DETAILS OF THE ACHIEVEMENT
All-optical gain-clamping technique for lumped Raman fibre amplifiers
Miroslav Karásek, DSc.; Jiří Kaňka, Ph.D.; Pavel Honzátko, Ph.D.; Jan Radil, Ph.D.
Year: 2003
The capacity that can be provided by long-haul transmission systems has been boosted during the last few years by the use of optical wavelength division multiplexing techniques (WDM). Currently, WDM systems have reached a stage where several hundreds of channels are considered, with bit rates of 10 Gbit/s, 40 Gbit/s or even more in the labs. This evolution has been enabled owing to new technologies such as wideband optical amplifiers. Wavelength based routing has been proposed as a promising approach towards transparent all-optical WDM networking. When conventional fibre amplifiers are used, such networks would be vulnerable to transient inter-channel cross-gain modulation when they undergo dynamic reconfigurations. We have suggested an application of all-optical gain-clamping (AOGC) technique for lumped Raman fibre amplifiers. This technique has previously been tested for gain stabilization of erbium-doped fibre amplifiers. We have analyzed, both theoretically and experimentally, the suppression of transient and steady-state surviving channel power excursions in an AOGC lumped Raman fibre amplifier. Theoretical analysis is based on application of a comprehensive large-signal dynamic model of the Raman fibre amplifier. We have confirmed our theoretical results experimentally and found that if sufficient lasing is allowed, the steady-state surviving channel power fluctuations are fully eliminated. Amplitude of the remaining power transients that occur when channels are switched off/on is about 10 times lower than the steady-state power excursion of the unclamped Raman fibre amplifier.

The left figure show theoretically calculated surviving-channel power fluctuations in one of the 16 channels when 8 channels are periodically dropped/added. The right figure depicts the results of experimental verification. Raman fibre amplifier parameters are the same for both the theoretical and experimental verification.

  1. Karásek, M., Menif, M., Bellemare, A.: Remotely pumped hybrid amplifiers for extended bidirectional passive optical networks. Fiber and Integrated Optics 22: 13-24 (2003).
  2. Karásek, M., Kaňka, J., Honzátko, P., Radil, J.: Protection of Surviving Channels in All-Optical Gain‑Clamped Lumped Raman Fibre Amplifier: Modelling and Experimentation. Optics Communications 231: 309-317 (2004)
  3. Karásek, M., Kaňka, J., Honzátko, P., Radil, J.: Channel Addition/Removal Response in All-Optical Gain-Clamped Lumped Raman Fiber Amplifier. IEEE Photonics Technology Letters 16: (March 2004, in print)
  4. Karásek, M., Kaňka, J., Honzátko, P., Radil, J.: All-Optical Gain-Controlled Lumped Raman Fibre Amplifier. 8th Working Conference on Optical Network Design and Modelling, 2.-4. February 2004, Ghent, Belgium, Proceedings (2004, accepted for presentation).