RESONANT SPLITTING OF A VECTOR SOLITON IN A PERIODICALLY INHOMOGENEOUS BIREFRINGENT OPTICAL-FIBER

We analyze the dynamics of a two-component (vector) soliton in a model of a birefringent nonlinear optical fiber with a periodic spatial modulation of the birefringence parameter (group velocity difference). Evolution equations for the parameters of the vector soliton are derived by means of a variational technique. Numerical simulations of these equations demonstrate that the critical modulation amplitude necessary for splitting, regarded as a function of the soliton's energy, has a deep minimum very close to the point at which direct resonance takes place between the periodic modulation and an internal eigenmode of the vector soliton in the form of small relative oscillations of the centers of the two components. A shallower minimum, which can be related to another internal eigenmode of the vector soliton, is also found. We further briefly consider the internal vibrations of the vector soliton driven by a constant force, which corresponds to the birefringence growing linearly with propagation distance. The effect predicted has practical relevance to ultrashort (femtosecond) optical solitons, and it can be employed in the design of fiber-optical logic elements.