Vector–soliton bound states for the coupled mixed derivative nonlinear Schrödinger equations in optical fibers

In this paper, the vector–soliton bound states (VSBSs) are investigated for the coupled mixed derivative nonlinear Schrödinger equations, which can describe the pulse propagation in the femtosecond regime of birefringent optical fibers. Symmetric and asymmetric VSBSs with the periodic collisions are obtained and analyzed. The intensity profile and collision period of the bound state are related to the ratio of the real parts of two wavenumbers. The separation factors are introduced in the solutions to linearly adjust the soliton separations. Amplitude-changing collisions between the VSBS and vector bright solitons are also obtained. Via the split-step Fourier method, stability analysis shows that the VSBSs can resist the finite initial perturbations. In addition, the derivative cubic nonlinearity and cubic nonlinearity terms are found to both have no influence on the types of VSBSs, but leads to one-sided compression, center shifts and amplitude decrease of the VSBSs. Energy-exchanging phenomena during the amplitude-changing collisions are not affected, either.

► Symmetric and asymmetric VSBSs with periodic collisions are obtained.
► Soliton separation can be modified directly through the separation factors.
► Amplitude-changing collisions exist between the VSBS and vector soliton.
► VSBSs can almost resist the finite initial perturbations.
► Comparisons between the VSBSs for the CNLS and CMDNLS equations are given.