transmit all or a portion of a monitoring wave-
`length.
`ln other words, a wavelength selective minor is
`partially transmissive for all or a portion of a certain
`wavelength of tight. The certain wavelength of light can
`conveniently be used as a monitoring wavelength. It should
`be well understood that the percentage of transmissiveness
`and rellectivcness of the mirrors 114, 124 may vary greatly
`in accordance with the present
`invention. Preferably,
`the
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`wavelength selective mirrors 114, 124 comprise layered
`dielectric mirrors that are partially transparent for the moni-
`toring wavelength, but use of layered dielectric mirrors are
`not required. Because one function of a mirror is to redirect
`optical beams, the wavelength selective mirrors 114, 124
`may also be refcrrcd to as wavelength selective optical
`redirecting devices.
`The first scanner chip 116 provides the function of a
`director.
`i.e..
`it selects the output channel. The second
`scanner chip 126 provides the function of a redirector, i.e.,
`it ensures coupling into the output fibers 120. Thus,
`the
`director and re-director are preferably scanner based. The
`distance between the first scanncr chip 116 (director) and the
`second scanner chip 126 (redirector) and the loss budget
`determine the required scan angles. The scan angles will be
`discussed in more detail below.
`Although the illustrated optical switch 100 comprises a
`4x4 structure having sixteen inpuLs and sixteen outputs,
`it
`should be well understood that the specific number of inputs
`and outputs can vary greatly in accordance with the present
`invention. For example, 8x8, 64x64. and larger structures
`can all be made in accordance with the teachings of the
`present invention.
`One advantage of the optical switch 100‘s modular
`scheme is that stand-alone optical switches can be made that
`are highly scalable. In other words, multiple modules can be
`used to accommodate large numbers of inputs and outputs.
`For example, FIGS. 3A and 3!} illustrate exemplary versions
`or optical switches that are constructed using multiple
`numbers of the first and second modules 102, 104. Either
`more or fewer of the input modules 102. and either more or
`fewer of the output modules 104. may be used to accom-
`modate the desired number of inputs and outputs, respec~
`tively. It should he understood that the total number of inputs
`does not have to be equal to the total number of outputs.
`Another advantage of the modularity of the optical
`switches of the present
`invention is that
`the individual
`modules are hot swapable.
`In other words. any of the
`modules can be removed and changed while the switch is
`ru nning. This feature makes configuring and maintaining the
`switch particularly easy.
`ReferTing to FIG. 4, there is illustrated the upper surface
`of an exemplary version of the first scanner chip 116. Art
`identical or substa ntially similar chip is preferably employed
`as the second scanner chip 126. 'lhe first scanner chip 116
`includes an array 140 of movcable micromirrors formed on
`a substrate 142. Because one function of a mirror is to
`redirect optical beams, the movable micromirrors may also
`he referred to as movable optical redirecting devices. Each
`of the movable micromirrors is part of an optomechanical
`switching cell. The mirror array 140 is preferably fabricated
`in accordance with Micro Electro Mechanical Systems
`(MEMS) technology. Furthermore, the mirror array 140 is
`preferably configured to operate as a two-dimensional (20)
`optical scanner. 2]) optical scanners with large rotation
`angles. narrow beam divergence, and high resonant fre-
`quency can be implemented with MEMS technology.
`MEMS technology is attractive for
`reducing the size,
`weight, and complexity of the optical scanners.
`The mirror array 140 includes several MEMS mirror
`assemblies