l|||||||||||||||||||ll||l|||||||||||l||||||||||l|||l||||l||||||l|||ll||l|||
`USUUfiU I. I 884A
`
`[19]
`United States Patent
`|ll] Patent Number:
`6,011,884
`|451 Date of Patent: Jan. 4, 2000
`Dueck et al.
`
`
`
`[54I
`
`[75]
`
`INTEGRATED Bl-I)IRECTIONAI.AX[AI.
`GRADIENT REFRACTIVE
`INIJEXJDIFI‘RAC'I'ION GRATING
`WAVELENGTH DIVISION MULTIPLEXER
`
`Inventors: Roher‘l H. Dlleck. Santa Ana. (.‘alil'_;
`Robert K. Wilde. Mgewttttd, N.Mcx.;
`Boyd V. Hunter; Joseph R.
`Denipewolf, both of Albuquerque,
`NMex.
`
`[Tfil Assignce: LightChip, Inc.. Salem. N.ll.
`
`[2]] App]. No: omitting-t
`[22
`l-‘iled:
`Dec. 13, 1997
`
`ll'tl.C|.-’
`[5]]
`[52] US. Cl.
`
`0028 61128
`................................. 385(24; 385.533; 385.334;
`3858?; 385.314: RISE-49; 385.89; 3.593130;
`3593'131: 372250
`385.524, 33, 34,
`Field of Search
`385.331 14, 49, 39; 359t’130, 131; 372350
`
`[58]
`
`[56]
`
`References Cited
`us. PATENT DOCUMENTS
`
`350.199.“!
`01" 978 'i'rimlinsorl.1ll
`4,lll.524
`..
`. 350.196.]?
`5.! 9?” 'I‘omlinson. Ill
`4.153.330
`. 35Ut'9f).l‘.i
`
`4.31080 Kolta yashi
`4. 198.1 I ?
`. 350.196.”
`(itll 98]
`'i'angonun
`4.224.201)
`. 3Sllfilf).l‘.l
`2.." 98] Colombim
`4.39.464
`
`350.328
`I1.-" 98]
`'I‘omlinsort. Ill
`4.299.488
`. 35lli‘lf).l9
`8r'1982 Palmer ..........
`4.343.532
`
`of 083 Ludman et al.
`4.381955
`350,996.19
`..
`1W1984 Kapany el al.
`4,479.00?
`
`..
`6} 985 large at al.
`4.522.452
`4f198t> Flrtmand el all.
`4,583.820
`I1;f 986 lande et a].
`4.622.562
`
`12." 080 Dantmann ct al.
`4,!221’JIJ0‘J
`
`.. 3541323. If)
`U198? Reule
`4.63-1.25
`3503i). [9
`2f 98'?
`liussard ct al.
`4.643.5I9
`35fl.-'9I‘s.l ‘J
`SIMS? Carter et al.
`4.62.080
`
`. 350.8%. I5
`61" 98'?
`land:
`4,6?1fil}?
`
`
`4,703.4?2 10f198'! Bluntentritt et al
`3708
`
`I1} 987 Gounli ct :Il.
`.
`35fl.-’9h.l()
`4.208.425
`
`
`3513.00.18
`21988 Yamashila et a .
`4320.645
`
`4,740.95:
`4:19:38 Lizel el al.
`
`(List continued on next page.)
`
`
`
`OTHER PUBMCATIONS
`
`G. R. llarrison, Ph.l)., Sci). cl al.. Practical Spectroscopy,
`Chapter 4—Difiracli0n—Graling Spectrograph, Prentice—
`[lall (1984) [no month avaiiable).
`W.
`.l. Tomlinson, Wavelength multiplexing in mullimode
`optical fibers, Applied Optics, vol. 16, No. 8 (Aug. 192?).
`W. J. ‘l'nntlirtson et al_, Optical multiplexer [or multimnde
`liber transmission systems, Appl. Phys. [.etL. vol. 31, No. 3
`(Aug. 19W).
`W. .l. Tomlinsttn et al., Optical wavelength—division mulli—
`plexer for the I—1.4I.trm spectral region, Electronics Letters,
`vol. 14. N0. 11 (May 25. 1933).
`
`(List continued on next page.)
`
`Primmjt' Examiner—Rodney Bovcrnick
`Assistant Exmnt'ner—éiung T. Kim
`Attorney, Agent, or Hrnt—lenkens 8t. Gilchrist. PI:
`
`[57]
`
`ABSTRACT
`
`inte-
`A wavelength division multiplexer is provided thal
`grates an axial gradient refractive index element with a
`tiilIraclion grating to provide efficient coupling from a
`pluralit).r of inpul optical sources (each delivering a single
`wavelength to the device) which are multiplexed to a single
`polycliromalic beam for output to a single output optical
`receiver. The device comprises: (a) means for accepting
`optical
`input from at
`least one optical source. the means
`including a planar surface; [13) a coupler clement comprising
`(i)an axial gradient refractive index coll irnating lens having
`a planar entrance surface onto which the optical
`input
`is
`incident and (2) a homogeneous index hoot lens aflixcd to
`the axial gradient refractive index collimating lens and
`having a planar hut
`tilted exit surface; (e) a difliractien
`graling, such as a Littrow tlilfraction grating, on the tilted
`surface (il'lhc homogeneous index hoot lens which combines
`a plurality of spatially separated wavelengths from the
`optical
`light; and (d) means to output at
`least one
`multiplexed, polyeliromatie output beam, the means includ-
`ing a planar surface. The device may he operated in the
`forward direction as a multiplexcror in the reverse direction
`as a dcrnultiplexer.
`
`32 Claims, 8 Drawing Sheets
`
`
`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1021, Page 1
`Exhibit 1021, Page 1
`
`

`

`6,01 1,884
`Page 2
`
`US. PM'ENT DOCUMENTS
`
`
`
`
`350796.19
`571988 Nicia er al.
`4,741,588
`. 350796.19
`571988 Mahlein
`4,744,618
`
`. 350796.13
`571988 Nicia
`4,746,186
`
`571988 Danrmann el al.
`37073
`4,748,614
`
`. 350796.16
`671988 huge
`4,749.24?
`. 350796.12
`671988 Vollnrer .
`4,752,103
`
`771988 Mahlein
`35073
`4,760,569
`871988 Khoe el al.
`350796.19
`4,763,969
`
`l-[unsperger el al
`97198-8
`371173
`4,773,063
`
`1171988 Gidon et al.
`..
`350796.19
`4,786,133
`
`471989 Laude
`37073
`4,819,224
`
`. 350796.19
`571989 Lee
`4,834.485
`
`. 350796.19
`671989 laudc
`4,836,634
`371989 Kinney cl al.
`2507226
`4,857,726
`
`571990 llenry et al.
`..
`350796.19
`4.923.271
`571990 .Tannson at al.
`37073
`4,926,412
`671990 Clark et al.
`350796.19
`4,930,855
`671990 Kapnny e1 ai.
`350796.18
`4.934.784
`
`Jannsorr e: al.
`671991
`35073.7
`5,026,131
`471992 Ohtrchida ..
`3597124
`5,107,359
`
`.. 385749
`671992 McMahon .
`3,119.454
`
`1271992 Ohsllinra
`335743
`5,170,451
`
`
`771993 Chen cl :11.
`5.228.103
`171994 .Tannson ct :11.
`5,278,687
`
`1071994 Lang et at.
`5,355,237
`5,363,220 1171994 Kuwayama et al
`
`5,371,813
`1271994 Arligue
`3597127
`5,440,4l6
`371995 Collette! a].
`.
`3597110
`5,442,472
`871995 Skrohko
`
`971995 Boord et al.
`. 385737
`5,450,510
`
`3597569
`5,457,573
`1071.995
`Iida ct 3|.
`
`371996 Boudreau elal.
`5,510,910
`385724
`
`471996 Hosolrawa elul.
`5,513,289
`385733
`
`.......
`5,526,155
`671996 K110}: ct al.
`597131!
`
`3597653
`771996 Blankenhecier
`5,541,774
`
`. 385793
`5,555,334
`971996 {)hnishi cl al.
`1271996 Scnlscy ..........
`3597127
`5,583,683
`
`271997 I’eldman et al.
`5,606,434
`35973
`
`.. 385724
`...............
`5.657.406
`871997 Ball
`5.703.722 1.271997 Blankenbecler
`3597653
`
`
`5,742,415
`471993 Mimhi
`3597134
`
`5,745,270
`471993 Koch .....
`3597124
`35971.3(!
`5,745,271
`471998 Ford (:1 al.
`
`. 385724
`5,745,612
`471998 Wang et al.
`..
`3597130
`5,748,350
`571.998 Pan ct al.
`
`. 385737
`5,748,815
`571998 Hamel ct al
`
`671998 Bhagavatula ..
`.. 385724
`5,768.450
`771998 'lbm|inson,l[1 ..
`3597130
`5,777,763
`
`1171998 Jayaraman et al.
`. 372750
`5,835,517
`
`OTHER PU BLICM'lONS
`
`'1'. Miki et a1. Viabilities of the wavelength—division—mul-
`tiplexing transmission system over an optical fiber cable,
`IEEE Transactions on Communications. vol. Com—26. No. 7
`(Jul. 1971:).
`
`K. Aoyama et a1., Optical demulliplexer for a wavelenglh
`division multiplexing system. Applied Optics. vol. 18, No. 8
`(Apr. 15, 1979).
`
`K. Aoyama el al., Low—loss optical demulliplexer for WOM
`systems in the 08—pin wavelength region, Applied Optics,
`vol. 18, No. 16 (Aug. 15, 1979).
`
`R. Walanahe et 111., Optical IJemultiplexer Using Concave
`Grating in 0.7—0.9 um Wavelenglh Region. Electronics
`Letters, vol. 16. No. 3 (Jan. 31, 1980).
`
`K. Kobayashi cl al., Microopitc Grating Multiplexers and
`Optical [solalors for Fiber—Optic Communications, Journal
`of Quantum Electronics, vol. 013—16. No.
`I (Jan. I980).
`Yohi Fujii el al., Optical Demultiplexer Using a Silison
`Echelelte Grating. Journal of Quantum Electronics, vol.
`013—16, No. 2 (Feb. 1980).
`W]. 'lbrnlinson. Applications of GRIN—rod lenses in optical
`fiber communication systems. Applied Optics, vol. 19, No.
`'7 (Apr. 1. 1980).
`A. Nicia, Wavelenglh Multiplexing and Demultiploxing
`Systems for Singlemode and Multimode l-‘ibers, Conference
`Proceedings, European Conference on Optical Communica-
`tion (Sep. 8—1 I, I981).
`‘B. D. Metcall' et al., High—capacity wavelength demulti-
`plexer will: a Iarge—diarnler GRIN rod lens, Applied Optics,
`vol. 21. N0. 5 (Mar. I. 1982).
`.l. Lipson el al., low—Leos Wavelength Division Multiplex-
`ing (WDM) Devices for Single-Mode Systems, Journal of
`Lightwave Technology, vol. LT—l, No. 2 (Jun. 1983).
`G. Winner. Wavelenglh Multiplexing Components—A
`Review of Single—Mode Devices and their Applications,
`Journal of Lightwave Technology, vol. LT—2. No. 4 (Aug.
`1984}.
`H. Ishio et £11., Review and Status of Wavelength—Division-
`—Mulliplexing 'i‘echnology and [Ls Application. Journal of
`Lighlwave Technology, vol.
`[IT—2, No. 4 (Aug. [984).
`Y.
`I-‘ujii el al., Optical Demultiplexer Utilizing an Ebert
`Mounting Silicon Grating. Journal of Lightwave Technol-
`ogy, vol. 11-; No. 5 (Del. 1934).
`J. Lipson (:1 al., A Four—Channel Lightwave Subsystem
`Using Wavelength Division Multiplexing. IEEE Journal of
`[.ighlwave Technology. vol.
`[IT—3. No.
`] (Feb. 1935).
`ll. [lillerich et 3].. Wide Passband Grating Multiplexer for
`Mullimotle Fibers. Journal of Lightwave Technology, vol.
`LT—3, No. 3 (Jun. 1985).
`I. Lipson el al., ASix—‘Channcl Wavelength Mulliplcxcr and
`Demulliplexer [or Single Mode Systems, Journal of Light-
`wave 'l‘eclrnology, vol. [if—3, No. 5 (Oct. 1985).
`I. Nishi et al.. Broad Passhanrl MuItL’Demultiplexer for
`Mullimorle Fibers Using a Diffraction Grating and Relrore-
`fleetors, Journal of Lightwave Technology. vol. LT—S. N0.
`12 (Dec. 1987).
`ll. Moslehi et al., Fiber—optic wavelength—division mulli-
`plexing and demultiplexing using volume holographic grat-
`ings, Optic Letters, vol. 14, No. 19 (Oct. 1, 1989).
`Y. Huang et a1., Wavelenglh+divisionfimulliplexing and -—
`demultiplexing using substrate—mode grating pairs, Optics
`Letters, vol. 17, No. 22 (Nov. 15, 1992).
`M. We el al., Design Considerations for Rowland Circle
`Grating Used in Photonic Integrated Devices for WDM
`Applications, Journal ofljghlwave 'I‘echnology. vol. 12, No.
`11 (Nov. 1994}.
`A. Stavdas et all. Design of a holographic concave grating
`used as a multiplexer7den1ultiplexcr in dense wavelength-
`rouled optical networks with subnanomcter channel spacing,
`Journal of Modern Optics, vol. 42. No. 9. pp. 1863—1874
`(Sep. 1995).
`(1 Elton cl 3]., Four Channel Multimocle Wavelength Divi-
`sion [)emultiplexer (WDM) System Based on Surface—nor-
`rnal Volume Holographic Gratings and Substrate-guided
`Waves, SPIE, vol. 3288 {no date available}.
`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1021, Page 2
`Exhibit 1021, Page 2
`
`

`

`6,01 1,884
`Page 3
`
`A. Stavdas et al., Free-Space Aberration—Corrected DilIrac-
`tion Grating [)emultiplexer for Application in Densely—S-
`paced,
`thnanometer Wavelength Routed Optical Net~
`works,
`IEEE Electronic Letters, vol. 31, No. 16, pp.
`1368-1370 (Aug. 1995).
`D. Wisely, High perlon'nance 32 channel HDWDM multi-
`plexer with lum channel spacing and (Hum bandwidth.
`SPlE. vol. 15?8, l-‘iher Networks for Telephony and (IA'l'V
`(1991) (no month available).
`A. Cohen et al., Active management of lOO—GI-[z~spaced
`WUM channels, Optical Fiber Communicalion Conference
`and the international Conference on Integrated Optics and
`Optical Fiber Communication, Technical Digesl, Conl'er—
`encc Edition (Feb. 24, 1999].
`I}. Keyworlh el al,, Low Loss, 'l'entperalure Stable Diffrac-
`tion Grating Wavelength (DE) Mulliplexcr, National Fiber
`Optic Engineers Conference, Technical Proceedings, vol. I
`(Sep. 13—17. 1998}.
`M. Seki et al,, 2(l—Channel Micro—Optic Grating [)emulti-
`plexer for |.l—l.oum Band Using a Small Focusing Param-
`eter Graded-Index Rod Lens, Eleclmnic letters, vol. 18,
`No. 6 (Mar. 18, 1932).
`A. Koonen. A Compact Wavelength Demulliplexer Using
`Both interference Filters and a IJiWraetion (lraling, Euro-
`pean Conference of Optical Communications, Conference
`Proceedings (Sep. 8-11, 1981].
`J. Conradi et al.. Laser Based WDM Multichannel Video
`‘l‘ransmission System, Electronic Letters, vol. 17. No. 2 (Jan.
`22. 1981).
`.l. Laude et al,, Wavelength division mulliplexingr'demulti-
`plexing (WDM) using dilfraclion gratings, SPIE, vol. 503,
`Application, Theory, and I-‘abricalionol' Periodic Stmctures
`(1984) (No month available).
`A. Livanos et al,, Chirped—graling demulitplexer in dielec-
`tric waveguides. Applied Physics Letlers, vol. 31], No.
`lU
`(May 1977).
`ll. Obara et aI.. Star Coupler Based WDM Switch Employ-
`ing Tunable Devices With Reduced 'l‘unability Range, Elec-
`tronic Letters, vol. 28. No. l3 (Jun. [992).
`A. Willner el al., 2—D WDM Oplical lnlcrconnections Using
`Mulliple~Wavelcngll1 VCSEL's
`for Simullaneous
`and
`Reconfigurable Communication Among Many Planes, [IEEE
`Phoyonics 'E‘echnology Letters, vol. 5, No. T (Jul. 1993).
`
`M. Wang el al., Five Channel Polymer Waveguide Wave-
`lenglh Division IJeniultiplexer for the New Infrared. [L’L‘E
`Photonics 'l'echnology letters, vol. 3, No.
`I (Jan. 1991).
`M. Li et al..
`‘I‘wo—channel surface—normal wavelength
`demultiplexer using substrate guided waves in conjunction
`with multiplexed waveguide holograms, Appl. Phys. Lelt.,
`vol. 66, No. 3 (Jan. 1995}.
`.l. Laude et al., Slimax, A Grating Multiplexer for Mono-
`mode or Multimode l-‘ibeis, Ninth European Conference on
`Optical Communicaton—ECOCSHI, Geneva, Switzerland
`(Oct. 23—26, 1983).
`W]. Tomlinson, “Wavelength multiplexing in mullimodc
`oplical
`fibers", Applied Optics, vol.
`16, No. 8, pp.
`2180-2194 (Aug. 19'”).
`AC. Livanos et al, "Chirped-grating demultiplexers in
`dielectric waveguides", Applied Physics letters, vol. 31],
`No, II]. pp. 519—52l (May 15, 197(7).
`Ilideki lshio et al, "Review and status of wavelength—divi-
`sion multiplexing technology and its application", Journal of
`Lighlwave Technology, vol. LT-Z, No. 4, pp. 448-463 (Aug.
`1984).
`H. Ohara et al, "Star coupler based WDM switch employing
`tunable devices with reduced tunability range". Electronic
`|..etlers, vol. 28, No. 13, pp. 268—270 (Jun. IS, 1993).
`A.L-'. Willner et al, "3—D WDM optical
`interconnections
`using mulliple—wavelenglh VC'SEL's for simultaneous and
`reconfigurable communicalion among many planes", IEEE
`Photonics 'l‘echnology Letters. vol. 5. No. 7’. pp. 838—841
`(Jul. 1993).
`Yang—’l'ang Huang et al, "Wavelength—division—multiplcx-
`ing and demeltiplexing by using a suletratL‘umode grating
`pair", Optics letters, vol. 1?, No. 22, pp. lfiZQ—lfifil (Nov.
`15, l992).
`MR. Wang et al, "i-‘ive—channel polymer waveguide divi-
`sion demultilexcr for [be near infrared", IEEE Photonics
`Technology Letters, vol. 3, No. I, pp. 36—38 (Jan. 199]).
`Maggie M. Li el al, "Two—channel surface—normal wave—
`lenglh division demultiplcxer using subslrale guided waves
`in conjunction with multiplexed waveguide holograms",
`Appl. Phys. 1.elt.vol. 66, No. 3. pp. 262—264(Jan. 11'), 1995).
`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1021, Page 3
`Exhibit 1021, Page 3
`
`

`

`US. Patent
`
`Jan. 4, 2000
`
`Sheet 1 of 8
`
`6,011,884
`
` <_‘.O_n_
`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1021, Page 4
`Exhi
`it 1021, Page 4
`
`

`

`US. Patent
`
`Jan. 4, 2000
`
`Sheet 2 0f 8
`
`6,011,884
`
`FIG.2C
`
`PM]
`(3 0000100”
`
`
`
`”—FIG.ZB
`
`OW
`
`34
`
`FIG.2A
`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1021, Page 5
`Exhibit 1021, Page 5
`
`

`

`US. Patent
`
`Jan. 4, 2000
`
`Sheet 3 of 8
`
`6,011,884
`
`
`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1021, Page 6
`Exhi
`it 1021, Page 6
`
`

`

`US. Patent
`
`Jan. 4, 2000
`
`Sheet 4 0f 8
`
`6,011,884
`
`FIG.4
`
`
`
`
`
`
`
`www-
`
`g—A43‘s.—
`
`
`
`
`\:x ._
`
`
`
`
`\_\k\\.
`
`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1021, Page 7
`Exhibit 1021, Page 7
`
`

`

`US. Patent
`
`Jan. 4, 2000
`
`Sheet 5 0f 8
`
`6,011,884
`
`E
`:-
`
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`:-
`
`Ausuew;
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`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1021, Page 8
`Exhibit 1021, Page 8
`
`

`

`US. Patent
`
`Jan. 4, 2000
`
`Sheet 6 0f 8
`
`6,011,884
`
`FIG.6
`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1021, Page 9
`Exhibit 1021, Page 9
`
`

`

`US. Patent
`
`Jan. 4, 2000
`
`Sheet 7 0f 8
`
`6,011,884
`
`FIG?
`
`24
`
`\‘\m\\\\
`
`
` 30
`
`
`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1021, Page 10
`Exhibit 1021, Page 10
`
`

`

`US. Patent
`
`Jan. 4, 2000
`
`Sheet 0 0f 8
`
`6,011,884
`
`10b
`
`W
`
`D1—
`‘—
`
`FIG.8
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`
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`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1021, Page 11
`Exhibit 1021, Page 11
`
`

`

`6,011,884
`
`1
`INTEGRATED BI-DIRECTIONAI. AXIAL
`GRADIENT REFRACTIVE INDEX;Ir
`DIFFRACTII)N GRATING WAVELENGTH
`DIVISION MULTIPLEXER
`
`CROSS-REFERENCE TO RELATED
`APPLICATIONS
`
`The present application is related to two other patent
`applications,
`the first entitled "Integrated iii-Directional
`IJual Axial Gradient Refractive [ndefoilTraetion Grating
`Wavelength Division Multiplexer,” Ser. No. (“990,199, and
`the second entitled “integrated BiDirectional Gradient
`Refractive Index Wavelength Division Multiplexer" Ser. No.
`[I8t’990_198, both filed on even date herewith and assigned to
`the same assignee. This and the two related applications are
`all directed to wavelength division multiplexers, and ditfer
`in the presence or absence of a dilIraction grating and the
`number 01’ gradient refractive index elements.
`
`Ill
`
`15
`
`'I‘ECI [NICAL HELD
`
`The present invention relates generally to axial gradient
`refractive index lettses, and, more particularly,
`to axial
`gradient refractive index lenses employed in wavelength
`division multiplexing applications.
`BACKGROUND ART
`
`Wavelength division multiplexing (WDM) is a rapidly
`emerging technology that enables a very significant increase
`in the aggregate volume ofdata that can be transmitted over
`optical fibers. Traditionally, most optical fibers have been
`used to unidirectionally carry only a single data channel at
`one wavelength. The basic concept of WDM is to launch and
`retrieve multiple data channels in and out. respectively, from
`an optical fiber. Each data channel is transmitted at a unique
`wavelength, and the wavelengths are appropriately selected
`such that the channels do not interfere with each other. and
`the optical transmission losses of the iiber are low. 'l‘oday.
`commercial WDM systems exist that allow transmission of
`2 to 32 simultaneous channels.
`
`WUM is a cost—efiectivc method of increasing the volume
`of data (commonly termed bandwidth) transferred over
`optical fibers. Alternate competing technologies to increas-
`ing bandwidth include the burying of additional fiber optic
`cable or increasing the transmission speed on optical fiber.
`The burying of additional Iiber optic cable costs on the order
`of $15,000 to $40,000 per Km.
`Increasing the optical
`transmission rate is increasing limited by speed and
`economy of the electronics surrounding the fiber optic
`system. One of the primary strategies to electronically
`increasing bandwidth has been to use time division multi-
`plexing (YUM), which gangs or multiplexes multiple lower
`rate electronic data channels together into a single very high
`rate channel. This technology has for the past 20 years been
`very eiIective [or increasing bandwidth; however, it is now
`increasingly difficult to improve transmission speeds, both
`from a
`technological and economical standpoint. WDM
`offers the potential ofholh an economical and technological
`solution to increasing bandwidth by using many parallel
`channels. WDM is complimentary to TDM. that is, WDM
`can allow many simultaneous high transmission rate TDM
`channels to he passed over a single optical fiber.
`The use of WDM to increase bandwidth requires two
`basic devices that are conceptually symmetrical. The first
`device is a wavelength division multiplexer. This device
`takes multiple beams—each with discrete wavelengths and
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`initially spatially separated in space—and provides a means
`ofspatially combining all of' the different wavelength beams
`into a single polychromatic beam suitable for launching into
`an optical
`fiber. The multiplexer may he a completely
`passive optical device or may indude electronics that control
`or monitor the performance of the multiplexer. The input of
`the multiplexeris typically accomplished with optical fibers;
`however,
`laser diodes or other optical sources may be
`employed. The output of the multiplexer is typically an
`optical fiber.
`Similarly, the second device for WDM is a wavelength
`division demultiplexer. This device is functionally the oppo-
`site 01‘ the multiplexer; it receives a polychromatic beam
`input from an optical fiber and provides a means of spatially
`separating the wavelengths. The output of the demuitiplcxcr
`is typically interfaced to optical fibers or to photodetcctors.
`During the past 20 years, various types of WDMs have
`been proposed and demonstrated; sec, e.g., (l) W. J.
`Tomlinson, Appir'ed Optics, Vol. 16, No. 8, pp. 2180—2194
`(August 19??); (2) A. C. Livanos et al, Applied Physics
`t.crtet‘s,Vol. 3(t,No. ltt, pp. 519—521 (May 15, 1977); (3) ll.
`Ishio et al, Journal ofLigitrwow Tecitnoiogv, W11. 2, No. 4,
`pp. 443—463 (August 1984); (4) H. Obara ct ai, Hicctmrtics
`Letters, Vol. 28, No. 13, pp. 1263—1270 (Jun. 18, 1992); (5]
`A. E. Wiliner et al,flii~.'i'-.‘ i’t‘torortics Technology Letters. Vol.
`5, No. ‘3', pp. 838—841 (July t95‘3); and (6)Y. 1'. Huang et al.
`Optics Letters, Vol. 1?, No. 22, pp. 1629—1631 (Nov. 15,
`1.992}.
`However, despite all of the above approaches, designs,
`and technologies,
`there remains a real need for a WDM
`devices which possesses all the characteristics of: low cost,
`component integration, environment and thermal stability.
`low channel crosstalk,
`low channel signal
`loss, ease of
`interfacing, large number at channels, and narrow channel
`spacing.
`
`DISCLOSURE 01“ INVENTION
`
`In accordance with the present invention, a wavelength
`division multiplexer or demultiplexer combines an axial
`gradient refractive index element with a diffraction grating
`to provide an integrated, bidirectional wavelength division
`multiplexer or demultiplexer device. For simplicity,
`the
`multiplexer function will be extensively discussed; however,
`such discussions of the invention will also be directly
`applicable to the demultiplexcr due to the symmetry of the
`multiplexer and demultiplexer function. The multiplexer
`device of the present invention comprises:
`input
`(a) a means for accepting a plurality of optical
`beams containing at least one wavelength from optical
`libers or other optical sources such as lasers or laser
`diodes, the means including a planar front surface onto
`which the optical input light is incident and suitable for
`the connection of input opt icai fibers or integration of
`other devices;
`(h) a coupler subsystem comprising (1) an axial gradient
`refractive index collimating lens operative associated
`with the planar front surface and (2) a homogeneous
`index boot lens affixed to the axial gradient refractive
`index collimating lens and having a planar but titted
`back surface;
`(c) a near—Littmw diffraction grating operatively associ—
`ated with the homogeneous index boot lens. formed or
`aflixed at the planar exit surface of the coupler sub-
`system which combines a plurality of spatially sepa-
`rated wavelengths into at least a single poiychromatie
`optical
`light beam and reflects the combined optical
`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1021, Page 12
`Exhibit 1021, Page 12
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`6,011,884
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`3
`beam back into the coupler subsystem at essentially the
`same angle as the incident beams;
`(d) an optional array of electmoptieal elemean for refract—
`ing the plurality of wavelengths to provide channel
`routing or switching capabilities; and
`(c) a means of outputting at least one multiplexed, poly-
`chromatic output beam for at
`least one optical fiber,
`said means being located at the same input sur face in
`(a).
`'lhe device of the present invention may be operated in
`either the forward direction to provide a multiplexer func-
`tion or in the reverse direction to provide a demultiplexer
`function.
`Further. the device of the present invention is inherently
`fully bi-directional and can be used simultaneously as a
`multiplexer and dernulliplexer for applications such as net—
`work hubs or intersections that distribute channels to various
`areas of a network. The axial gradient refractive index and
`dilfraction grating-based WUM devices of the present
`invention are unique because they contain one or more
`homogeneous index hoot lenses which allows integration of
`all the optical components into a single integrated device.
`This greatly increases the ruggedness, environmental and
`thermal stability while simultaneously avoiding the intro-
`duction of air spaces which cause increased alignment
`sensitivity, device packaging complexity, and cost.
`Additionally, the homogeneous index boot lenses provide
`large. planar surfaces for device assembly, alignment and the
`integration of additional device functions. The use of an
`axial gradient refractive index lens allows very high perfor-
`mance imaging from a lens with traditional spherical
`surfaces, thereby providing the diEt'raction-iimited optical
`imaging necessary for WDM applications. Further, axial
`gradient refractive index lenses are formed with high quality
`and low cost. Alternately, aspheric shaped lenses could be
`used in place of axial gradient refractive index lenses;
`however, the collimatirtg performance is the same, but it is
`exceedingly diflicull to create a one-piece, integrated device
`with aspheric surfaces. Further, aspherical lenses are typi-
`cally very costly and suffer from ghosting—types of reflec‘
`tions which are very undesirable.
`'Ilte integration of the WIJM device allows for a compact,
`robust, and environmentally and thermally stable system. In
`particular, inlegrat ion of the components into a solid block
`maintains component alignment. which provides long-term
`performance in contrast to non-integrated air-spaced devices
`that characteristically degrade in alignment and therefore
`performance over time.
`Overall, the present invention features a novel approach
`to WDM. The use of optical lenses in conjunction with a
`diffraction grating allows all wavelengths to be multiplexed
`simultaneously and treated uniformly. This is contrast to the
`less desirable serial WUM approaches that use interference
`filter-based or
`fiber Bragg gratings. Such serial WDM
`approaches sutIer from significant optical
`loss, crosstalk,
`alignment. and temperature issues. Further, compared to
`other parallel multiplexing approaches such as array
`waveguide grating devices, fused fiber couplers, or tree
`waveguide couplers,
`the present
`invention performs the
`wavelength separation freely inside glass as opposed to
`inside of lossy waveguiding structures. Thus,
`the present
`invention has the distinct advantages of lower optical signal
`loss through the device and ease of assembly and alignment
`compared to the current art.
`Other objects, features, and advantages of the present
`invention will become apparent upon consideration of the
`following detailed descriptions and accompanying
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`drawings, in which like reference designations represent like
`features throughout the FIGURES. It will be apparent to one
`skilled in the art that additional objects, features, and advan—
`tages not expressly discussed here are inherent to and follow
`from the spirit of this invention.
`BRIEF DESCRIPTION 0|“ THE DRAWINGS
`
`The drawings referred to in this description should be
`understood as not being drawn to scale except if specifically
`noted.
`
`FIG. I is a side elevational schematic view (l-‘IG. In) and
`a top plan schematic View (FIG.
`lb) of a wavelength
`division multiplexer device of the present invention, with an
`axial gradient refractive index lens, near-Littrow diffraction
`grating. and multiple optical fiber inputs multiplexed to one
`optical fiber output;
`FIG, 2a is a perspective view of a portion of the device of
`FIG. 1.
`illustrating in detail the input and output optical
`connections to the device;
`FIG. 2!: is a perspective view of the input portion of the
`device off-1G. 1. illustrating an alternate input configuration
`in which the input is an array of laser diodes;
`FIG. 2C is a perspective view ol'a portion of the device of
`FIG. 1. illustrating an altemate output configuration for a
`demultiplexer device in which the output
`is an array of
`photodetectors;
`FIG. .3 is a side eIevalional schematic view (FIG. 3a) and
`a top plan schematic view (FIG. 3b) similar to the device of
`FIG. 1, but omitting a homogeneous index boot lens element
`between the input and the axial gradient refractive index
`collimating lens;
`FIG. 4 is a perspective view of a portion of the device of
`FIG. 1, but including an array ofelectrooptical heamsteering
`elements (parallel to the grating direction) to individually
`beamsteer each input channel to an output fiber port;
`FIGS. Sa—Sc are plots on coordinates of intensity and
`wavelength, depicting different intensity profiles for diflcr—
`ent configurations of the multiplexer of the present inven-
`tton;
`FIG. 6 is a perspective view of a portion of the device of
`FIG. 1, similar to that of FIG. 2a. but including an array of
`electrooptical beamsteering elements (perpendicular to the
`grating direction) to individually beamstcer each input chan—
`nel to an output fiber port;
`FIG. 7 is a perspective view of a portion of the device of
`FIG. 1. similar to that of FIG. 2a, but including an elec~
`trooptica] beamsleeril'lg element to individually hearnsteer
`each input channel to an output fiber port; and
`FIG, 8 is a perspective view of a portion of the device of
`FIG. I, but employing two multiplexers to perform a chan~
`nel blocking function by incorporating an electrooptical
`blocking array on the input [ace of one multiplexer.
`BES'!‘ MODES FOR CARRYING ()U'I'TIIE
`INVEN‘I'IUN
`
`Reference is now made in detail to specific embodiments
`of the present invention, which illustrate the best modes
`presently contemplated by the inventors for practicing the
`invention. Alternative embodiments are also brietly
`described as applicable.
`FIG.
`1 depicts two vieWs of a preferred embodiment of
`the present
`invention, which embodies an axial gradient
`refractive indexr'ditfraction grating wavelength division
`multiplexer device. Specifically, FIG. 1:.- illuslrales the side
`elevational view of the device, while FIG. lb illustrates the
`top plan view.
`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1021, Page 13
`Exhibit 1021, Page 13
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`6,011,884
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`5
`The device 10 of the first embodiment takes an input liber
`array 12 of N discrete wavelengths of light 14 and spatially
`combines then: into a single optical beam 16 and outputs the
`single beam to a single optical fiber output 18. Each wave—
`length is transmitting information superimposed on it by
`other means, which are not shown here and which do not
`form a part of this invention, but are well known in this art.
`'lhe device It) further comprises a coupler element 20; on
`the exit surface 20b of the coupler element
`is formed or
`placed a ncar—littrovt:I difl‘raction grating 22. The near—
`Littrow dilIraction grating 22 provides both the function of
`angularly dispersing optical beams of (lificring wavelength
`and reflecting the optical beamsback at very nearly the same
`angle as the incident angle.
`In the present invention. the diffraction grating 22 is used
`to provide angular dispersion, the amount ofwhich depends
`upon the wavelength ofeach incident optical beam. l-‘urther.
`the diffraction grating 22 is oriented at a special angle
`relative to the optical axis of the device 10 in order to obtain
`the [.ittrow diffraction condition for one wavelength that lies
`within or near the wavelength range for the plurality of
`optical beams present. The Littrow diffraction condition
`requires that a light beam be incident on and reflector] back
`from the grating at the same exact angle. Therefore, it will
`be readily apparent to one skilled in the art that a near—
`Littrow dilTraction grating is used to obtain near—[.jttrow
`diffraction for each of the plurality of wavelengths present.
`The Littrow difi‘raction angle is determined by the well‘
`known formula
`
`rrrh-thfsin 0,]
`
`where ITI is the diffraction order, ?. is the wavelength, d is the
`diffraction grating groove spacing, and 0.,-
`is
`the same
`incident and diffracted angle. lt will be readily apparent to
`one skilled in the art
`that
`the diffraction grating angle
`depends upon numerous variables, which may be varied as
`necessary to optimize the performance of the device. For
`example, variables affecting the grating diffraction angle
`include the desired grating diffraction order, grating blaze
`angle, number of channels, spatial separation of channels,
`and wavelength range of the device.
`The coupler element 2|] comprises a first homogeneous
`index boot
`lens 24 joined or affixed to an axial gradient
`refractive index collimating lens 26. The axial gradient
`refractive index lens in turn isjoined or affixed to a second
`homogeneous index boot lens 28. The joining or aflixing is
`accomplished using optical cement or other optically trans-
`parent hondingtechnique. In this. first embodiment, the array
`12 of optical fibers 12' are positioned so that tight emanating
`from the end the optical fibers is incident on the entrance
`surface 20a of the coupler element 20. Each fiber 12'
`provides light beams of discrete wavelengths.
`FIG. 2a depicts the details of coupling the input fiber
`array 12 into the coupler 2t} and launching a plurality of
`optical beams 14 therein. one for each ftber 12', using a
`suitable couplerr'intcrconncct 30. Similarly, the combined
`optical beam 16 is coupl