Effectiveness of gain control in EDFAs against traffic with different levels of bursty behaviour

Previous publications have addressed the impact of bursty, self-similar tra ffic on erbium-doped fibre amplifiers (EDFA). Several gain control techniqu es have been suggested to combat the gain fluctuations of EDFA with this ty pe of traffic. The effectiveness of two such methods are investigated, name ly highly inverted amplifiers and all-optical gain clamping, while varying the parameters characterising the burstiness of the sources. While previous publications have focused on the effect of the average load or activity fa ctor, the paper further investigate the dependence on the relative variabil ity of the packet burst lengths (ON times), and lengths of the interburst i dle times (OFF times). Both gain control methods reduce the output power an d signal-to-noise ratio excursions with respect to a standard amplifier cha in. The authors find that, for an eight channel WDM system and a cascade of six EDFAs, all-optical gain clamping can reduce the variations by a factor of five, provided adequate power is present in the clamping laser, while h ighly inverted amplifiers have variations reduced by a factor of two. The a uthors find that, in a clamped chain, the source activity factor does not u niquely determine the required level of lasing power. The authors also dedu ce that information on the relative variability of ON and OFF times is esse ntial.