Asymptotical solutions of coupled nonlinear Schrödinger equations with perturbations

In this paper Lou's direct perturbation method is applied to the perturbed coupled nonlinear Schrödinger equations to obtain their asymptotical solutions, which include not only the zero-order solutions but also the first-order modifications. Based on the asymptotical solutions, the effects of perturbations on soliton parameters and the collision between two solitons are then discussed in brief. Furthermore, we directly simulate the perturbed coupled nonlinear Schrödinger equations by split-step Fourier method to check the validity of the direct perturbation method. It turns out that our analytical results are well supported by the numerical calculations.