Approximate model of soliton dynamics in all-optical couplers

Using a variational method, we have developed an approximate model of the dynamics of soliton coupling described by coupled nonlinear Schr\"odinger equations. The results are analytical and can be recast into a suggestive particlelike description providing a physical insight into the problem. The particular case of the nonlinear coherent coupler is emphasized, and an estimate of the soliton switching peak power is obtained. A symmetry-breaking instability is also described, in a simple way, with the potential-well picture.