2-STAGE PERTURBATION-THEORY FOR BANDWIDTH-LIMITED AMPLIFICATION OF OPTICAL SOLITONS NEAR THE ZERO-DISPERSION POINT

We show that soliton propagation in transmission lines where bandwidth -limited amplification, nonlinear gain or loss, and a strong third-ord er dispersion are present can be reasonably described in terms of a '' two-stage'' perturbation theory. In contrast to the adiabatic soliton perturbation theory which is known to fail beyond a critical strength of third-order dispersion, a modulation of the soliton phase caused by third-order dispersion is taken into account in this approach.