Abstract

All-optical switching in a nonlinear directional coupler and the evolution of the state of polarization in a nonlinear biréfringent fiber represent two important practical problems of propagation in a two-mode, nonlinear dispersive system. Both cases are described by a nonintegrable system of coupled nonlinear Schrödinger equations. On the basis of numerical simulations,¹ it has already been shown that solitons present important advantages over differently shaped pulses. To improve our physical insight into the dynamics resulting from the complex interplay between nonlinearity (self- and cross-phase modulation), dispersion, and linear coupling, we have developed an approximate all-analytical model of soliton interaction. An extension of a variational method² has been used, and the results can be recast in a suggestive potential-well picture. Besides improved estimates of optical switching powers, a symmetry-breaking instability can easily be anticipated. A detailed comparison with numerical simulations, showing a good overall agreement between exact and approximate results, will be presented.

© 1990 Optical Society of America