'Two-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-order 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.