Interaction of solitons in tunnel-coupled optical fibers

A pair of weakly interacting optical fibers, which are described by two nonlinear Schrödinger equations with linear coupling terms, is considered in the framework of perturbation theory. It is shown that the interaction of optical solitons in this system is inelastic and that they may form a bound state (bisoliton). The stability and internal oscillations of the bisoliton are also investigated.