Channel addition-removal response in all-optical gain-clamped lumped Raman fiber amplifier

Application of all-optical gain-clamped (AOGC) lumped Raman fiber amplifier (RFA) for protection of surviving channels in multiwavelength networks is investigated experimentally and theoretically. Channel addition-removal was simulated by transmitting signals of two lasers through a counterdirectionally pumped RFA consisting of 16 km of dispersion compensating fiber. Light of one of the lasers was square-wave modulated at 500 Hz; power fluctuations of the other laser caused by cross-gain modulation of the RFA were monitored at the output of the amplifier with a digital oscilloscope. An all-optical feedback loop was implemented in the form of a ring laser. Theoretical analysis of the AOGC lumped RFA is based on numerical solution of coupled propagation equations for forward and backward-propagating pumps, signals, and spectral components of amplified spontaneous emission powers.