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`USOORE42673E
`
`(19) United States
`
`(12) Reissued Patent
`(10) Patent Number:
`US RE42,678 E
`Wilde et at.
`
`Sep. 6, 2011
`(45) Date of Reissued Patent:
`
`(54) RECON FIGURABLE OPTICAL ADD-DROP
`MULTIPLEXERS WITII SERVO CONTROL
`AND DYNAMIC SPECTRAL P0\VI£R
`MANAGEMENT CAPABILITIES
`
`(T5)
`
`Inventors: Jeffrey I’. Wilde. Morgan Hill. (‘A (US):
`Joseph E. Davis. Morgan IIiIL (“A (US)
`
`(T3) Assignee:
`
`(.Tspella Phutentcs. Inc.. San Jose. (.‘A
`(US)
`
`(2]) Appl.No.: ”$15,930
`
`(22)
`
`Filed:
`
`Jun. 15.2010
`Related US. Patent Documents
`
`Re. 39,397
`Nov. 14. 2006
`I 110122586
`Dec. 3 l, 2004
`
`Reissue of:
`(64)
`’atent No;
`Issued:
`App}. No.:
`Filed:
`Which is a Reissue ol‘:
`(64)
`Patent No.:
`Issued:
`Appl. No .:
`Filed:
`US. Applications:
`(60) vaisional application No. 60f277.2|?. filed on Mar.
`19. 2001.
`
`6‘625546
`Sep. 23, 2003
`091938.426
`Aug. 23. 2001
`
`(SI)
`
`lnt.(.‘l.
`(2006.01 }
`6023 6/28
`3851'24: 38501385823851.7131
`(52) 11.8.0.
`..
`(58)
`Field ofclassmeation Search
`385124.
`3851’] I. 3?. 34
`See application file for con'tplete search history.
`
`
`
`(56)
`
`References Cited
`
`
`
`US. I’.'\'1'L"N'1' DOL'UMEN'I'S
`359.39
`5.401.540 A
`5-1995 Patelel a1.
`359-1981
`5.639.790 A ‘
`5.1997 Neukenmms etal.
`5.745.321 A
`4-1998 Ford el al.
`........
`.. 359-130
`36944.12
`5.835.458 A ‘
`Ii 1993 Bisehelelal.
`
`53260.83 A "
`‘J. [999 Tomlinson
`385.18
`385-24
`5.924.207 A ‘
`[01999 Aksyuk et al.
`
`359224
`22000 Michallcek elal
`6.028.689 A
`
`332001 Aksyuk et al.
`.. 398-‘9
`6.204.946 Bl ‘
`385-24
`0.205.269 BI ‘
`3 2001 Manon
`
`385318
`6.222.954 Bl“
`4-2001 Rim ..
`6.253.135 Bl
`2.2001 Wade
`385.32
`
`6.256.430 HI
`7 2001
`Jin el :11.
`385-13
`6.263J35 BI ‘
`732001 Wade
`385 3'."
`6.289J55 BI ‘
`9.2001 Wade
`385.3?
`
`6.302.557 [3|
`[02001 Ford
`359-130
`(Continued)
`
`Brian M Ilealy
`Primary limmt'ner
`(74) glimmer. Agent. or Firm —- Harry N. Young
`
`ABSTRACT
`(57;
`This invention provides a novel \vavelengtlt-separating-rout-
`ing (WSR) apparatus that uses a diil‘raction grating, to sepa—
`rate a mold-wavelength optical signal by wavelength into
`multiple spectral characters. which are then liucttsed onto an
`array talcum-spending channel Inicmmirrors. The channel
`microt‘nirrors are individually controllable and continuously
`pivolahle to rellect the spectral channels into selected output
`ports. As such. the inventive WSR apparatus is capable of
`routing the spectral channels on a channel—hy—ehannel basis
`and coupling any spectral chatmel into any one of the output
`ports. The WSR apparatus of the present invention may be
`lilrther equipped with servo-control and spectra] power-man-
`agement capabilities. therebyr maintaining the coupling elli—
`ciencies ot‘ the spectral channels into the output ports at
`desired values. the WSR apparatus of the present invention
`can be used to construct a novel class of dynamicallyr recon-
`figurable optical add-drop multiplexers (0r\1)Ms) for WUM
`optical networking applications.
`
`67 Claims, 12 Drawing Sheets
`
`
`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1001, Page 1
`Exhibit 1001, Page 1
`
`

`

`US RE42,678 E
`Page 2
`
`6.4 [8.2 50
`6.4 98 .8 'r‘ 2
`6.5615 74
`(1.600.851
`6.625.346
`6.63 I .222
`6.6134 .3 10
`
`US. PA'I'IIEN'I‘ DOCUMENTS
`BI“
`'.I‘"2002 Corbosjcrocl n1.
`.
`B2
`[22002 Doucvitch er al.
`
`Bl
`5.2003 Ma of. al.
`
`HZ
`T2003 Aksyuk er al.
`I412 "
`9-2003 Wilde ........
`Bl
`{0-2003 Wagcncr cl al.
`HI
`{0:200} Fun] at :1l.
`
`
`6.8 I U. I 69 H2
`6.893.348 B2
`l32
`6.939.921
`I“.
`RI?39.3')7
`I32
`7. t83.fi33
`200 2:0 I 3 mm
`Al‘
`20033004 34?].
`."\| *
`
`“
`
`385324
`lhauwitch
`[Ll-"2004
`.
`.. 385:3?
`S. 2005 Morozov cl al.
`359-290
`1-2006 lkmslcin cl a1.
`
`.. 385-‘24
`[132006 Wilde cl :Il.
`______
`
`257-628
`2: 2007 Danclnnn at (:1.
`
`9.2002 (ianellcl :lI.
`385-24
`3:200} Balscrc! :IJ.
`359-034
`
`" cited by examiner
`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1001, Page 2
`Exhibit 1001, Page 2
`
`

`

`Sen. 6, 2011
`
`Sheet 1 or 12
`
`US RE42,678 E
`
`
`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1001, Page 3
`Exhibit 1001, Page 3
`
`

`

`103
`
`
`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1001, Page 4
`Exhibit 1001, Page 4
`
`

`

`US. Patent
`
`Sep. 6, 2011
`
`Sheet 3 of12
`
`US RE42,678 E
`
`Amd
`
`.)In-
`
`LO
`n!
`C)
`
`88’
`:53
`CD
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`2
`m?
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`5"HI
`9.3.9
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`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1001, Page 5
`Exhibit 1001, Page 5
`
`

`

`US. Patent
`
`Sep. 6. 2011
`
`Sheet 4 of 12
`
`US RE42,678 E
`
`Collimated Beam
`
`
`
`(In-Axis Coupling
`Wag)
`
`\
`
`Fiber
`
`GRIN Lens
`
`/
`
`Collimated Beam
`
`
`
`
`
`Off-Axis Coupling
`(9: 0.2 deg)
`
`Fig. 1D
`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1001, Page 6
`Exhibit 1001, Page 6
`
`

`

`US. Patent
`
`881). 6, 2011
`
`Sheet 5 of 12
`
`US 1113424578 E
`
`
`
`Fig. 2A
`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1001, Page 7
`Exhibit 1001, Page 7
`
`

`

`US. Patent
`
`Sep. 6, 2011
`
`Sheet 6 of 12
`
`US RE42,678 E
`
`101
`
`220
`
`260
`
`270
`
`110-1
`110
`
`110-2
`
`
`
`Fig. 23
`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1001, Page 8
`Exhibit 1001, Page 8
`
`

`

`US. Patent
`
`Sep. 6. 2011
`
`Sheet 7 of12
`
`US RE42,678 E
`
`Fm_—"'__E>"“"""_""l
`
`260
`
`2'10
`
`1 10
`
`
`
`Fig. 20
`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1001, Page 9
`Exhibit 1001, Page 9
`
`

`

`Sheet 8 of 12
`
`.1
`
`E
`
`
`
`Fig. 3
`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1001, Page 10
`Exhibit 1001, Page 10
`
`

`

`US. Patent
`
`Sep. 6. 2011
`
`Sheet 9 of12
`
`US RE42,678 E
`
`400
`
`410
`
`WSR Apparatus
`
`
`
`
`
`Ehannel Micromirrors
`- _ _ - _l -‘
`
`|
`
`440
`
`Fig. 4A
`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1001, Page 11
`Exhibit 1001, Page 11
`
`

`

`US. Patent
`
`Sep. 6. 2011
`
`Sheet 10 of 12
`
`US RE42,678 E
`
`450
`
`480
`
`WSR Apparatus
`
`’3---
`
`485
`S---
`
`- :— Channel 1:—AI.Collimamr- 1—.—
`
`
`Fig.4B
`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1001, Page 12
`Exhibit 1001, Page 12
`
`

`

`US. Patent
`
`Sep. 6. 2011
`
`Sheet 11 of 12
`
`US RE42,678 E
`
`570
`
`550
`
`510
`
`540-N
`
`540-1
`
`500
`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1001, Page 13
`Exhibit 1001, Page 13
`
`

`

`US. Patent
`
`Sep. 6,20”
`
`Sheet 12 of 12
`
`US RE42,678 E
`
`570
`
`650
`
`650-1
`
`SecondWSR-S
`
`
`660~M
`
`640-1
`
`610
`
`
`
`FirstWSR—S
`
`
`520
`
`640-N
`
`600
`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1001, Page 14
`Exhibit 1001, Page 14
`
`

`

`US RE42.6?8 E
`
`1
`RECONFIGU RABLE OPTICAL ADD-DROP
`MUI.'l'lPI.F.XERS WITH SERVO CONTROL
`AND DYNAMIC SPECTRAL POWER
`MANAGEMENT CAPABILITIES
`
`Mattcrenclosed in heavy brackets [ ]appears in the origi—
`nal patent but forms no part of the first and this reissue
`specification; matter printed in italics indicates the addi-
`tions made by the first reissue. Mutter enclosed in double
`heavy brackets [[ ]] appears in the first reissue patent
`but forms no part of this "tissue specification: matter
`printed in bold face indicates the additions made by this
`reissue.
`
`CROSS-REFERENCE TO RELATED
`APPLICATIONS
`
`This application claims priority of US. Provisional Patent
`Application No. GOIZTTJIT. filed Mar. 19. 2001 which is
`incorporated herein by reference.
`
`FIELD OF THE INVENTION
`
`This invention relates generally to optical communication
`systems. More specifically.
`it relates to a novel class ol‘
`dynamically reconfigurable optical add—drop multiplexers
`(OADMS) for wavelength division multiplexed optical net-
`working applications.
`BACKGROUND
`
`As fiber-optic conununication networks rapidly spread
`into every walk ofmodern life. there is a growing demand for
`optical components and subsystems that enable the liber-
`optic communications networks to be increasingly scalable.
`versatile. robust. and cost-effective.
`Contemporary fiber-optic conuntmications networks com-
`monly employ wavelengthdivision multiplexing {WDM}. for
`it allows multiple information (or data) channels to be simul-
`taneously transmitted on a single optical fiber by using dif-
`ferent wavelengths and thereby significantly enhances the
`infonnationmbandwidth ofthe fiber. The prevalence of WUM
`technology has made optical add-drop multiplexers indis-
`pensable building blocks of modern fiber-optic communica-
`tion networks. An optical add-drop multiplexer (OADM)
`serves to selectively remove (or drop) one or more wave-
`lengths from a multiplicity ofwavelengths on an optical fiber.
`hence taking away one or more data chaiutels from the tra [lie
`stream on the fiber. It funher adds one or more wavelength
`back onto the fiber. thereby inserting new data channels in the
`same stream oftratlic. As such. an DADM makes it possible
`to launch and retrieve multiple data channels (each chame-
`tcrized by a distinct wavelength) onto and from an optical
`fiber respectively. without disrupting the overall tratfic flow
`along the fiber. Indeed. careful placement of the OADMs can
`dramatically improve an optical communication network‘s
`flexibility and robustness. while providing significant cost
`advantages.
`Conventional OADMs in the an typically employ multi-
`plcxersldemultiplexers (cg. waveguide grating routers or
`anayed-wavcguide
`gratings).
`tunable
`filters.
`optical
`switches. and optical circulators in a parallel or serial archi-
`tecture to accomplish the add and drop functions.
`In the
`parallel architecture. as exemplified iii U.S. Pat. No. 5.974.
`20?. a demultiplexer (e.g.. a waveguide grating router) first
`separates a multi-wavelength signal into its constituent spoon
`tral components. A wavelength switchingt'routing means
`
`1t:
`
`2t]
`
`I.) '4':
`
`30
`
`35
`
`2
`(e.g.. a combination ot‘optical switches and optical circula-
`tors) then serves to drop selective wavelengths and add others.
`Finally, a multiplexer combines the remaining (i.e.. the pass-
`through) wavelengths into an output multi-wavelength opti-
`cal signal. In the serial architecture. as exemplified in US.
`Pat. No. 6.205.269. tunable tillers (e.g.. Bragg fiber gratings)
`in combination with optical circulators are used to separate
`the drop wavelength from the pass-through wavelengths and
`subsequently launch the add channels into the pass-through
`path. And if multiple wavelengths are to be added and
`dropped. additional multiplexers and demultiplexcrs are
`required to demultiplex the drop wavelengths and multiplex
`the add wavelengths. respectively. Irrespective of the under-
`lying architecture. the OADMs currently in the art are char-
`' actcristically high in cost. and prone to significant optical loss
`accumulation. Moreover. the designs of these OADMS are
`such that it is inherently diflicult to reconfigure them in a
`dynamic fashion.
`US. Pat. No. 6.204.946 to Askytlk et al. discloses an
`OADM that makes use of free-space optics ina parallel con-
`struction.
`In this case. a mum-wavelength optical signal
`emerging from an input port is incident onto a ruled diffrac-
`tion grating. The constituent spectral channels thus separated
`are then focused by a focusing lens onto a linear array of
`biliary micromachined mirrors. Liach micromirror is config-
`ured to operate between two discrete states. such that it either
`retrofits its corresponding spectral channel back into the input
`port as a pass-through channel. or directs its spectral channel
`to an output port as a drop channel. As such. the pass-through
`signal (i.e.. the combined pass-through channels) shares the
`same input port as the inpttt signal. An optical circtllator is
`therefore coupled to the input port. to provide necessary rout-
`ing of these two signals. Likewise. the drop channels share the
`output port with the add channels. An additional optical cir-
`culator is thereby coupled to the output port. from which the
`drop channels exit and the add channels are introduced into
`the output ports. The add channels are subsequently com-
`bined with the pass—through signal by way of the dillractioit
`grating and the binary micromirrors.
`Although the aforementioned OADM disclosed byAskyuk
`et al. has the advantage of performing wavelength separating
`and routing in free space and thereby incurring less optical
`loss. it suffers a number of limitations. First. it requires that
`the pass-through signal share the same portttiber as the input
`signal. An optical circulator therefore has to be implemented.
`to provide necessary routing of these two signals. Likewise.
`all the add and drop channels enter and leave the GADM
`dmulgh the same output pon. hence the need for another
`optical circulator. Moreover. additional means must be pro—
`vided to multiplex the add channels before entering the sys-
`tem and to demultiplex the drop channels afier exiting the
`system. This additional multiplexingfdemultipleit ing require-
`tnent adds more cost and complexity that can restrict the
`versatility of the OAIJM tints-constructed. Second. the opti-
`cal circulators implemented in this OADM for various rout-
`ing purposes introduce additional optical losses. which can
`accumulate to a substantial amount. 'Ihird. the constituent
`optical components must be in a precise aligin'nent. in order
`for the system to achieve its intended purpose. There are.
`however. no provisions provided for maintaining the requisite
`aliglunent: and no mechanisms implemented for overcoming
`degradation in the alignment owing to cnvironm ental eliects
`such as thermal and mechanical disturbances over the course
`ot'opcration.
`U .8. Pat. No. 5.906.133 to Tomlinson discloses an DADM
`that makes use of a design similar to that of Aksyuk et al.
`There are input. output. drop and add ports implemented in
`
`40
`
`45
`
`50
`
`55
`
`do
`
`63
`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1001, Page 15
`Exhibit 1001, Page 15
`
`

`

`US RE42.6?8 E
`
`3
`this case. By positioning the four ports in a specific arrange-
`ment. each micromirror. notwillnitanding switchable between
`two discrete positions. either reflects its corresponding chan-
`nel (coming from the input port) to the output port. or con~
`coinita ntly rellects its channel to the drop port and an incident
`add channel to the output port. As such. this OADM is able to
`perform both the add and drop fimctions without involving
`additional optical components (such as optical circulators and
`in the system of theAksyult et al.). However. because a single
`drop port is designated for all the drop channels and a single
`add port is designated for all the add channels. the add chan~
`ncls would have to be multiplexed before entering the add
`port and the drop channels likewise need to be demultiplexed
`upott exiting from the drop pon. Moreover. as in the case of
`Askyuk el al.. there are no provisions provided for maintain—
`ing requisite optical alignment in the system. and no mecha-
`nisms implemented for combating degradation in the align-
`ment due to environmental ell'ects over
`the course 01‘
`operation.
`As such. the prevailing drawbacks suffered by the OADMs
`currently in the art are summarized as follows:
`1)Tlte wavelength routing is intrinsically static. rendering it
`difficult to dynamically reconfigure these DADMs.
`2) Add andi'or drop channels often need to be multiplexed
`andfor demultiplexed. thereby imposing additional com~
`plexity and cost.
`3) Stringent fabrication tolerance and painstaking optical
`alignments aremquired. Moreover. theoptica] alignment is
`not actively maintained. rendering it susceptible to envi—
`ronmental efiects such as thermal and mechanical distur-
`bances over the course ofoperation.
`4) In an optical communication network. OADMs are typi—
`cally in a ring or cascaded configuration. In order to mili—
`gate the interference atnongst OADMS. which often
`adversely affects the overall perfomlanee ot'the network. it
`is essential that the power levels of specll'ctl channels enter—
`ing and exiting each OADM be managed in a systetnatic
`way. for instance. by introducing power (or gain) eq ualiza-
`tion at each stage. Such a power equaliyation capability is
`also needed for compensating litrnonunilhrm gain caused
`by optical amplifiers (cg. erbittm doped fiber amplifiers)
`in the network. There lacks. however. a systematic and
`dynamic management ofthe power levels 0 f various spec—
`tral channels in these OADMs.
`loss funher
`5) The inherent high cost and heavy optical
`impede the wide application ol'lhcse OADMs.
`In view of the loregoing. there is an urgent need in the art
`for optical add-drop multiplexers that overcome the afore-
`mentioned shortcomings. in a simple. effective. and economi—
`cal construction.
`
`SUMMARY
`
`The present invention provides a wavelength-separating-
`routing (WSR) apparatus and method which employ an array
`ol'l'lber collimators serving as an input port and a plurality of
`output ports: a wavelength-separator: a beam-focuser'. and an
`away ofchanncl micromirrors.
`in operation. a multimwavelength optical signal emerges
`front the input port. The wavelength-separator separates the
`mold-wavelength optical signal into multiple spectral chan-
`nels. each character-ind by a distinct center wavelength and
`associated bandwidth. The bezun—lbcuscr focuses the spectral
`channels into corresponding spectral spots. The channel
`micromirrors are positioned such that each channel micro-
`mirror receives one of the spectral channels. The channel
`micromirrors are individually controllable and movable. cg.
`
`or
`
`1t:
`
`2t]
`
`I.) '4':
`
`30
`
`40
`
`55
`
`do
`
`4
`continuously pivotablc (or rotatable). so as to reflect the spec-
`tral channels into selected ones of the output ports. As such.
`each chamte] nticromirror is assigned to a specific spectral
`channel. hence the name “channel micromirrur”. And each
`output port may receive any number ol’the reflected spectral
`channels.
`feature of the channel micromirrors in the
`A distinct
`present invention. in contrast to those used in the prior art. is
`that the motion. e.g.. pivoting (or rotation). ofeach channel
`microntin'or is under analog control such that
`its pivoting
`angle can be continouously adjusted. This enables each chan—
`nel micromirror to scan its corresponding spectral channel
`across all possible output ports and thereby direct the spectral
`channel to any desired output ports.
`In the WSR apparatus of the present invention. the wave—
`length-separator may be provided by a ruled diffraction grat-
`ing. a holographic dilli'action grating. an echelle grating. a
`curved diffraction grating. a dispersing prism. or other wave-
`length—separating means known in the art. The beam—I'ocuser
`may be a single lens. an assembly o l‘ lenses. or other beam—
`focusing means known in the an. The channel micromirrors
`may be provided by silicon micromachined mirrors. reflec-
`tive ribbons (or membranes). or other types ofbcam-dellect-
`ing means known in the art. And each channel micromirror
`may be pivotable about one or two axes. The fiber collimators
`serving as the input and output ports may be arr-.mged in a
`one-dimensional or two-dimensional array. In the latter case.
`the channel micromin'ors must be pivotable biaxially.
`’l'hc WSR apparatus of the present invention may further
`comprise an array ofcollimator-alignment minors, in optical
`communication with the wavelength-separator and the fiber
`collimators. for adjusting the alignment of the input multi-
`wavelcngth signal and directing the spectral channels into the
`selected output ports by way of angular control of the colli-
`mated beams.
`[Each collimator-alignment mirror may be
`rotatable about one or two axes. The collimator-alignment
`mirrors may be arranged in a one~dimensional or two-dimen-
`sional array. First and second arrays of imaging lenses may
`additionally be optically interposed between the collimator-
`aligiuncnt mirrors and the fiber collimators in a telecentrie
`arrangement.
`thereby “imaging“ the collimator~alignment
`mirrors onto the corresponding fiber collimators to ensure an
`optimal alignment.
`The WSR apparatus of the present invention may further
`include a servo-control assembly. in communication with the
`channel tnicrotnirrors and the output ports. The servo-control
`assembly serves to monitor the power levels of the spectral
`channels coupled into the output ports and further provide
`control ot'thc channel micromirrors on an individual basis. so
`as to maintain a predetemtincd coupling elliciency of each
`spectral channel
`in one of the output ports. As such.
`the
`servo-control assembly provides dynamic control of the cott-
`pling of the spectral channels into the respective output ports
`and actively manages the power levels of the spectral chart-
`nels coupling into the output ports. (if the WSR apparatus
`inclttdcs an array of collimator-alignment mirrors as
`described above. the servo-control assembly may addition-
`ally provide dynamic control ol' the collimator-alignment
`mirrors.) Moreover. the utilisation of such a servo-control
`assembly effectively relaxes the requisite fabrication toler-
`ances and the precision ot‘optica] alignment during assembly
`of a WSR apparatus of the present invention. and further
`enables the system to correct for shift in optical alignmcnt
`over the course ofoperation. A WSR apparatus incorporating
`a servo-control assembly thus described is termed a WSRAS
`apparatus. thereinaficr in the present invention.
`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1001, Page 16
`Exhibit 1001, Page 16
`
`

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`q
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`US RE42.6?8 E
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`the WSR-S (or WSR) apparatus of the
`Accordingly.
`present invention may be used to construct a variety ofoptical
`devices. including a novel class of dynamically reconfig-
`urable optical add-drop multiplexers (OADMs), as exempli-
`lied in the following embodiments.
`One embodiment of an OADM of the present invention
`comprises an aforementioned WSR-S (or WSR) apparatus
`and an optical cotnbiner.
`'Ihe output ports of the WSR-S
`apparatus include a pass-through port and one or more drop
`ports. each carrying any number of the spectral channels. The
`optical combiner is coupled to the pass-through port. serving
`to combine the pass-through channels with one or more add
`spectral channels. The combined optical signal constitutes an
`output signal ot'the system. The optical combiner may be an
`le {N22} broadband fiber-optic coupler.
`for instance.
`which also serves the purpose of multiplexing a multiplicity
`of add spectral channels to be coupled into the system.
`In another embodiment ofan OADM of the present inven-
`tion. a first WSR—S (or WSR) apparatus is cascaded with a
`second WSR-S (or WSR'} apparatus. The output ports of the
`lirst WSR-S (or WSR} apparatus include a pass‘through port
`and one or more drop ports. The second WSR-S (or WSR)
`apparatus includes a plurality of input ports and an exiting
`port. The configuration is such that the pass-tlu‘ough channels
`from the first WSR-S apparatus and one or tnore add channels
`are directed into the input ports of the second WSR-S appa-
`ratus. and consequently multiplexed into an output multi-
`wavelength optical signal directed into the exiting port ofthe
`second WSR-S apparatus. That is to say that in this embodi-
`ment. one WSR-S apparatus (e.g.. the first one) effectively
`performs a dynamic drop function. whereas the other WSR-R
`apparatus (c.g.. the second one) carries out a dynamic add
`function. And there are essentially no fundamental restric-
`tions on the wavelengths that can be added or dropped. other
`than those imposed by the overall communication system.
`Moreover. the underlying OADM architecture thus presented
`is intrinsically scalable and can be readily extended to any
`number of the WSR-S (or WSR) systems. if so desired for
`performing intricate add and drop functions in a network
`enviromnent.
`Those skilled in the art will recognize that the aforemem
`tioned embodiments provide only two ofmany embodiments
`of a dynamically reconfigurable OADM according to the
`present invention. Various changes. substitutions. :utd alter-
`nations can be ntade herein. without departing front the prin-
`ciples and the scope of the invention. Accordingly. a skilled
`artisan can design an OADM in accordance with the present
`invention. to best suit a given application.
`All in all. the OADMs of the present invention provide
`many advantages over the prior art devices. notably:
`1) By advantageously employing an array ofchannel micro-
`mirrors that are individually and continuously conu‘ol-
`lable, an OADM of the present
`invention is capable of
`routing the spectral channels on a channel-by-cltannel
`basis and directing any spectral channel into any one of the
`output ports. As such. its underlying operation is dynami—
`cally reconfigurable. and its underlying architecture is
`intrinsically scalable to a large number of channel counts.
`2) The add aitd drop spectral channels need not be multi-
`plexed and demultiplexed before entering and allcr leaving
`the (JADM respectively. And there are not fundamental
`restrictions on the wavelengths to be added or dropped.
`3) The coupling of die spectral channels into the output ports
`is dynamically controlled by a servo-control assembly.
`rendering the OADM less susceptible to environmental
`elleets (such as tltemtal and mechanical disturbances) and
`therefore more robust in perfonnance. By maintaining an
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`optimal optical alignment. the optical losses incurred by
`the spectral charmels are also significantly reduced.
`4) The power levels of the spectral chatutcls coupled into the
`output pons can be dynamically managed according to
`demand. or maintained at desired values (e.g.. equalized at
`a predetermined value) by way of tile servo-control assem-
`bly. 'ihis spectral power-management capability as an inte-
`gral pan of the OADM will be particularly desirable in
`WI)M optical networking applications.
`5) The Lise of free-space optics provides a simple. low loss.
`and cost-effective construction. Moreover. the utilization
`of the servo-control assembly effectively relaxes the req-
`uisite fabrication tolerances and the precision of optical
`alignment during initial assembly. enabling the OADM to
`be simpler and more adaptable in structure. lower in cost
`and optical loss.
`6)'111c underlying OADM architecture allows a multiplicity
`of the OADMs according to the present invention to be
`readily assembled (e.g., cascaded) tor WDM optical net-
`working applications.
`The novel features ol‘this invention. as well as t he invention
`itself. will be best understood from the following drawings
`and detailed description.
`
`BRIEF DESCRIPTION OF THE FIGURES
`
`1“ 168. 1A- lD show a first embodiment of a wavelength-
`separating-routing (WSR) apparatus according to the present
`invention. and the modeling results demonstrating the pcrl‘on
`tnance ofthe WSR apparatus:
`FIGS. EAQC depict second and third embodiments of a
`WSR apparatus according to the present invention:
`FIG. 3 shows a fourth embodiment of a WSR apparatus
`according to the present invention:
`FIGS. 4A—4B show schematic illustration oftwo embodi—
`ments of a WSR-S apparatus comprising a WSR apparatus
`and a servo-control assembly. according to the present inven-
`tion:
`FIG. 5 depicts an exemplary embodiment of an optical
`add—drop multiplexer (OADM) according to the present
`invention: and
`FIG. 6 shot-vs an alternative embodiment of an OADM
`according to the present invention.
`DETAI LED DESCRIPTION
`
`in this specification attd appending claims. a “spectral
`channel" is characterized by a distinct center wavelength and
`associated bandwidth. Each spectral channel may carry a
`unique infomtation signal. as in WDM optical networking
`applications.
`F If}. IA depicts a lirst embodiment ofa wavelength-sepa-
`rating-routing (WSR) apparatus according to the present
`invention. By way of example to illustrate the general prin-
`ciples and the topological structure ofa wavelength-separat-
`ing-routing (WSR) apparatus of the present invention. the
`WSR apparatus l00 comprises multiple inputt'output ports
`which may be in the fonn ofan array of fiber collimators 1 10.
`providing an input port 1 10-1 and a plurality of output ports
`1 10-2 through I lU-N (N23): a wavelength-separator which
`in one form may bea diifraction grating 1012a beam-focuser
`in the form ofa focusing lens 102; and an array of channel
`micromirrors [03.
`In operation. a multi-wavelength optical signal emerges
`from the input port 1 10-]. The diffraction grating lDl angu-
`larly separates the multi-wavelength optical signal into mul-
`tiple spectral channels. which are in turn focused by the
`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1001, Page 17
`Exhibit 1001, Page 17
`
`

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`US RE42.6?8 E
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`7
`focusing letts 102 into a spatial array of'distincl spectral spots
`(not shown in FIG. 1A) in a one-to-onc correspondence. The
`channel micromirrors 103 are positioned in accordance with
`the spatial array fonned by the spectral spots. suclt that each
`clnmnel micromirror receives one of the spectral channels.
`The channel micromirrors 103 are individually control lablc
`and movable. c.g.. pivotablc (or rotatable) under analog (or
`continuous) control. sttclt that. upon reflection. the spectral
`channels are directed into selected ones of tire output ports
`l 102 through I lO—N by way of the focusing lens 102 and the
`di llraction grating 101 . As such. each channel micromirror is
`assigned to a specific spectral channel. hence the name “chan-
`nel micromirror“. Each output port may receive any number
`of the reflected spectral channels.
`For purposes ot'illustralion and clarity. only a selective low
`(c.g.. three) of the spectral chattncls. along with the input
`multi-wavelength optical signal. are graphically illustrated in
`FIG. IA and the following figures. It should be noted. how-
`ever. that there can be any number ofthc spectral channels in
`a WSR apparatus of the present invention (so long as the
`number ofspcctral channels does not exceed the number of
`channel ntirrors entploycd in the system). It should also be
`noted that the optical beams representing the spectral chan-
`nels shown in FIG. 1A and the following ligures are provided
`for illustrative purpose only. That is. their sizes and shapes
`may not be drawn according to scale. For instance. the input
`ham) and the corresponding dilli'acted beams generally have
`different cross-sectional shapes. so long as the angle of inci-
`dence upon the diffraction grating is not equal to the angle of
`diffraction. as is known to those skilled in the art.
`In the ctuboditncnt of HG.
`lA. it is preferable that the
`difli'acting grating 101 and the channel micromirrors 103 are
`placed respectively at the first and second (i.e.. the front and
`back) focal points (on theopposing sides) ofthe Focusing lens
`102. Such a telecentric anatigetnent allows the chief rays of
`tire focused beants to be parallel to each other and generally
`parallel to the optical axis. In this application. the telecentrie
`configuration furtltcr allows the reflected spectral channels to
`be efficiently coupled into the respective output port s. thereby
`minimizing various translational walk-off effects that may
`otherwise arise. Moreover. the input multi-wavelength opti-
`cal signal is preferably collitnated and circular in cross-sec-
`tion. The corresponding spectral channels diffracted from the
`dilfraction grating 10] are generally elliptical in crossnsec-
`tion: they tnay be of the same size as the input beam in one
`dimension and elongated in the other dimension.
`It is known that the diffraction elliciency of‘a diffraction
`grating is generally polariration-dependent. That is. the dif-
`fraction efficiency of a grating ill a standard ntountittg con-
`figuration may be considerably higher for P-polarizalion that
`is perpendicular to the groove lines on the grating than for
`S-polarization that is orthogonal to P-polarization. especially
`as the number of groove lines (per unit length) increases. To
`mitigate such polariaation-sensitive effects. a quarter-wave
`plate 104 may be optically interposed between the diffraction
`grating HM and the channel micromirrors 103. and preferably
`placed between the diffraction grating [01 and the focusing
`lens [02 as is shown in FIG. 1A. In this way. each spectral
`channel experiences a total of approximately 90-degree rota-
`tiott in polarization upon traversing the quarter-wave plate
`104 twice. (That is. il'a beam of'light has [’-polari;ration with
`first encountering the diffraction grating. it Would have pre—
`dominantly (if' not all) S-polariration upon the second
`encountering. and vice versa.) This ensures that all the spec-
`tral channels incur nearly the same amount of rotmd~trip
`polarization dependent loss.
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`In the WSR apparatus 100 of FIG. IA. the diffraction
`grating 10]. by way of example. is oriented such that the
`focused spots of the spectral channels fall onto the channel
`micromin'ors 103 in a horizontal array. as illusttatcd itt l-‘IG.
`1B.
`11% is a close-up view of the channel
`Depictcd in FIG.
`mieromirrors [[13 shown in the embodiment of FIG. IA. By
`way of example. the chamtcl micromirrors 103 are arranged
`in a one-dimensional array along the x-axis (i.e.. the hor