Femtosecond soliton interactions m a distributed erbium-doped fiber amplifier

Nonlinear interactions between femtosecond solitons have been investigated in a distributed erbium-doped fiber amplifier (DEDFA). Fluctuations in soliton amplitude cause significant changes in femtosecond soliton-soliton interactions through the soliton self-frequency shift (SSFS). The noninstantaneous response of the medium causes amplitude asymmetry between two adjacent solitons and also modifies the soliton interaction. It is shown that a small subpulse, which is coherently added to or subtracted from a soliton pulse, greatly modifies the soliton-soliton interaction in a DEDFA. This effect is significantly enhanced by the optical gain. It is also shown that when the input femtosecond soliton pair is in phase, the SSFS is greatly accelerated through soliton interactions