Coherent light generators – Particular beam control device – Producing plural wavelength output
Reexamination Certificate
2002-04-25
2004-10-05
Wong, Don (Department: 2828)
Coherent light generators
Particular beam control device
Producing plural wavelength output
C372S020000, C349S029000, C398S201000
Reexamination Certificate
active
06801551
ABSTRACT:
BACKGROUND AND PRIOR ART
Multiwavelength generation lasers have been increasingly demonstrated over the past several years. For example, the subject invention assignee as been at the forefront of developing multiwavelength modelocked semiconductor diode lasers. See for example, Shi et al. Four-wavelength, 10-GHZ pico second pulse generation from an active modelocked single-stripe diode laser, Conference proceeding presentation on May 18-23, 1997, OSA Technical Technical Digest Series Vol. 11, Conference on Lasers and Electrooptics(CLEO), 1997); and OSA Trends in Optics and Photonics, Vol. 13 of Ultrafast Electronics and Optoelectronics, Conference Proceedings of March 17-19, 1997.
Wavelength division multiplexing in telecommunication and data transmission systems increases system capacity by more fully taking advantage of the intrinsic bandwidth of installed optical fiber. Channel widths and spacings have been standardized so those necessary system components such as lasers and spectrally dispersive components can be designed for interoperability. Simultaneously, the data rate of individual channels is being pushed toward higher rates with approximately 10 Gbit standards (both Sonet and Ethernet) near deployment. Current architectures utilize a separate laser for each wavelength channel introducing complexity and cost issues. Significant research has been conducted to develop and assess potential multi-wavelength sources for WDM systems. Multiple active device arrays of both laser diodes and VCSELs have been constructed and tested but problems with growth control toward exact spectral emission remains a concern. See Kudo, K., Furushima, Y., Nakazaki, T., Yamaguchi, M., “Multiwavelength microarray semiconductor lasers”,
Electron. Lett
., v 34n 21 Oct. 15, 1998. P. 2037-2038. Continuum generation in optical fibers from high power pulsed sources followed by spectral filtering has been demonstrated but suffers from the need for the high power front end as well as the power inefficiency of discarding much of the generated spectrum in the filtering process. See Morioka, T., Mori, K., Kawanishi, S., Saruwatari, M., “Multi-WDM-channel, Gbit/s pulse generation from a single laser source utilizing LD pumped supercontinuum in optical fibers”,
IEEE Photonics Tech. Lett
., v 6 n 3 March 1994. P 365-368.
Multiple quantum well devices with individually shifted spectral gain have also been constructed and utilized downstream spectral filtering with the attendant power inefficiencies. See Coudenys, G., Moerman, I., Zhu, Y., Van Daele, P., Demeester, P., “Multiwavelength InGaAs/InGaAsP strained layer MQW laser array using shadow masked growth”,
IEEE Photonics Tech. Lett
., v 4n 6 June 1992, p 524-526. Cavities based on various grating technologies, Zhu, B., White, I., “Multiwavelength picosecond optical pulse generation using an actively modelocked multichannel grating cavity laser”,
Journal of Lightwave Tech
., v 13 n 12 December 1995, p 2327-2335, and erbium fiber ring cavities with distributed fiber gratings or etalons have also been demonstrated. See Papkyriakopoulos, T., Stavdas, A., Protonotarios, E., Avramopoulos, H., “10×10 GHz Simultaneously modelocked multiwavelength fibre ring laser”,
Electron. Lett
., 1999, 35, (2), p 179-181 and Chow, J., Town, G., Eggleton, B., Ibsen, M., Sugden, K., Bennion, I., “Multiwavelength generation in an erbium doped fiber laser using in fiber comb filters”,
IEEE Photonics Tech. Lett
., v 8n 1January 1996, p 60-62.
A common problem with current multiwavelength generation systems is that the individual channels often generate multiwavelengths having different amplitude(intensity) values.
In addition to the subject assignee's contributions, over the years various attempts have been made for generating multiwavelength lasers. See for example, U.S. Pat. No. 6,018,536 to Alphonse; U.S. Pat. No. 6,061,369 to Conradi; U.S. Pat. No. 6,064,681 to Ackerman; U.S. Pat. No. 6,192,058 to Abels; U.S. Pat. No. 6,275,511 to Pan et al. However, none of the known prior art overcomes the problems of consistently and actively preventing uneven amplitude values for each of the multiwavelength channels.
SUMMARY OF THE INVENTION
A primary objective of the subject invention is to provide a multiwavelength laser system that evens out intensity(amplitude) values of each channel.
A secondary objective of the subject invention is to provide a multiwavelength laser system that provides for computer control within the laser cavity.
A third objective of the subject invention is to provide a multiwavelength laser system having multiple wavelength channels that can be independently controlled in amplitude.
A fourth objective of the subject invention is to provide a multiwavelength laser system having multiple wavelength channels that can be independently controlled in phase.
A fifth objective of the subject invention is to provide a multiwavelength laser system having multiple wavelength channels that can be independently controlled in both amplitude and phase.
A programmable multiwavelength laser systems and methods include simultaneously generating multiwavelength channels with a modelocked diode laser and controller for automatically controlling amplitude levels of each of the channels from a Semiconductor Optical Amplifier(SOA) ring laser configuration. The system and method can include up to approximately three(3), seven(7), ten(10), twelve(12), fourteen(14) and sixteen(16) channels. The controller can be located in a closed loop inside of the laser cavity and include a computer, and a spatial light modulator(SLM) connected to gratings, wherein the computer adjusts transmission of each liquid pixel in the SLM to optimize, equalize and maximize power in each output channel, and the controller can control both phase and amplitude levels of each of the channels so that each of the channels can have substantially identical intensity levels.
Spectral flatness of multiwavelength emissions from the Semiconductor Optical Amplifier(SOA) ring laser configuration can be controlled by a programmable liquid crystal spatial light modulator(SLM) based on spectrally monitoring individual wavelength intensities of the laser output. A spectrally equal amplified output can also occur by pre-distorting the laser to account for amplifier spectral gain dependence.
Further objects and advantages of this invention will be apparent from the following detailed description of a presently preferred embodiment which is illustrated schematically in the accompanying drawings.
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Croeze Trino
Delfyett Peter
Park Eric
Jackson Cornelius H
Law Offices of Brian S. Steinberger , P.A.
Steinberger Brian S.
University of Central Florida
Wong Don
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