(12) United States Patent
`Bouevitch et al.
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 6,498,872 B2
`Dec. 24, 2002
`
`US006498872B2
`
`(54)
`
`(75)
`
`OPTICAL CONFIGURATION FOR A
`DYNAMIC GAIN EQUALIZER AND A
`CONFIGURABLE ADD/DROP
`MULTIPLEXER
`
`Inventors: Oleg Bouevitch, Gloucester (CA);
`Thomas Ducellier, Ottawa (CA); W.
`John Tomlinson, Princeton, NJ (US);
`Paul Colbourne, Nepean (CA);
`Jacques Bismuth, Ottawa (CA)
`
`4/1998
`5,740,288 A
`4/1998
`5,745,271 A
`12/1998
`~,847,831 A
`2/1999
`5.867,264 A
`3/1999
`5.881,199 A
`&q 999
`5.936,752 A
`8/1999
`5.943,158 A
`9/1999
`5.960,133 A
`1/2000
`6.018,603 A
`6/2000
`6.081,331 A
`10/2000
`6.134,359 A
`6,415,080 B1 * 7/2002
`
`Pan ............................. 385/11
`Ford et al ................... 359/130
`Tomlinson, III et al ..... 356/364
`Hinnrichs ................... 356/310
`Li .............................. 385/140
`Bishop et al ............... 359/124
`Ford et al ................... 359/295
`Tomlinson ................... 385/18
`Lundgren et al .............. 385/33
`Teichmann ................. 356/328
`Ke~,’orth et al ............. 385/33
`Sappey et al ............... 359/127
`
`(73)
`
`Assignee: JDS Uniphase Inc., Ottawa (CA)
`
`* cited by examiner
`
`Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 17 days.
`
`Primary Examiner~ttemang Sanghavi
`Assistant Examiner~gmar Rojas
`(74) Attornc3,, Agent, or Firm~acasse & Associates, LLC
`
`(21) Appl. No.: 09/729,270
`
`(22) Filed:
`
`Dec. 5, 2000
`
`(65)
`
`Prior Publication Data
`
`US 2002/0009257 A1 Jan. 24, 2002
`
`Related U.S. Application Data
`(60) Provisional application No. 60/183,155, filed on Feb. 17,
`2000.
`
`Int. CI.7 ............................. G02B 6/28; II04J 14/(12
`(51)
`(52) U.S. C1 ............................ 385/24; 385/37; 359/130;
`359/246; 359/247; 359/301; 359/302; 359/128
`(58) Field of Search ................................. 349/193, 196;
`359/115, 122, 128, 124, 130, 131, 245-247,
`301-302; 385/16, 18, 24, 31, 37, 39, 47
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`4,367,040 A
`4,707,056 A
`4,839,884 A
`5,233,405 A
`5,311,606 A
`5,414,540 A
`5,477,350 A
`5,526,155 A
`
`1/1983 Goto ........................... 356/44
`11/1987 Bittner .................... 350/96.12
`6/1989 Sehloss ......................... 370/3
`8/1993 Wildnaucr ct al ........... 356/333
`5/1994 Asakura et al ......... 359/337.21
`5/1995 Patel et al .................. 349/196
`12/1995 Riza et al ..................... 359,/39
`6/1996 Knox et al .................. 359/130
`
`(57)
`
`ABSTRACT
`
`An optical device for rerouting and modifying an optical
`signal that is capable of operating as a dynamic gain
`equalizer (DGE) and/or a configurable optical add/drop
`multiplexer (COADM) is disclosed. The optical design
`includes a front-end unit for providing a collimated beam of
`light, an clcmcnt having optical powcr for providing
`collimating/focusing effects, a diffraction element for pro-
`viding spatial dispcrsion, and modifying mcans which in a
`preferred embodiment includes one of a MEMS array and a
`liquid crystal array for reflecting and modifying at least a
`portion of a beam of light. The modifying means functions
`as an attenuator when the optical device operates as a DGE
`and as a switching array when the optical device operates as
`a COADM. Advantageously, this invention provides a 44
`system w-herein a preferred embodiment the element having
`optical power is a concave reflector for providing a single
`means for receiving light from the front-end unit, reflecting
`the received light to the dispersive element, receiving light
`t]:om the dispersive element, and providing dispersed light to
`the modifying means. Conveniently and advantageously,
`this same concave reflector is utilized on a return path,
`obviating the requirement of matching elements. In one
`embodiment a single focussing/collimating lens is provided
`substantially at a focal plane of the element having optical
`power.
`
`41 Claims, 12 Drawing Sheets
`
`620 ~
`
`610
`
`Petitioner Ciena Corp. et al.
`Exhibit 1003-1
`
`

`

`U.S. Patent
`
`Dec. 24, 2002
`
`Sheet 1 of 12
`
`US 6,498,872 B2
`
`l~Oa
`
`120
`
`1!0b
`
`150
`
`OA
`
`I02a
`
`102b
`
`FIG. 1
`
`Petitioner Ciena Corp. et al.
`Exhibit 1003-2
`
`

`

`U.S. Patent
`
`Dec. 24, 2002
`
`Sheet 2 of 12
`
`US 6,498,872 B2
`
`Fi_q ure 2a.
`
`Figure 2b.
`
`Petitioner Ciena Corp. et al.
`Exhibit 1003-3
`
`

`

`U.S. Patent
`
`Dec. 24, 2002
`
`Sheet 3 of 12
`
`US 6,498,872 B2
`
`130
`
`o
`
`.__~144
`
`,/ ~ 146
`
`102a
`
`102b
`
`FIG. 3a
`
`~o -~
`
`130 "/-""
`
`L140
`
`144
`
`.~//J"-~..~ 146
`
`L140
`
`102a
`
`102b
`
`FIG. 3b
`
`lO2a
`
`102b
`
`FIG. 3c
`
`102a
`
`I02b
`
`FIG. 3d
`
`Petitioner Ciena Corp. et al.
`Exhibit 1(303-4
`
`

`

`U.S. Patent
`
`Dec. 24, 2002
`
`Sheet 4 of 12
`
`US 6,498,872 B2
`
`152
`
`142
`
`153
`
`o
`
`153
`
`102a
`
`102b
`
`102a
`
`102b
`
`102a
`
`102b
`
`FIG. 4a
`
`150
`
`152
`
`/142
`
`FIG. 4b
`
`150
`
`’5 _~ 155
`
`FIG. 5
`
`~"N150
`
`Petitioner Ciena Corp. et al.
`Exhibit 1003-5
`
`

`

`U.S. Patent
`
`Dec. 24, 2002
`
`Sheet 5 of 12
`
`US 6,498,872 B2
`
`620 ~
`
`610
`
`FIG. 6a
`
`620
`
`~/.-~ 610
`
`657
`
`660
`
`- 650 670
`
`FIG. 6b
`
`

`

`U.S. Patent
`U.S. Patent
`
`Dec. 24, 2002
`Dec. 24, 2002
`
`Sheet 6 of 12
`Sheet 6 of 12
`
`US 6,498,872 B2
`US 6,498,872 B2
`
`
`
`605
`
`650
`
`610
`
`FIG. 7
`
`Petitioner Ciena Corp. et al.
`Petitioner Ciena Corp. et al.
`Exhibit 1003-7
`Exhibit 1003-7
`
`

`

`U.S. Patent
`
`Dec. 24, 2002
`
`Sheet 7 of 12
`
`US 6,498,872 B2
`
`/
`
`805 1/~8~2
`
`m OA
`
`840
`
`825
`
`FIG. 8
`
`910
`
`992
`
`990
`
`987
`
`,996
`
`998
`
`¯ OA2
`
`994
`
`985
`993
`
`999
`
`OA
`
`?40
`
`930
`
`925
`
`FIG. 9
`
`Petitioner Ciena Corp. et al.
`Exhibit 1003-8
`
`

`

`U.S. Patent
`
`Dec. 24, 2002
`
`Sheet 8 of 12
`
`US 6,498,872 B2
`
`£12
`
`998
`
`990X~ 913\
`
`OA 2
`
`FIG. 9a
`
`912
`
`998
`
`OA 2
`
`999
`
`916
`
`FIG. 9b
`
`990-,~ 916
`
`914
`
`912
`
`996
`
`998,999
`
`1
`9
`
`8
`
`FIG. 9c
`
`Petitioner Ciena Corp. et al.
`Exhibit 1003-9
`
`

`

`U.S. Patent
`
`Dec. 24, 2002
`
`Sheet 9 of 12
`
`US 6,498,872 B2
`
`916 994 993
`
`FIG. 9d
`
`998
`
`999
`
`999
`
`OA 2
`
`FIG. 9e
`
`913 912 /996
`
`///~998
`
`J~2d : D
`---~
`
`~"998
`
`FIG. 9f
`
`Petitioner Ciena Corp. et al.
`Exhibit 1003-10
`
`

`

`U.S. Patent
`US. Patent
`
`Dec. 24, 2002
`Dec. 24, 2002
`
`Sheet 10 0f 12
`Sheet 10 of 12
`
`US 6,498,872 B2
`US 6,498,872 B2
`
`
`
`a \
`.-
`
`§
`
`9258
`
`940
`
`930
`
`FIG.10
`
`7
`
`__l
`
`*1?“
`.\\\\\\\\V
`
`
` 925b
`
`Petitioner Ciena Corp. et al.
`F?fifiona%]ena(kmpefiaL
`Exhibit 1003-11
`Exhibit 1003-11
`
`m 0(
`
`\l
`0)
`
`

`

`U.S. Patent
`US. Patent
`
`Dec. 24, 2002
`Dec. 24, 2002
`
`Sheet 11 0f 12
`Sheet 11 of 12
`
`US 6,498,872 B2
`US 6,498,872 B2
`
`OUT DROP
`
`80b
`/
`
`OUT EXPRESS
`
`(\1
`<12
`0
`
`0')
`
`i
`
`I
`
`IN
`
`908512a96
`
`
`
`
`
`i } -:_-_.. l\25
`
`FIG.11
`
`/
`/
`/
`/
`/
`/
`
`I
`
`I
`I
`
`I
`! /
`I/
`1/
`
`I
`I
`I
`I
`
`Petitioner Ciena Corp. et al.
`Petitioner Ciena Corp. et al.
`Exhibit 1003-12
`Exhibit 1003-12
`
`

`

`U.S. Patent
`US. Patent
`
`Dec. 24, 2002
`Dec. 24, 2002
`
`Sheet 12 0f 12
`Sheet 12 of 12
`
`US 6,498,872 B2
`US 6,498,872 B2
`
`0A2
`
`Aw—
`
`98
`
`99
`
`«4.2!;7—1-
`_x
`
`51'
`
`I
`I
`
`;J____
`
`’(,50
`
`i _,
`
`I i
`
`FIG.12
`
`Petitioner Ciena Corp. et al.
`Petitioner Ciena Corp. et al.
`Exhibit 1003-13
`Exhibit 1003-13
`
`20
`
`_ v
`
`96
`
`90123
`
`N0
`
`)
`
`10/
`N
`
`F
`
`

`

`US 6,498,872 B2
`
`1
`OPTICAL CONFIGURATION FOR A
`DYNAMIC GAIN EQUALIZER AND A
`CONFIGURABLE ADD/DROP
`MULTIPLEXER
`
`This application claims the benefit of Ser. No. 60,/183,
`155, filed Feb. 17, 2(1(1(I.
`
`FIEI,D OF THE INVENTION
`
`The present invention relates to an optical device for
`rerouting and modifying an optical signal, or more
`specifically, to an optical configuration including a diffrac-
`tion grating that can be used for a dynamic gain equalizer
`and/or a configurable add!drop multiplexer.
`
`BACKGROUND OF THE INVENTION
`
`In optical wavelength division multiplexed (WDM) com-
`munication systems, an optical ~vavcguidc simultancously
`carries many different communication channels in light of
`different wavelengths. In WDM systems it is desirable to
`cnsurc that all channcls have ncarly cquivalcnt power. To
`help achieve this, gain equalizers are disposed at various
`points throughout the system to control the relative power
`lcvcls in rcspcctivc channcls. Dense WDM systcms rcquirc
`special add/drop multiplexers (ADM) to add and drop
`particular channels (i.e., wavelengths). For example, at
`predetermined nodes in the system, optical signals of pre-
`determined wavelength are dropped from the optical
`waveguide and others are added.
`Typically, gain equalizing and add/drop multiplexer
`devices involve some form of multiplexing and demulti-
`plcxing to modify cach individual channcl of thc tclccom-
`munication signal. In particular, it is common to provide a
`first diffraction grating for demultiplexing the optical signal
`and a second spatially separated diffraction grating for
`multiplexing the optical signal after it has been modified. An
`example of the latter is disclosed in U.S. Pat. No. 5,414,540,
`incorporated herein by reference. However, in such
`instances it is necessary to provide and accurately align two
`matching diffraction gratings and at least two matching
`lenses. This is a significant limitation of prior art devices.
`To overcome this limitation, other prior art devices have
`opted to providc a singlc diffraction grating that is uscd to
`demultiplex an optical signal in a first pass through the
`optics and multiplex the optical signal in a second pass
`through thc optics. For cxamplc, U.S. Pat. Nos. 5,233,405,
`5,526,155, 5,745,271, 5,936,752 and 5,960,133, which are
`incorporated herein by reference, disclose such devices.
`However, none of these prior art devices disclose an
`optical arrangement suitable for both dynamic gain equalizer
`(DGE) and configurablc optical add/drop multiplcxcr
`(COADM) applications. In particular, none of these prior art
`devices recognize the advantages of providing a simple,
`symmctrical optical arrangcmcnt suitablc for usc with vari-
`ous switching/attenuating means.
`Moreover, none of the prior art devices disclose a
`multiplexing/demultiplexing optical arrangement that is
`compact and compatible with a ph~rality of parallel input/
`output optical waveguides.
`For example, U.S. Pat. No. 5,414,540 to Patel et al.
`discloses a liquid crystal optical switch for switching an
`input optical signal to selected output channels. The switch
`includes a diffraction grating, a liquid crystal modulator, and
`a polarization dispersive element. In one embodiment, Patel
`et al. suggest extending the lx2 switch to a 2x2 drop-add
`
`2
`circuit and using a reflector. However, the disclosed device
`is limited in that the add/drop beams of light are angularly
`displaced relative to the input!output beams of light. This
`angular displacement is disadvantageous with respect to
`5 coupling the add/drop and/or input/output beams of light
`into parallel optical waveguides, in addition to the additional
`angular alignment required for the input beam of light.
`With respect to compactness, prior art devices have been
`limited to an excessively long and linear configurations,
`10 xvherein the input beam of light passes through each optical
`component sequentially before being reflected in a substan-
`tially backwards direction. U.S. Pat. No. 6,081,331 discloses
`an optical device that uses a concave mirror for multiple
`rcflcctions as an altcrnativc to using two lcnscs or a doublc
`15 pass through one lens. However, the device disclosed therein
`only accommodates a single pass through the diffraction
`grating and does not realize the advantages of the instant
`invention.
`It is an object of this invention to provide an optical
`20 system including a diffraction grating that is relatively
`
`compact.
`It is a further object of the instant invention to provide an
`optical configuration for rerouting and modifying an optical
`signal that can be used as a dynamic gain equalizer and/or
`configurable add/drop multiplexer.
`
`2s
`
`SUMMARY OF THE INVENTION
`
`35
`
`The instant invention provides a 4-f optical system com-
`3o prising a dispersive element for spatially separating an input
`optical signal into different spectral channels and a modi-
`fying array for selectively modifying each of the different
`spectral channels. At least one element having optical power,
`such as a lens or a spherical mirror, provides optical com-
`munication between the dispersive element and the modi-
`fying array.
`Conveniently and advantageously, the dispersive element
`and the modifying array are disposed substantially at a focal
`plane of the at least one element having optical power.
`4o Moreover, the dispersive element and element having opti-
`cal power are used in a first and a second pass through the
`optics, thus obviating the requirement of providing matching
`elements.
`In accordance with the instant invention there is provided
`45 an optical device comprising: a first port for launching a
`beam of light; first redirecting means disposed substantially
`one focal length away from the first port for receiving the
`beam of light, the first redirecting means having optical
`power; a dispersive element disposed substantially one focal
`so length away from the first redirecting means for dispersing
`the beam of light into a plurality of sub-beams of light;
`second redirecting means disposed substantially one focal
`length away from the dispersive element for receiving the
`dispersed beam of light, the second redirecting means hav-
`s5 ing optical power; and, modifying mearts optically disposed
`substantially one focal length away from the second redi-
`recting means for selectively modifying each sub-beam of
`light and for rcflccting cach of thc modificd sub-bcams back
`to the second redirecting means, wherein each sub-beam of
`~0 light is incident on and reflected fi-mn the modifying means
`along substantially parallel optical paths.
`In accordance with the instant invention there is provided
`an optical device for rerouting and modifying an optical
`signal comprising: a first port for launching a beam of light;
`(,5 a concave reflector having a focal plane for receiving a beam
`of light launched from the first port; a dispersive element
`disposed substantially at the focal plane for spatially dis-
`
`Petitioner Ciena Corp. et al.
`Exhibit 1003-14
`
`

`

`US 6,498,872 B2
`
`3
`persing a beam of light reflected by the concave reflector and
`for redirecting a spatially dispersed beam of light back to the
`concave reflector; and modifying means disposed substan-
`tially at the focal plane for modifying the spatially dispersed
`beam of light reflected by the concave reflector and for
`reflecting the modified spatially dispersed beam of light
`back to one of the first port and a second port via the concave
`reflector and the dispersive element.
`In accordance with the instant invention there is further
`provided a method of rerouting and modifying an optical
`signal comprising the steps of: lannching a beam of light
`towards an element having optical power off an optical axis
`thereof; redirecting the beam of light incident on the element
`having optical power to a dispersive element disposed
`substantially one focal length away from the element having
`optical power; spatially dispersing the redirected beam of
`light into a plurality of different sub-beams of light corre-
`sponding to a plurality of different spectral channels with a
`dispersive element disposed substantially one focal length
`a~vay from the element having optical power; redirecting the
`pluraliU of different sub-beams of light to a modifying
`means optically disposed substantially two focal lengths
`a~vay from the dispersive element; selectively modifying the
`plurality of different sub-beams of light and reflecting them
`in a substantially bac!,avards direction; and redirecting the
`sclcctivcly modificd plurality of diffcrcnt sub-bcams to thc
`dispersive element and combining them to form a single
`output beam of light, wherein the plurality of different
`sub-bcams of light and thc sclcctivcly modificd plurality of
`different sub-beams follow substantially parallel optical
`paths to and from the modifying means, respectively.
`In accordance with the instant invention there is provided
`an optical device for rerouting and modifying an optical
`signal comprising: a lcns including a first cnd having a singlc
`port coincident with an optical axis thereof and a second end
`having two ports disposed off the optical axis; an element
`having optical powcr disposcd about onc focal lcngth away
`from the lens for receiving a beam of light launched from the
`single port; a dispersive element disposed about one focal
`lcngth away from thc clcmcnt having optical po~vcr for
`spatially dispersing a beam of light received therefrom; and
`modifying means optically disposed about two focal lengths
`away from thc dispcrsivc clement for modifying and rcflcct-
`ing a beam of light spatially dispersed by the dispersive
`element, wherein said one focal length is a focal length of
`the element having optical power.
`In accordance with the instant invention there is provided
`a mcthod of modifying and rcrouting a bcam of light
`comprising the steps of: launching the beam of light through
`a first port disposed about a first end of a lens off the optical
`axis of the lens, the beam of light launched in a direction
`parallel to the optical axis; allowing the beam of light to pass
`through the lens to a single port disposed about an opposite
`side of the lens coincident with the optical axis, and allowing
`the beam of light to exit the single port at a first predeter-
`mined angle to the optical axis; modifying the beam of light
`and reflecting the modified beam of light back to the single
`port at a second predetermined angle to the optical axis; and,
`allowing the modified beam of light to pass through the lens
`to a second port disposed about the first end of the lens, the
`second port disposed off the optical axis and spatially
`separated t]:om the first port.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`Exemplary embodiments of the invention will now be
`described in cot~iunction with the drawings in which:
`
`4
`FIG. I is a schematic diagram illustrating an embodiment
`of an optical configuration that can be used as a dynamic
`gain eqnalizer and/or add-drop mnltiplexer (DGE!COADM)
`in accordance with the invention;
`FIG. 2a is a detailed side view of a front-end module for
`use with the DGE/COADM shown in FIG. 1 having means
`for compensating for polarization mode dispersion (PMD);
`FIG. 2b is a detailed side view of an alternative front-end
`module having means for reducing or substantially elimi-
`~0 nating PMD;
`
`5
`
`FIG. 3a is a top view of one embodiment of modifying
`means comprising a liquid crystal array for use with the
`DGE!COADM shown in FIG. 1, wherein a liquid crystal
`element is switched to an ON state;
`FIG. 3b is a top view of the modifying means shown in
`FIG. 3a, wherein the liquid crystal element is switched to an
`OFF state;
`FIG. 3c is a top view of another embodiment of the
`2o modifying means for use widi the DGE!COADM shown in
`FIG. 1, whcrcin thc liquid crystal clcmcnt is s~vitchcd to an
`ON state;
`FIG. 3d is a top vie~v of the modifying means shown in
`FIG. 3c, wherein the liquid crystal element is switched to an
`25 OFF state;
`
`FIG. 4a is a top view of another embodiment of the
`modifying means for use with the DGE!COADM shown in
`FIG. 1 having a birefringent crystal positioned before the
`liquid crystal array, wherein the liquid crystal element is
`3o switched to an OFF state;
`
`FIG. 4b is a top view of the modifying means shown in
`FIG. 4a, whcrcin the liquid crystal clcmcnt is switched to an
`ON state;
`
`35 FIG. 5 is a top vicw of yct anothcr cmbodimcnt of thc
`modifying means for use with the DGE shown in FIG. 1
`utilizing a MEMS device;
`FIGS. 6a and 6b are schematic diagrams of an embodi-
`ment of the invention that is preferred over the one shown
`4o in FIG. 1, wherein the focal plane of a single concave
`reflector is used to locate the input/output ports, diffraction
`grating, and modifying means;
`FIG. 7 is a schematic diagram of an embodiment of the
`invention that is similar to that shown in FIGS. 6a and 6b,
`45 wherein the input/output ports are disposed between the
`modifying means and dispersive element;
`FIG. 8 is a schematic diagram of a DGE having a
`confiNtration similar to that shown in FIGS. 6a and 6b
`including an optical circulator; and
`FIG. 9 is a schcmatic diagram of a DGE!COADM in
`accordance with the instant invention including a lens hav-
`ing a single port for launching and receiving light from the
`concavc rcflcctor;
`FIG. 9a is a top vie~v showing a lenslet array coupling
`55 input!output optical waveguides to the lens in accordance
`
`5o
`
`with the instant invention;
`FIG. 9b is a top view showing a prior art polarization
`diversity arrangement coupling input/output optical
`~vaveguides to the lens in accordance with the instant
`6o invention;
`
`FIG. 9c is a side view of the prior art polarization diversity
`arrangement shown in FIG. 9b;
`FIG. 9d is a top view showing an alternative arrangement
`(,5 to the optical components shown in FIG. 9b;
`FIG. 9e is a side view of the alternate arrangement shown
`in FIG. 9d;
`
`Petitioner Ciena Corp. et al.
`Exhibit 1003-15
`
`

`

`US 6,498,872 B2
`
`5
`FIG. 9fis a top view showing an asymmetric offset of the
`input/output optical waveguides with respect to the optical
`axis of the lens, in accordance with the instant invention;
`FIG. 111 is a schematic diagram of another embodiment of
`a DGE!COADM in accordance with the invention;
`FIG. 11 is a schematic diagram of the preferred embodi-
`ment of a COADM in accordance with the instant invention;
`and,
`FIG. 12 is a schematic diagram of a COADM in accor-
`dance with the instant invention, wherein an asymmetric
`arrangement of the input/output optical waveguides comple-
`ments the angular displacement provided by a MEMS
`element.
`
`DETAILED DESCRIPTION
`
`Referring now to FIG. 1, an optical device for rerouting
`and modifying an optical signal in accordance with the
`instant invention is shown that is capable of operating as a
`Dynamic Gain/Channel Equalizer (DGE) and/or a Config-
`urable Optical Add/Drop Multiplexer (COADM).
`The optical design includes a diffraction element
`disposed between and at a focal plane of identical elements
`ll0a and 1111b having optical power, respectively. Two ports
`1112a and 1112b are shown at an input/output end with
`bi-directional arrows indicating that light launched into port
`1112a can be transmitted through the optical device and can
`be reflected backward to the input port from which it was
`launched 102a, or alternatively, can be switched to port 102b
`or vice versa in a controlled manner, llae input/output ports
`102a and 102b are also disposed about one focal plane away
`from the element having optical power ll0a to which they
`are optically coupled. Although only two input/output ports
`are shown to facilitate an understanding of this device, a
`plurality of such pairs of ports is optionally provided. At
`other end of the device, modifying means 150 for modifying
`at least a portion of the light incident thereon is provided
`about the focal plane of the element having optical power
`llOb.
`Since the modifying means and/or dispersive element are
`generally dependent upon polarization of the incident light
`beam, lighl having a known polarization state is provided to
`obtain the selected switching and/or attenuation. FIGS. 2a
`and 2b illustrate two different embodiments of polarization
`diversily arrangements for providing light having a known
`polarization state, for use with the DGEiCOADM devices
`described herein. The polarization diversity arrangement,
`which is optionally an array, is optically coupled to the input
`and output ports.
`Referring to FIG. 2a an embodiment of a front-end
`micro-optical component 1!)5 for providing light having a
`known polarization is shown having a fibre tube 1!1’7, a
`microlens 112, and a birefringent element 114 for separating
`an input beam into two orthogonal polarized sub-beams. At
`an output end, a half waveplate 116 is provided to rotate the
`polarization of one of the beams by 90° so as to ensure both
`beams have a same polarization state e.g., horizontal. A glass
`plate or a second waveplate 118 is added to the fast axis path
`of the crystal 114 to lcsscn thc cffccts of Polarization Modc
`Dispersion (PMD) induced by the difference in optical path
`length along the two diverging paths of crystal 114.
`FIG. 2b illustrates an alternative embodiment to that of
`FIG. 2a, wherein two birefringent elements l14a, l14b have
`a half waveplate 116a disposed therebetween; here an alter-
`nate scheme is used to make the path lengths through the
`birefringent materials substantially similar. Optionally, a
`third waveplate 119 is provided for further rotating the
`polarization state.
`
`Although, FIGS. 2a and 2b both illustrate a single input
`beam of light for ease of understanding, the front end unit
`105 is capable of carrying many more beams of light
`therethrough, in accordance with the instant invention (i.e.,
`5 can be designed as an array as described above).
`FIGS. 3a-3b, 3c-3d, 4, and 5, each illustrate a different
`cmbodimcnt of the modifying mcans for use with thc
`DGE!COADM devices described herein. Each of these
`cmbodimcnts is dcscribcd in morc detail bclow. Notc that
`1,3 the modifying means are generally discussed with reference
`to FIG. 1. However, although reference is made to the
`dispersive element 120 and elements having optical power
`ll0a and ll0b, these optical components have been omitted
`from FIGS. 3a-3b, 3c-3d, 4, and 5 fur clarity.
`
`~ s Referring to FIGS. 3a and 3b a schematic diagram of the
`modifying means 150 is shown including a liquid crystal
`array 130 and a reflector 140. The reflector includes first and
`second polarizing beam splitters 144 and 146, and reflective
`surface 142.
`
`2o When the device operates as a COADM, each pixel of the
`liquid crystal array 130 is switchable between a first state
`e.g., an "ON" state shown in HG. 3a, wherein the polar-
`ization of a beam of light passing therethrough is unchanged
`(e.g., remains horizontal), and a second state e.g., an "OFF"
`25 slate shown in lqG 3b, ~vherein the liquid crystal cell rotales
`the polarization of a beam of light passing therethrough 90°
`(e.g., is switched to vertical). The reflector 140 is designed
`to pass light having a first polarization (e.g., horizontal) such
`that beam of light launched from port 102a is reflected back
`3,3 to the same port, and reflect light having another polarization
`(e.g., vertical) such that a beam of light launched from port
`102a is switched to port 102b.
`When the device operates as a DGE, each liquid crystal
`cell is adjusted to provide phase retardations between 0 to
`35 180°" For a beam of light launched and received from port
`102a, 0% attenuation is achieved when liquid crystal cell
`provides no phase retardation and 100% attenuation is
`achieved ~vhen the liqnid crystal cell provides 180° phase
`retardation. Intermediate attenuation is achieved when the
`4o liquid crystal cells provide a phase retardation greater than
`0 and less than 180°. In some DGE applications, the reflector
`140 includes only a reflective surface 142 (i.e., no beam
`splitter).
`Preferably, the liquid crystal array 130 has at least one
`45 row of liquid crystal cells or pixels. Eor example, arrays
`comprising 64 or 128 independently controlled pixels have
`been found particularly practical, but more or fewer pixels
`are also possible. Preferably, the liquid crystal cells are of
`the twisted nematic type cells, since they typically have a
`s0 very small residual birefringence in the "ON" state, and
`conscqucntly allow a vcry high contrast ratio (>35 dB) to bc
`obtained and maintained over the wavelength and tempera-
`ture range of interest. It is also preferred that the inter-pixel
`areas of thc liquid crystal array 130 arc covcrcd by a black
`55 grid.
`FIGS. 3c and 3d are schematic diagrams analogous to
`FIGS. 3a and 3b illustrating an alternate form of the modi-
`fying mcans 150 discusscd above, whcrcin thc rcflcctor 140
`includes a double Glan prism. The arrangement shown in
`6o FIGS. 3c and 3d is preferred over that illustrated in FIGS. 3a
`and 3b, sincc thc rcspccfivc position of thc two-sub bcams
`emerging from the polarization diversity arrangement (not
`sho,aar) does not change upon switching.
`Note that in FIGS. 3a-3d, the dispersion direction is
`(~5 perpendicular to the plane of the paper. For exemplary
`purposes a single ray of light is shown passing through the
`modifying means 150.
`
`Petitioner Ciena Corp. et al.
`Exhibit 1003-16
`
`

`

`US 6,498,872 B2
`
`7
`FIGS¯ 4a and 4b are schematic diagrams showing another
`eurbodiment of the modit~ing means 150, wherein a bire-
`fringent crystal 152 is disposed before the liquid crystal
`array I30. A beam of light having a predetermined polar-
`ization state launched from port 102a is dispersed into
`sub-beams, which are passed through the birefringent crystal
`152. The sub-beams of light passing through the birefringent
`crystal 152 remain unchanged with respect to polarization.
`The sub-beams of light are transmitted through the liquid
`crystal array 1311, where they are selectively modified, and
`reflected back to the birefringent crystal 152 via reflective
`surfacc 142. If a particular sub-bcam of light passcs through
`a liquid crystal cell in an "OFF" state, as shown in FIG. 4a,
`thcn thc polarization thcrcof will bc rotatcd by 90° and thc
`sub-beam of light will be refracted as it propagates through
`the birefringent crystal 152 before being transmitted to port
`1112b. If the sub-beam of light passes through a liquid crystal
`cell in an "ON" state, as shown in FIG. 4b, then the
`polarization thereof will not be rotated and the sub-beam of
`light will be transmitted directly back to port 1112a. A half
`wave plate 153 is provided to rotate the polarization of the
`refracted sub-beams of light by 90° to ensure that both
`reflected beams of light have a sanre polarization state.
`FIG. 5 is a schematic diagram of another embodiment of
`the modifying means 1511 including a micro electromechani-
`cal switch (MEMS) 155, which is particularly uscful whcn
`the device is used as a DGE. A beam of light having a
`prcdctcrmincd polarization statc launchcd from port 1112a is
`dispersed into sub-beams and is passed through a birefrin-
`gent element 156 and quarter waveplate 157. The birefrin-
`gent element 156 is arranged not to affect the polarization of
`the sub-beam of light. After passing through the quarter
`waveplate 157, the beam of light becomes circnlarly polar-
`ized and is incident on a predetermined reflector of the
`MEMS array 155. The reflector reflects the sub-beam of
`light incident thereon back to the quarter waveplate. The
`degree of attenuation is based on the degree of deflection
`provided by the reflector (i.e., the angle of reflection)¯ After
`passing through the quarter waveplate 157 for a second time,
`the attenuated sub-beam of light will have a polarization
`state that has been rotated 90° from the original polarization
`state. As a result the attenuated sub-beam is refracted in the
`birefringent element 156 and is directed out of the device to
`port 102b. A half wave plate 158 is provided to rotate the
`polarization of the refracted sub-beams of light by 90°.
`Of course, other modifying means 151) including at least
`one optical element capal~le of modifying a property of at
`least a portion of a beam of light and reflecting the modified
`beam of light back in substantially the same direction from
`which it originated are possible¯
`Advantageously, each of the modifying means discussed
`above utilizes an arrangement wherein each spatially dis-
`persed beam of light is incident thereon and reflected
`therefrom at a 90° angle¯ The 90° angle is measured with
`respect to a plane encompassing the array of modifying
`elements (e.g., liquid crystal cells, MEMS refleclors).
`Accordingly, each sub-beam of light follows a first optical
`path to the modifying means where it is selectively s~vitched
`such that it is rcflcctcd back along thc samc optical path, or
`alternatively, along a second optical path parallel to the first.
`The lateral displacement of the input and modified output
`bcams of light (i.c., as opposcd to angular displaccmcnt)
`allows for highly efficient coupling between a plurality of
`input/output waveguides. For example, the instant invention
`is particular uscful whcn thc input and output ports arc
`located on a same multiple bore tube, ribbon, or block¯
`In order to ma