Dark soliton solutions for the coupled variable-coefficient fourth-order nonlinear Schrödinger equations in the inhomogeneous optical fiber

Abstract

In this paper, we discuss the bright–dark and dark–dark soliton solutions for the coupled variable-coefficient fourth-order nonlinear Schrödinger equations, which describe the nonlinear waves propagating simultaneously in an inhomogeneous optical fiber. The bilinear forms with auxiliary functions are derived through the Hirota method. Based on the bilinear forms, we construct the bright–dark and dark–dark soliton solutions. The effects of variable coefficients on structures of the bright–dark and dark–dark solitons are analyzed. The propagation of bright–dark soliton and elastic interactions between dark–dark multi-solitons are illustrated graphically.