Bilinear forms, modulational instability and dark solitons for a fifth-order variable-coefficient nonlinear Schrödinger equation in an inhomogeneous optical fiber

Abstract

In this paper, a fifth-order variable-coefficient nonlinear Schrödinger equation in an inhomogeneous optical fiber is investigated. Bilinear forms, which are different from those previously reported, are obtained under certain vraible-coefficient constraints. Modulational instability is shown to be related to the group velocity dispersion, Kerr nonlinearity and fifth-order dispersion. Dark soliton solutions are presented and discussed: Soliton velocity is related to the Kerr nonlinearity and fifth-order dispersion, while soliton amplitude is independent of them. Interactions between the dark two solitons are elastic, possibly the overtaking or head-on interactions. Soliton stability is also discussed via the numerical simulation, and the latter is verified through the independence verification.