NUMERICAL STUDY OF THE REDUCTION OF INSTABILITY IN BANDWIDTH-LIMITED AMPLIFIED SOLITON TRANSMISSION

In soliton transmission systems with bandwidth-limited amplifications, solitons tend to be destroyed during long-distance propagation owing to the interaction with linear dispersive waves, which are generated from solitons by the filtering and amplified by the excess gain around the filter center frequency. Recently Kodama et al. [Electron. Lett. 28, 1981 (1992)] suggested that the instability may be suppressed by introducing amplifiers with nonlinear gain, or gain and saturable absorption in combination. We demonstrate numerically the validity of using nonlinear gain to stabilize soliton transmissions where the filters are incorporated to reduce the Gordon-Haus frequency shift.