Propagation of a light pulse in nonlinear tunnel-coupled optical waveguides

Propagation of a short optical pulse in a two-channel fiber waveguide is described by a system of two coupled nonlinear Schrödinger equations. The Anderson variational method is used to reduce this system to a system of ordinary differential equations describing the spatial evolution of the parameters of a pulse. Analytic solutions of these equations are found in two limiting cases and it is shown that the propagation regime changes in some critical power W_c of the incident pulse. For example, when the power exceeds W_c, the radiation is concentrated practically in one channel. These results are in agreement with those obtained earlier by numerical modeling.