Optical quasi-soliton solutions for higher-order nonlinear Schrödinger equation with variable coefficients

Optical quasi-soliton solutions for higher-order nonlinear Schrödinger equation (HNLS) with variable coefficients are considered. Based on the extended tanh-function method, we successfully obtained bright and dark quasi-soliton solutions under certain parametric conditions. We conclude that the parameter k(z) is unnecessary to be zero compared with [R. Yang et al., Opt. Commun. 242 (2004) 285]. Furthermore, we choose appropriate optical fiber parameters D2(z) and D3(z) to control the velocity of quasi-soliton and time shift, and discuss the evolution behavior of the special quasi-soliton. For D3(z) = α(z) = f(z) = 0, that is to say, under the absence of the higher order terms, we give same results as early reported in [R.Y. Hao, L. Li, Z.H. Li, W.R. Xue, G.S. Zhou, Opt. Commun. 236 (2004) 79]. As discussed examples, we also analyze three optical systems with real physical significance and obtain results which can be recovered in earlier papers.