INTERNAL DYNAMICS OF A VECTOR SOLITON IN A NONLINEAR-OPTICAL FIBER

We analyze the dynamics of a vector soliton governed by a nearly integ rable system of coupled nonlinear Schrodinger equations. Inserting a G aussian ansatz into the Lagrangian density, we derive a system of ordi nary differential equations for the evolution of the ansatz parameters . We find a continuous family of stationary solutions to these equatio ns which can be interpreted as vector solitons with an arbitrary polar ization. Examining small internal vibrations of the vector soliton, we find three eigenmodes, of which only two were previously known. The a dditional internal oscillation eigenmode gives rise to antisymmetric o scillations of the symmetric soliton (45-degrees polarization). We als o find the small-vibration eigenmodes for arbitrary polarization, thou gh in an implicit form. Additionally, we find a threshold value of the relative velocity of the two polarizations that leads to splitting of the vector soliton for arbitrary polarization.