Fault-tolerant fiber-optical multiwavelength processor

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FAULT-TOLERANT FIBER-OPTICAL
MULTIWAVELENGTH PROCESSOR

This application claims the benefit of U.S. provisional patent application, Ser. No. 60/292,249, filed May 18, 2001. 5

FIELD OF INVENTION

This invention relates to fiber-optic (FO) processors using micromirror controls and, more particularly, to macro-pixel optical MEMS device-based FO processor structures used for implementing add-drop wavelength routing, 2x2 crossconnect switching, and wavelength optical gain controls for light signal processing in various optical networks such as wavelength division multiplexed (WDM) optical communications, distributed sensor networks, and photonic signal processing systems requiring optical routing and gain control.

BACKGROUND OF INVENTION

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It is well known that an excellent choice for light control is via the use of mirrors. Mirrors provide high reflectivity over broad bandwidths, as desired in WDM systems. Today, an excellent method for making actively controlled mirrors is via microelectromechanical system (MEMS) technology 25 that promises to offer low cost compact optical modules via the use of low cost batch fabrication techniques similar to semiconductor electronic chip production methods. MEMS technology has been previously proposed to realize fiber optic beam control modules. 30

Various FO switches have been proposed using optical MEMS technology. The include 2x2 structures, wavelength add-drop (A-D) filters, and NxN crossconnects. For example, 2x2 type switches have been described in M. F. Dautartas, A. M. Benzoni, Y. C. Chen, G. E. Blonder, B. H. 35 Johnson, C. R. Paola, E. Rice, and Y.-H. Wong, "A siliconbased moving-mirror optical switch," Journal of Lightwave Technology, Vol. 10, No. 8, pp. 1078-1085, August 1992; and N. A. Riza and D. L. Polla, "Microdynamical fiber-optic switch," U.S. Pat. No. 5,208,880, May 4,1993, FO switches 40 are proposed using the electronically controlled actuation of a single micromirror fabricated using micromaching techniques used in MEMS chip fabrication. More recently, others have used this "single micromirror per optical beam" control approach to realize lxN and 2x2 switches. These 45 works using MEMS or other mechanical means are described in W. J. Tomlinson and R. E. Wagner, "Optical switch," U.S. Pat. No. , 4,208,094, Jun. 17, 1980; H. J. Ramsey and M. L. Dakss, "Piezoelectric optical switch," U.S. Pat. No. , 4,303,302, Dec. 1, 1981; T. Tanaka, Y. 50 Tsujimoto, H. Serizawa, and K. Hattori, "Optical switching device," U.S. Pat. No. 4,304,460, Dec. 8,1981; J. -P. Laude, "Switching device between optical fibers," U.S. Pat. No. 4,484,793, Nov. 27,1984; F. H. Levinson, "Optical coupling device utilizing a mirror and cantilevered arm," U.S. Pat. 55 No. 4,626,066, Dec. 2, 1986; G. E. Blonder, "Radiation switching arrangement with moving deflecting element," U.S. Pat. No. 4,932,745, Jun. 12, 1990; A. M. Benzoni, "Magnetic activation mechanism for an optical switch," U.S. Pat. No. 5,042,889, Aug. 27, 1991; G. A. Magel and T. 60 G. McDonald, "Optical switch using spatial light modulators," U.S. Pat. No. 5,155,778, Oct. 13, 1992; G. A. Magel, "Fiber optic switch with spatial light modulator device," U.S. Pat. No. 5,199,088, Mar. 30, 1993; J. J. Pan, "lxN Electromechanical optical switch," U.S. Pat. No. 65 5,359,683, Oct. 25, 1994; M. Ghezzo, C. P. Yakymyshyn, and A. R. Duggal, "Integrated microelectromechanical poly

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meric photonic switching arrays," U.S. Pat. No. 5,367,584, Nov. 22,1994; J. E. Ford, "Fiber optic switching device and method using free space scanning," U.S. Pat. No. 5,621,829, Apr. 15,1997; L. Yang, G. R. Trott, K. Shubert, K. Salomaa, and K. W. Carey, "Mechanical fiber optic switch," U.S. Pat. No. 5,699,463, Dec. 16, 1997; T. G. McDonald, "Using an asymmetric element to create a lxN optical switch," U.S. Pat. No. 5,774,604, Jun. 30,1998; J.-J. Pan, J.-Y. Xu, and C. J.-L. Yang, "Efficient electromechanical optical switches," U.S. Pat. No. 5,838,847, Nov. 17, 1998; V. A. Aksyuk, D. J. Bishop, J. E. Ford, and J. A. Walker, "Freespace optical bypass-exchange switch," U.S. Pat. No. 5,943,454, Aug. 24, 1999; V. A. Aksyuk, D. J. Bishop, and C. Randy, "Micromachined optical switch with tapered ends," U.S. Pat. No. 6,108,466, Aug. 22, 2000.

Other related works on switching includes E. Oilier, C. Chabrol, T. Enot, P. Brunet-Manquat, J. Margail, and P. Mottier, "1x8 Micro-mechanical switches based on moving waveguides for optical fiber network switching," 2000 IEEE/LEOS International Conference on Optical MEMS, pp. 39-40, Kauai, Hi., August 2000; R. T. Chen, H. Nguyen, and M. C. Wu, "A high-speed low-voltage stress-induced micromachined 2x2 optical switch," IEEE Photonics Technology Letters, Vol. 11, No. 11, pp. 1396-1398, November 1999; S. Nagaoka, "Compact latching-type single-modefiber switches fabricated by a fiber-micromachining technique and their practical applications," IEEE Journal of Selected Topics in Quantum Electronics, Vol. 5, No. 1, pp. 36-45, January/February 1999; A. A. Yasseen, J. N. Mitchell, J. F. Klemic, D. A. Smith, and M. Mehregany, "A rotary electrostatic micromirror 1x8 optical switch," IEEE Journal of Selected Topics in Quantum Electronics, Vol. 5, No. 1, pp. 26-32, January/February 1999; H. Toshiyoshi, D. Miyauchi, and H. Fujita, "Electromagnetic torsion mirrors for self-aligned fiber-optic crossconnectors by silicon micromachining," IEEE Journal of Selected Topics in Quantum Electronics, Vol. 5, No. 1, pp. 10-17, January/February 1999; M. Makihara, M. Sato, F. Shimokawa, and Y. Nishida, "Micromechanical optical switches based on fhermocapillary integrated in waveguide substrate," Journal of Lightwave Technology, Vol. 17, No. 1, pp. 14-18, January 1999; S.-S. Lee, L. S. Huang, C.-J. Kim, and M. C. Wu, "Freespace fiber-optic switches based on MEMS vertical torsion mirrors," Journal of Lightwave Technology, Vol. 17, No. 1, pp. 7-13, January 1999; C. Marxer and N. F. de Rooij, "Micro-opto-mechanical 2x2 switch for single-mode fibers based on plasma-etched silicon mirror and electrostatic actuation," Journal of Lightwave Technology, Vol. 17, No. 1, pp. 2-6, January 1999; J. E. Ford and D. J. DiGiovanni, "lxN Fiber bundle scanning switch," IEEE Photonics Technology Letters, Vol. 10, No. 7, pp. 967-969, July 1998; V. Aksyuk, B. Barder, C. R. Giles, R. Ruel, L. Stulz, and D. Bishop, "Low insertion loss packaged and fibre connectorised MEMS reflective optical switch," Electronics Letters, Vol. 34, No. 14, pp. 1413-1414, July 1998; C. Marxer, C. Thio, M.-A. Gretillat, N. F. de Rooij, R. Battig, O. Anthamatten, B. Valk, and P. Vogel, "Vertical mirrors fabricated by deep reactive ion etching for fiber-optic switching applications," Journal of Microelectromechanical Systems, Vol. 6, No. 3, pp. 277-285, September 1997; R. A. Miller, Y. C. Tai, G. Xu, J. Bartha, and F. Lin, "An electromagnetic MEMS 2x2 fiber optic bypass switch," Transducers'97, pp. 89-92, Chicago, III, June 1997; S. S. Lee, E. Motamedi, and M. C. Wu, "Surface-micromachined free-space fiber optic switches with integrated microactuators for optical fiber communication systems," Transducers'97, pp. 85-87, Chicago, 111., June 1997; H. Toshiyoshi and H. Fujita, "Electrostatic micro torsion mirrors for an optical switch matrix," Journal of Microelectromechanical Systems, Vol. 5, No. 4, pp. 231-237, December 1996; S. S. Lee, L. Y. Lin, and M. C. Wu, "Surfacemicromachined free-space fibre-optic switches," Electronics 5 Letters, Vol. 31, No. 17, pp. 1481-1482, August 1995; L. A. Field, D. L. Burriesci, P. R. Robrish, and R. C. Ruby, "Micromachined 1x2 optical fiber switch," Transducers'95, pp. 344-347, Stockholm, Sweden, June 1995; R. M. Boysel, T. G. McDonald, G. A. Magel, G. C. Smith, and J. L. 10 Leonard, "Integration of deformable mirror devices with optical fibers and waveguides," Proceedings of SPIE, Vol. 1793, pp. 34-39, 1992; K. Hogari and T. Matsumoto, "Electrostatically driven micromechanical 2x2 optical switch," Applied Optics, Vol. 30, No. 10, pp. 1253-1257, 15 April 1991; K. Hogari and T. Matsumoto, "Electrostatically driven fiber-optic micromechanical on/off switch and its application to subscriber transmission systems," Journal of Lightwave Technology, Vol. 8, No. 5, pp. 722-727, May 1990. 20

Add-drop switches have also been proposed using MEMS. For instance, one such switching module is described in W. J. Tomlinson, "Wavelength-selective optical add/drop using tilting micromirrors," U.S. Pat. No. 5,960, 133, Sep. 28, 1999; J. E. Ford, J. A. Walker, V. Aksyuk, and 25 D. J. Bishop, "Wavelength selectable add/drop with tilting micromirrors," IEEE LEOS Annual Mtg., IEEE, N.J., postdeadline paperPD2.3, November 1997, where apart from the limitations of using a single micromirror per beam, this 4-port switch is not reversible and does not form a 2x2 30 switch that can be used to form larger NxN switch matrices. Other examples of add-drop switches using MEMS includes V. A. Aksyuk, B. P. Barber, D. J. Bishop, P. I. Gammel, C. R. Giles, "Micro-opto-mechanical devices and method thereof," U.S. Pat. No. 5,995,688, Nov. 30, 1999; C. R. 35 Giles, B. Barber, V. Aksyuk, R. Ruel, L. Stulz, D. Bishop "Reconfigurable 16-channel WDM drop module sing silicon MEMS optical switches," IEEE Photonics Technology Letters, Vol. 11, No. 1, pp. 63-65, January 1999; V. A. Aksyuk, D. J. Bishop, J. E. Ford, R. E. Slusher, "Article 40 comprising a wavelength selective add-drop multiplexer," U.S. Pat. No. 5,974,207, Oct. 26, 1999; C. Pu, L. Y. Lin, E. L. Goldstien, R. W. Tkach, "Micro-machined optical add/ drop multiplexer with client configurability," 2000 IEEEI LEOS International Conference on Optical MEMS, pp. 45 35-36, Aug. 21-24, 2000. Similarly, in S. Glockner, R. Goring, and T. Possner, "Micro-opto-mechanical beam deflectors," Optical Engineering, Vol. 36, No. 5, pp. 1339-1345, May 1997; P. M. Hagelin, U. Krishnamoorthy, J. P. Heritage, O. Solgaard, "Scalable optical cross-connect 50 switch using micromachined mirrors," IEEE Photonics Technology Letters, Vol. 12, No. 7, pp. 882-884, July 2000; and L. Y. Lin, E. L. Goldstein, and R. W. Tkach, "Free-space micromachined optical switches with submillisecond switching time for large-scale optical crossconnects," IEEE 55 Photonics Technology Letters, Vol. 10, No. 4, pp. 525-527, April 1998, a single micromirror per beam that can be rather large in size is used, leading to slow millisecond range switching speeds.

Other mechanically implemented optical crossconnects 60 are described in P. M. Hagelin, U. Krishnamoorthy, J. P. Heritage, O. Solgaard, "Scalable optical cross-connect switch using micromachined mirrors," IEEE Photonics Technology Letters, Vol. 12, No. 7, pp. 882-884, July 2000; H. Laor, "Compact optical matrix switch with fixed location 65 fibers," U.S. Pat. No. 6,097,860, Aug. 1, 2000; O. Solgaard, J. P. Heritage, and A. R. Bhattaral, "Multi-wavelength

cross-connect optical switch," U.S. Pat. No. 6,097,859, Aug. 1, 2000; M. T. Fatchi and J. E. Ford, "Free-space optical signal switch arrangement," U.S. Pat. No. 6,002,818, Dec. 14, 1999; R. L. Jungerman and D. M. Braun, "Optical cross-connect switch using a pin grid actuator," U.S. Pat. No. 5,841,917, Nov. 24, 1998; F. H. Levinson, "Optical matrix switch," U.S. Pat. No. 4,580,873, Apr. 8, 1986; G. J. G. Broussaud, "Optical switch for a very large number of channels," U.S. Pat. No. 4,365,863, Dec. 28, 1982; T.-K. Koo, "Optoelectronic data entry means having plurality of control means to direct part of radiation in channel from radiation source to output channel," U.S. Pat. No. 3,548,050, Mar. 7, 1972; D. T. Neilson, V. A. Aksyuk, S. Arney, N. R. Basavanhally, K. S. Bhalla, D. J. Bishop, B. A. Boie, C. A. Bolle, J. V. Gates, A. M. Gottlieb, J. P. Hickey, N. A. Jackman, P. R. Kolodner, S. K. Korotky, B. Mikkelson, F. Pardo, G. Raybon, R. Ruel, R. E. Scotti, T. W. Van Blarcum, L. Zhang, and C. R. Giles, "Fully provisioned 112x112 micro-mechanical optical crossconnect with 35.8 Tb/s demonstrated capacity," OFC Technical Digest, Postdeadline, pp.PD12-l-PD12-3, Baltimore, Md., March 2000; H. Laor, J. D'Entremont, E. Fontenot, M. Hudson, A. Richards, and D. Krozier, "Performance of a 576x576 optical cross connect," National Fiber Optic Engineers Conference, pp. 276-281, Chicago, 111. September 1999; L. Y. Lin, E. L. Goldstein, J. M. Simmons, and R. W. Tkach, "High-density micromachined polygon optical crossconnects exploiting network connection-symmetry," IEEE Photonics Technology Letters, Vol. 10, No. 10, pp. 1425-1427, October 1998.

Single pixel per beam MEMS-based variable FO attenuators have also been proposed such as described in J. E. Ford and J. A. Walker, "Dynamic spectral power equalization using micro-opto-mechanics," IEEE Photonics Technology Letters, Vol. 10, No. 10, pp. 1440-1442, October, 1998, V. Askyuk, B. Barber, C. R. Giles, R. Ruel, L. Stulz, and D. Bishop, "Low insertion loss packaged and fibre connectorized MEMS reflective optical switch," IEE Electronics Lett., Vol. 34, No. 14, pp. 1413-1414, Jul. 9,1998, and B. Barber, C. R. Giles, V. Askyuk, R. Ruel, L. Stulz, and D. Bishop, "A fiber connectorized MEMS variable optical attenuator," IEEE Photon. Technol. Lett, Vol. 10, No. 9, pp. 1262-1264, September 1998. Apart from the tolerance limited single pixel control approach, attenuation control in these modules is implemented in an analog fashion by carefully moving a micromirror per beam (or wavelength) through a continuous range of positions. For instance, in both the cited V. Askyuk, et.al. designs, a micromirror is linearly translated to partially block a beam and hence cause attenuation. In the J. Ford, et.al. design case, a micromirror is translated through many small sub-micron size steps to form a varying reflection surface, and this ultra-small motion makes the module very sensitive to vibrations. Thus, extensive module calibration and costly and complex control electronics are required to maintain the high performance of these analog-type FO MEMS-based modules. Other related works on mechanical or MEMS based VOAs are described in works such as V. A. Aksyuk, D. J. Bishop, P. L. Gammel, C. R. Giles, "Article comprising a light actuated micromechanical photonic switch," U.S. Pat. No. 6,075,239, Jun. 13, 2000; E. E. Bergmann, D. J. Bishop, "Moving mirror switch," U.S. Pat. No. 6,031,946, Feb. 29, 2000; P. Colbourne, J. Obhl, N. Teltelbaum, "Variable optical attenuator," U.S. Pat. No. 5,915,063, Jun. 22, 1999; J. E. Ford, K. W. Goossen, "Level setting optical attenuator," U.S. Pat. No. 5,900,983, May 4, 1999; C. M. Garrett, C Fan, D. Cugalj, D. Gransden, "Voltage controlled attenuator," U.S. Pat. No. 5,745,634, Apr. 28, 1998; J. E. Ford, D. A. B. Miller, M. C. Nuss, J. A.