United States Patent
`Dueck et al.
`
`[19]
`
`[54]
`
`[75]
`
`INTEGRATED BI-DIRECTIONAL AXIAL
`GRADIENT REFRACTIVE
`INDEX/DIFFRACTION GRATING
`WAVELENGTH DIVISION MULTIPLEXER
`
`Inventors: Robert H. Dueck, Santa Ana, Calif;
`Robert K. Wade, EdgeWood, N.Mex.;
`Boyd V. Hunter; Joseph R.
`Dempewolf, both of Albuquerque,
`N.Mex.
`
`Assignee: LightChip, Inc., Salem, NH.
`
`Appl. No.: 08/990,197
`Filed:
`Dec. 13, 1997
`
`Int. Cl.7 ..................................................... .. G02B 6/28
`U.S. Cl. ............................... .. 385/24; 385/33; 385/34;
`385/37; 385/14; 385/49; 385/39; 359/130;
`359/131; 372/50
`Field of Search ................................ .. 385/24, 33, 34,
`385/37, 14, 49, 39; 359/130, 131; 372/50
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`4,111,524
`
`9/1978 Tomlinson, III ................... .. 350/9619
`
`4,153,330
`
`5/1979 Tomlinson, III . . . . .
`
`. . . .. 350/9617
`
`4,198,117
`
`4/1980 Kobayashi . . . . . . .
`
`. . . .. 350/9619
`
`4,274,706
`
`6/1981 Tangonan . . . . .
`
`. . . .. 350/9619
`
`. 350/9619
`7/1981 Colombini ..... ..
`4,279,464
`356/328
`4,299,488 11/1981 Tomlinson, III .
`. 350/9619
`4,343,532
`8/1982 Palmer ............... ..
`350/9619
`4,387,955
`6/1983 Ludman et a1. .
`350/9618
`4,479,697 10/1984 Kapany et a1. ..
`4,522,462
`6/1985 Large et a1. ....................... .. 350/9619
`4,583,820
`4/1986 Flamand et a1. ................... .. 350/9619
`
`4,622,662 11/1986 Laude et al. . . . . . . . . .
`
`. . . . . .. 370/3
`
`4,626,069 12/1986 Dammann et al. ..
`
`350/162.2
`
`4,634,215
`
`1/1987 Reule . . . . . . . . . . . . . . . . . . .
`
`. . . .. 350/9616
`
`350/9619
`2/1987 Bussard et al. ..
`4,643,519
`350/9619
`3/1987 Carter et a1.
`4,652,080
`. 350/9615
`6/1987 Laude ................. ..
`4,671,607
`..... .. 370/3
`4,703,472 10/1987 Blumentritt et al.
`350/9616
`4,708,425 11/1987 Gouali et al. .......... ..
`350/9618
`4,726,645
`2/1988 Yamashita et al.
`4,740,951
`4/1988 Lizet et a1. ................................ .. 370/3
`(List continued on next page.)
`
`US006011884A
`Patent Number:
`Date of Patent:
`
`[11]
`[45]
`
`6,011,884
`Jan. 4, 2000
`
`OTHER PUBLICATIONS
`
`G. R. Harrison, Ph.D., Sc.D. et al., Practical Spectroscopy,
`Chapter 4—Diffraction—Grating Spectrographs, Prentice—
`Hall (1984) (no month available).
`W. J. Tomlinson, Wavelength multiplexing in multimode
`optical ?bers, Applied Optics, vol. 16, No. 8 (Aug. 1977).
`W. J. Tomlinson et al., Optical multiplexer for multimode
`?ber transmission systems, Appl. Phys. Lett., vol. 31, No. 3
`(Aug. 1977).
`W. J. Tomlinson et al., Optical Wavelength—division multi
`plexer for the 1—1.4 pm spectral region, Electronics Letters,
`vol. 14, No. 11 (May 25, 1973).
`
`(List continued on next page.)
`
`Primary Examiner—Rodney Bovernick
`Assistant Examiner—Sung T. Kim
`Attorney, Agent, or Firm—Jenkens & Gilchrist, PC.
`
`[57]
`
`ABSTRACT
`
`A Wavelength division multiplexer is provided that inte
`grates an axial gradient refractive index element With a
`diffraction grating to provide ef?cient coupling from a
`plurality of input optical sources (each delivering a single
`Wavelength to the device) Which are multiplexed to a single
`polychromatic 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; (b) a coupler element comprising
`(1) an axial gradient refractive index collimating lens having
`a planar entrance surface onto Which the optical input is
`incident and (2) a homogeneous index boot lens af?xed to
`the axial gradient refractive index collimating lens and
`having a planar but tilted exit surface; (c) a diffraction
`grating, such as a LittroW diffraction grating, on the tilted
`surface of the homogeneous index boot lens Which combines
`a plurality of spatially separated Wavelengths from the
`optical light; and (d) means to output at least one
`multiplexed, polychromatic output beam, the means includ
`ing a planar surface. The device may be operated in the
`forward direction as a multiplexer or in the reverse direction
`as a demultiplexer.
`
`32 Claims, 8 Drawing Sheets
`
`10
`
`Petitioner Ciena Corp. et al.
`Exhibit 1021-1
`
`

`

`6,011,884
`Page 2
`
`US. PATENT DOCUMENTS
`
`5/1988 Nicia et al. ........................ .. 350/96.19
`4,741,588
`5/1988 Mahlein
`350/96.19
`4,744,618
`5/1988 Nicia ............... ..
`. 350/96.13
`4,746,186
`5/1988 Dammann et al.
`..... .. 370/3
`4,748,614
`6/1988 Large ................................. .. 350/96.16
`4,749,247
`6/1988 Vollmer .............................. .. 350/96.12
`4,752,108
`7/1988 Mahlein
`...... .. 350/3
`4,760,569
`8/1988 Khoe et al. ..... ..
`350/96.19
`4,763,969
`9/1988 Hunsperger et al. ..................... .. 370/3
`4,773,063
`4,786,133 11/1988 Gidon et al. ....................... .. 350/96.19
`
`4,819,224
`
`4/1989 Laude . . . . . . . .
`
`. . . . . . .. 370/3
`
`4,834,485
`4,836,634
`4,857,726
`4,923,271
`4,926,412
`4,930,855
`4,934,784
`5,026,131
`5,107,359
`5,119,454
`
`. 350/96.19
`5/1989 Lee
`350/96.19
`6/1989 Laude .......... ..
`250/226
`8/1989 Kinney et al.
`350/96.19
`5/1990 Henry et al. .... ..
`5/1990 Jannson et al. ........................... .. 370/3
`6/1990 Clark et al. ........................ .. 350/96.19
`6/1990 Kapany et al.
`350/96.18
`6/1991 Jannson et al.
`350/3.7
`4/1992 Ohuchida .............................. .. 359/124
`6/1992 McMahon ............................... .. 385/49
`
`5,170,451 12/1992 Ohshima . . . . . . .
`
`7/1993 Chen etal.
`5,228,103
`1/1994 Jannson et al.
`5,278,687
`5,355,237 10/1994 Lang et al. ...... ..
`5,363,220 11/1994 Kuwayama et al.
`
`. . . . .. 385/43
`
`385/14
`359/125
`359/130
`..... .. 359/3
`
`5,371,813 12/1994 Artigue . . . . . . . . . . . . .
`
`. . . . .. 385/24
`
`359/127
`8/1995 Cohen et al. .
`5,440,416
`359/110
`8/1995 Skrobko ...... ..
`5,442,472
`385/37
`9/1995 Boord et al. ..
`5,450,510
`359/569
`5,457,573 10/1995 Iida et al. ........ ..
`385/24
`5,500,910
`3/1996 Boudreau et al.
`385/33
`5,513,289
`4/1996 Hosokawa et al.
`359/130
`5,526,155
`6/1996 Knox et al. ..... ..
`359/653
`5,541,774
`7/1996 Blankenbecler ..
`385/93
`5,555,334
`9/1996 Ohnishi et al.
`5,583,683 12/1996 Scobey .................................. .. 359/127
`5,606,434
`2/1997 Feldman et al. .......................... .. 359/3
`
`5,657,406
`
`8/1997 Ball . . . . . . . . . . . . . . . . . . .
`
`. . . . .. 385/24
`
`359/653
`5,703,722 12/1997 Blankenbecler
`359/134
`5,742,416
`4/1998 MiZrahi ....... ..
`5,745,270
`4/1998 Koch ..................................... .. 359/124
`5,745,271
`4/1998 Ford et al. ............................ .. 359/130
`5,745,612
`4/1998 Wang et al. ..
`385/24
`5,748,350
`5/1998 Pan et al. .... ..
`359/130
`5,748,815
`5/1998 Hamel et al. .
`385/37
`5,768,450
`6/1998 Bhagavatula ............................ .. 385/24
`5,777,763
`7/1998 Tomlinson, III ...................... .. 359/130
`5,835,517 11/1998 Jayaraman et al. ..................... .. 372/50
`
`OTHER PUBLICATIONS
`
`T. Miki et al., Viabilities of the Wavelength—division—mul
`tiplexing transmission system over an optical ?ber cable,
`IEEE Transactions on Communications, vol. Com—26, No. 7
`(Jul. 1978).
`K. Aoyama et al., Optical demultiplexer for a Wavelength
`division multiplexing system, Applied Optics, vol. 18, No. 8
`(Apr. 15, 1979).
`K. Aoyama et al., LoW—loss optical demultiplexer for WDM
`systems in the 0.8—pm Wavelength region, Applied Optics,
`vol. 18, No. 16 (Aug. 15, 1979).
`R. Watanabe et al., Optical Demultiplexer Using Concave
`Grating in 0.7—0.9 um Wavelength Region, Electronics
`Letters, vol. 16, No. 3 (Jan. 31, 1980).
`
`K. Kobayashi et al., Microopitc Grating Multiplexers and
`Optical Isolators for Fiber—Optic Communications, Journal
`of Quantum Electronics, vol. QE—16, No. 1 (Jan. 1980).
`Yohi Fujii et al., Optical Demultiplexer Using a Silison
`Echelette Grating, Journal of Quantum Electronics, vol.
`QE—16, No. 2 (Feb. 1980).
`W. J. Tomlinson, Applications of GRIN—rod lenses in optical
`?ber communication systems, Applied Optics, vol. 19, No.
`7 (Apr. 1, 1980).
`A. Nicia, Wavelength Multiplexing and Demultiplexing
`Systems for Singlemode and Multimode Fibers, Conference
`Proceedings, European Conference on Optical Communica
`tion (Sep. 8—11, 1981).
`B. D. Metcalf et al., High—capacity Wavelength demulti
`plexer With a large—diamter GRIN rod lens, Applied Optics,
`vol. 21, No. 5 (Mar. 1, 1982).
`J. Lipson et al., LoW—Loss Wavelength Division Multiplex
`ing (WDM) Devices for Single—Mode Systems, Journal of
`LightWave Technology, vol. LT—1, No. 2 (Jun. 1983).
`G. WinZer, Wavelength 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 al., RevieW and Status of Wavelength—Division
`—Multiplexing Technology and Its Application, Journal of
`LightWave Technology, vol. LT—2, No. 4 (Aug. 1984).
`Y. Fujii et al., Optical Demultiplexer Utilizing an Ebert
`Mounting Silicon Grating, Journal of LightWave Technol
`ogy, vol. LT—2, No. 5 (Oct. 1984).
`J. Lipson et al., A Four—Channel LightWave Subsystem
`Using Wavelength Division Multiplexing, IEEE Journal of
`LightWave Technology, vol. LT—3, No. 1 (Feb. 1985).
`B. Hillerich et al., Wide Passband Grating Multiplexer for
`Multimode Fibers, Journal of LightWave Technology, vol.
`LT—3, No. 3 (Jun. 1985).
`J. Lipson et al., ASix—Channel Wavelength Multiplexer and
`Demultiplexer for Single Mode Systems, Journal of Light
`Wave Technology, vol. LT—3, No. 5 (Oct. 1985).
`I. Nishi et al., Broad Passband Multi/Demultiplexer for
`Multimode Fibers Using a Diffraction Grating and Retrore
`?ectors, Journal of LightWave Technology, vol. LT—5, No.
`12 (Dec. 1987).
`B. Moslehi et al., Fiber—optic Wavelength—division multi
`plexing and demultiplexing using volume holographic grat
`ings, Optic Letters, vol. 14, No. 19 (Oct. 1, 1989).
`Y. Huang et al., Wavelength—division—multiplexing and —
`demultiplexing using substrate—mode grating pairs, Optics
`Letters, vol. 17, No. 22 (Nov. 15, 1992).
`M. Wu et al., Design Considerations for RoWland Circle
`Gratings Used in Photonic Integrated Devices for WDM
`Applications, Journal of LightWave Technology, vol. 12, No.
`11 (Nov. 1994).
`A. Stavdas et al., Design of a holographic concave grating
`used as a multiplexer/demultiplexer in dense Wavelength—
`routed optical networks With subnanometer channel spacing,
`Journal of Modern Optics, vol. 42, No. 9, pp. 1863—1874
`(Sep. 1995).
`C. Zhou et al., Four Channel Multimode Wavelength Divi
`sion Demultiplexer (WDM) System Based on Surface—nor
`mal Volume Holographic Gratings and Substrate—guided
`Waves, SPIE, vol. 3288 (no date available).
`
`Petitioner Ciena Corp. et al.
`Exhibit 1021-2
`
`

`

`6,011,884
`Page 3
`
`A. Stavdas et al., Free—Space Aberration—Corrected Diffrac
`tion Grating Demultiplexer for Application in Densely—S
`paced, Subnanometer Wavelength Routed Optical Net
`works, IEEE Electronic Letters, vol. 31, No. 16, pp.
`1368—1370 (Aug. 1995).
`D. Wisely, High performance 32 channel HDWDM multi
`plexer With 1nm channel spacing and 0.7nm bandwidth,
`SPIE, vol. 1578, Fiber Networks for Telephony and CATV
`(1991) (no month available).
`A. Cohen et al., Active management of 100—GHZ—spaced
`WDM channels, Optical Fiber Communication Conference
`and the International Conference on Integrated Optics and
`Optical Fiber Communication, Technical Digest, Confer
`ence Edition (Feb. 24, 1999).
`B. KeyWorth et al., LoW Loss, Temperature Stable Diffrac
`tion Grating Wavelength (DE) Multiplexer, National Fiber
`Optic Engineers Conference, Technical Proceedings, vol. I
`(Sep. 13—17, 1998).
`M. Seki et al., 20—Channel Micro—Optic Grating Demulti
`plexer for 1.1—1.6um Band Using a Small Focusing Param
`eter Graded—Index Rod Lens, Electronic Letters, vol. 18,
`No. 6 (Mar. 18, 1982).
`A. Koonen, A Compact Wavelength Demultiplexer Using
`Both Interference Filters and a Diffraction Grating, Euro
`pean Conference of Optical Communications, Conference
`Proceedings (Sep. 8—11, 1981).
`J. Conradi et al., Laser Based WDM Multichannel Video
`Transmission System, Electronic Letters, vol. 17, No. 2 (Jan.
`22, 1981).
`J. Laude et al., Wavelength division multiplexing/demulti
`plexing (WDM) using diffraction gratings, SPIE, vol. 503,
`Application, Theory, and Fabricationof Periodic Structures
`(1984) (No month available).
`A. Livanos et al., Chirped—grating demulitplexer in dielec
`tric Waveguides, Applied Physics Letters, vol. 30, No. 10
`(May 1977).
`H. Obara et al., Star Coupler Based WDM SWitch Employ
`ing Tunable Devices With Reduced Tunability Range, Elec
`tronic Letters, vol. 28, No. 13 (Jun. 1992).
`A. Willner et al., 2—D WDM Optical Interconnections Using
`Multiple—Wavelength VCSEL’s for Simultaneous and
`Recon?gurable Communication Among Many Planes, IEEE
`Phoyonics Technology Letters, vol. 5, No. 7 (Jul. 1993).
`
`M. Wang et al., Five Channel Polymer Waveguide Wave
`length Division Demultiplexer for the NeW Infrared, IEEE
`Photonics Technology Letters, vol. 3, No. 1 (Jan. 1991).
`M. Li et al., TWo—channel surface—normal Wavelength
`demultiplexer using substrate guided Waves in conjunction
`With multiplexed Waveguide holograms, Appl. Phys. Lett.,
`vol. 66, No. 3 (Jan. 1995).
`J. Laude et al., Stimax, A Grating Multiplexer for Mono
`mode or Multimode Fibers, Ninth European Conference on
`Optical Communicaton—ECOC83, Geneva, SWitZerland
`(Oct. 23—26, 1983).
`W.J. Tomlinson, “Wavelength multiplexing in multimode
`optical ?bers”, Applied Optics, vol. 16, No. 8, pp.
`2180—2194 (Aug. 1977).
`AC. Livanos et al, “Chirped—grating demultiplexers in
`dielectric Waveguides”, Applied Physics Letters, vol. 30,
`No. 10, pp. 519—521 (May 15, 1977).
`Hideki Ishio et al, “RevieW and status of Wavelength—divi
`sion multiplexing technology and its application”, Journal of
`LightWave Technology, vol. LT—2, No. 4, pp. 448—463 (Aug.
`1984).
`H. Obara et al, “Star coupler based WDM sWitch employing
`tunable devices With reduced tunability range”, Electronic
`Letters, vol. 28, No. 13, pp. 268—270 (Jun. 18, 1992).
`AE Willner et al, “2—D WDM optical interconnections
`using multiple—Wavelength VCSEL’s for simultaneous and
`recon?gurable communication among many planes”, IEEE
`Photonics Technology Letters, vol. 5, No. 7, pp. 838—841
`(Jul. 1993).
`Yang—Tang Huang et al, “Wavelength—division—multiplex
`ing and —demeltiplexing by using a substrate—mode grating
`pair”, Optics Letters, vol. 17, No. 22, pp. 1629—1631 (Nov.
`15, 1992).
`MR. Wang et al, “Five—channel polymer Waveguide divi
`sion demultilexer for the near infrared”, IEEE Photonics
`Technology Letters, vol. 3, No. 1, pp. 36—38 (Jan. 1991).
`Maggie M. Li et al, “TWo—channel surface—normal Wave
`length division demultiplexer using substrate guided Waves
`in conjunction With multiplexed Waveguide holograms”,
`Appl. Phys. Lett. vol. 66, No. 3, pp. 262—264 (Jan. 16, 1995).
`
`Petitioner Ciena Corp. et al.
`Exhibit 1021-3
`
`

`

`U.S. Patent
`
`Jan. 4,2000
`
`Sheet 1 0f8
`
`6,011,884
`
`of
`
`wow
`
`NF
`
`NW
`
`9
`
`ow
`
`Petitioner Ciena Corp. et al.
`Exhibit 1021-4
`
`

`

`U.S. Patent
`
`Jan. 4,2000
`
`Sheet 2 0f8
`
`6,011,884
`
`mNUE
`
`on
`
`Petitioner Ciena Corp. et al.
`Exhibit 1021-5
`
`

`

`U.S. Patent
`
`Jan. 4,2000
`
`Sheet 3 0f8
`
`6,011,884
`
`or ow
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`
`Petitioner Ciena Corp. et al.
`Exhibit 1021-6
`
`

`

`U.S. Patent
`US. Patent
`
`Jan. 4, 2000
`Jan. 4,2000
`
`Sheet 4 0f 8
`Sheet 4 0f8
`
`6,011,884
`6,011,884
`
`FIG.4
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`Petitioner Ciena Corp. et 21].
`Exhibit 1021-7
`
`Petitioner Ciena Corp. et al.
`Exhibit 1021-7
`
`

`

`U.S. Patent
`
`Jan. 4,2000
`
`Sheet 5 0f8
`
`6,011,884
`
`FIG.5C
`
`FIG.5A
`
`Petitioner Ciena Corp. et al.
`Exhibit 1021-8
`
`

`

`U.S. Patent
`US. Patent
`
`Jan. 4,2000
`Jan. 4,2000
`
`Sheet 6 0f8
`Sheet 6 0f8
`
`6,011,884
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`
`Petitioner Ciena Corp. et 21].
`Exhibit 1021-9
`
`Petitioner Ciena Corp. et al.
`Exhibit 1021-9
`
`

`

`U.S. Patent
`US. Patent
`
`Jan. 4, 2000
`Jan. 4,2000
`
`Sheet 7 0f 8
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`Exhibit 1021-10
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`
`Petitioner Ciena Corp. et al.
`Exhibit 1021-10
`
`

`

`US. Patent
`
`Jan. 4,2000
`
`Sheet 8 0f8
`
`6,011,884
`
`FIG.8
`
`Petitioner Ciena Corp. et 21].
`Exhibit 1021-11
`
`Petitioner Ciena Corp. et al.
`Exhibit 1021-11
`
`

`

`6,011,884
`
`1
`INTEGRATED BI-DIRECTIONAL AXIAL
`GRADIENT REFRACTIVE INDEX/
`DIFFRACTION GRATING WAVELENGTH
`DIVISION MULTIPLEXER
`
`CROSS-REFERENCE TO RELATED
`APPLICATIONS
`
`The present application is related to tWo other patent
`applications, the ?rst entitled “Integrated Bi-Directional
`Dual Axial Gradient Refractive Index/Diffraction Grating
`Wavelength Division Multiplexer,” Ser. No. 08/990,199, and
`the second entitled “Integrated BiDirectional Gradient
`Refractive Index Wavelength Division Multiplexer” Ser. No.
`08/990198, both ?led on even date hereWith and assigned to
`the same assignee. This and the tWo related applications are
`all directed to Wavelength division multiplexers, and differ
`in the presence or absence of a diffraction grating and the
`number of gradient refractive index elements.
`
`TECHNICAL FIELD
`
`10
`
`15
`
`20
`
`The present invention relates generally to axial gradient
`refractive index lenses, and, more particularly, to axial
`gradient refractive index lenses employed in Wavelength
`division multiplexing applications.
`
`25
`
`BACKGROUND ART
`
`2
`initially spatially separated in space—and provides a means
`of spatially combining all of the different Wavelength beams
`into a single polychromatic beam suitable for launching into
`an optical ?ber. The multiplexer may be a completely
`passive optical device or may indude electronics that control
`or monitor the performance of the multiplexer. The input of
`the multiplexer is typically accomplished With optical ?bers;
`hoWever, laser diodes or other optical sources may be
`employed. The output of the multiplexer is typically an
`optical ?ber.
`Similarly, the second device for WDM is a Wavelength
`division demultiplexer. This device is functionally the oppo
`site of the multiplexer; it receives a polychromatic beam
`input from an optical ?ber and provides a means of spatially
`separating the Wavelengths. The output of the demultiplexer
`is typically interfaced to optical ?bers or to photodetectors.
`During the past 20 years, various types of WDMs have
`been proposed and demonstrated; see, e.g., (1) W. J.
`Tomlinson, Applied Optics, Vol. 16, No. 8, pp. 2180—2194
`(August 1977); (2) A. C. Livanos et al, Applied Physics
`Letters, Vol. 30, No. 10, pp. 519—521 (May 15, 1977); (3) H.
`Ishio et al, Journal of Lightwave Technology, Vol. 2, No. 4,
`pp. 448—463 (August 1984); (4) H. Obara et al, Electronics
`Letters, Vol. 28, No. 13, pp. 1268—1270 (Jun. 18, 1992); (5)
`A. E. Wiliner et al, IEEE Photonics Technology Letters, Vol.
`5, No. 7, pp. 838—841 (July 1993); and (6) Y. T. Huang et al,
`Optics Letters, Vol. 17, No. 22, pp. 1629—1631 (Nov. 15,
`1992).
`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 of channels, and narroW channel
`spacing.
`
`DISCLOSURE OF 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 demultiplexer due to the symmetry of the
`multiplexer and demultiplexer function. The multiplexer
`device of the present invention comprises:
`(a) a means for accepting a plurality of optical input
`beams containing at least one Wavelength from optical
`?bers 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 optical ?bers or integration of
`other devices;
`(b) 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 tilted
`back surface;
`(c) a near-LittroW diffraction grating operatively associ
`ated With the homogeneous index boot lens, formed or
`affixed at the planar exit surface of the coupler sub
`system Which combines a plurality of spatially sepa
`rated Wavelengths into at least a single polychromatic
`optical light beam and re?ects the combined optical
`
`30
`
`35
`
`40
`
`45
`
`55
`
`Wavelength division multiplexing (WDM) is a rapidly
`emerging technology that enables a very signi?cant increase
`in the aggregate volume of data that can be transmitted over
`optical ?bers. Traditionally, most optical ?bers 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 ?ber. 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 ?ber are loW. Today,
`commercial WDM systems exist that alloW transmission of
`2 to 32 simultaneous channels.
`WDM is a cost-effective method of increasing the volume
`of data (commonly termed bandWidth) transferred over
`optical ?bers. Alternate competing technologies to increas
`ing bandWidth include the burying of additional ?ber optic
`cable or increasing the transmission speed on optical ?ber.
`The burying of additional ?ber 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 ?ber optic
`system. One of the primary strategies to electronically
`increasing bandWidth has been to use time division multi
`plexing (TDM), 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 effective for increasing bandWidth; hoWever, it is noW
`increasingly dif?cult to improve transmission speeds, both
`from a technological and economical standpoint. WDM
`offers the potential of both an economical and technological
`solution to increasing bandWidth by using many parallel
`60
`channels. WDM is complimentary to TDM, that is, WDM
`can alloW many simultaneous high transmission rate TDM
`channels to be passed over a single optical ?ber.
`The use of WDM to increase bandWidth requires tWo
`basic devices that are conceptually symmetrical. The ?rst
`device is a Wavelength division multiplexer. This device
`takes multiple beams—each With discrete Wavelengths and
`
`65
`
`Petitioner Ciena Corp. et al.
`Exhibit 1021-12
`
`

`

`6,011,884
`
`15
`
`3
`beam back into the coupler subsystem at essentially the
`same angle as the incident beams;
`(d) an optional array of electrooptical elements for refract
`ing the plurality of Wavelengths to provide channel
`routing or sWitching capabilities; and
`(e) a means of outputting at least one multiplexed, poly
`chromatic output beam for at least one optical ?ber,
`said means being located at the same input sur face in
`(a).
`The 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 demultiplexer for applications such as net
`Work hubs or intersections that distribute channels to various
`areas of a netWork. The axial gradient refractive index and
`diffraction grating-based WDM devices of the present
`invention are unique because they contain one or more
`homogeneous index boot 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 diffraction-limited 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 collimating performance is the same, but it is
`exceedingly dif?cult to create a one-piece, integrated device
`With aspheric surfaces. Further, aspherical lenses are typi
`cally very costly and suffer from ghosting-types of re?ec
`tions Which are very undesirable.
`The integration of the WDM device alloWs for a compact,
`robust, and environmentally and thermally stable system. In
`particular, integration 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 WDM approaches that use interference
`?lter-based or ?ber Bragg gratings. Such serial WDM
`approaches suffer from signi?cant optical loss, crosstalk,
`55
`alignment, and temperature issues. Further, compared to
`other parallel multiplexing approaches such as array
`Waveguide grating devices, fused ?ber 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
`
`4
`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 OF THE DRAWINGS
`The draWings referred to in this description should be
`understood as not being draWn to scale except if speci?cally
`noted.
`FIG. 1 is a side elevational schematic vieW (FIG. 1a) and
`a top plan schematic vieW (FIG. 1b) of a Wavelength
`division multiplexer device of the present invention, With an
`axial gradient refractive index lens, near-LittroW diffraction
`grating, and multiple optical ?ber inputs multiplexed to one
`optical ?ber 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. 2b is a perspective vieW of the input portion of the
`device of FIG. 1, illustrating an alternate input con?guration
`in Which the input is an array of laser diodes;
`FIG. 2c is a perspective vieW of a portion of the device of
`FIG. 1, illustrating an alternate output con?guration for a
`demultiplexer device in Which the output is an array of
`photodetectors;
`FIG. 3 is a side elevational 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 of electrooptical beamsteering
`elements (parallel to the grating direction) to individually
`beamsteer each input channel to an output ?ber port;
`FIGS. 5a—5c are plots on coordinates of intensity and
`Wavelength, depicting different intensity pro?les for differ
`ent con?gurations of the multiplexer of the present inven
`tion;
`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 beamsteer each input chan
`nel to an output ?ber 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
`trooptical beamsteering element to individually bearnsteer
`each input channel to an output ?ber port; and
`FIG. 8 is a perspective vieW of a portion of the device of
`FIG. 1, but employing tWo multiplexers to perform a chan
`nel blocking function by incorporating an electrooptical
`blocking array on the input face of one multiplexer.
`
`BEST MODES FOR CARRYING OUT THE
`INVENTION
`Reference is noW made in detail to speci?c embodiments
`of the present invention, Which illustrate the best modes
`presently contemplated by the inventors for practicing the
`invention. Alternative embodiments are also brie?y
`described as applicable.
`FIG. 1 depicts tWo vieWs of a preferred embodiment of
`the present invention, Which embodies an axial gradient
`refractive index/diffraction grating Wavelength division
`multiplexer device. Speci?cally, FIG. 1a illustrates the side
`elevational vieW of the device, While FIG. 1b illustrates the
`top plan vieW.
`
`25
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`35
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`45
`
`65
`
`Petitioner Ciena Corp. et al.
`Exhibit 1021-13
`
`

`

`6,011,884
`
`5
`The device 10 of the ?rst embodiment takes an input ?ber
`array 12 of N discrete Wavelengths of light 14 and spatially
`combines them into a single optical beam 16 and outputs the
`single beam to a single optical ?ber 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.
`The device 10 further comprises a coupler element 20; on
`the exit surface 20b of the coupler element is formed or
`placed a near-LittroW diffraction grating 22. The near
`LittroW diffraction grating 22 provides both the function of
`angularly dispersing optical beams of differing Wavelength
`and re?ecting the optical beams back 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 of Which depends
`upon the Wavelength of each incident optical beam. Further,
`the diffraction grating 22 is oriented at a special angle
`relative to the optical axis of the device 10 in order to obtain
`the LittroW 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 re?ected 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 diffraction grating is used to obtain near-LittroW
`diffraction for each of the plurality of Wavelengths present.
`The LittroW diffraction angle is determined by the Well
`knoWn formula
`
`Where m is the diffraction order, 7» is the Wavelength, d is the
`diffraction grating groove spacing, and (X,- is the same
`incident and diffracted angle. It 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 20 comprises a ?rst homogeneous
`index boot lens 24 joined or