Automatic real-time control for gain-flattened fiber Raman amplifiers

An automatic control algorithm for flattening the gain of a fiber Raman amplifier is derived from the Raman scattering equations. A pseudo-inverse gain matrix is introduced to adjust the powers of the pump lasers. The algorithm is simple, fast, effective, robust and insensitive to the length and type of the fiber. It is demonstrated experimentally that the gain flattening for Raman amplifiers comprising various types and lengths of fiber and with different target gains can be achieved automatically with this algorithm. The algorithm converges for both small and large input signal. Flattened Raman gain with a fluctuation less than 0.40 dB over a 50-nm bandwidth for a 50-km SMF or less than 0.20 dB over a 40-nm bandwidth for a 6.6-km dispersion compensated fiber is realized in the experiment. (C) 2004 Elsevier B.V. All rights reserved.