RESONANT SHAPE OSCILLATIONS AND DECAY OF A SOLITON IN A PERIODICALLY INHOMOGENEOUS NONLINEAR-OPTICAL FIBER

The propagation of a soliton in a nonlinear optical fiber with a perio dically modulated but sign-preserving dispersion coefficient is analyz ed by means of the variational approximation. The dynamics are reduced to a second-order evolution equation for the width of the soliton tha t oscillates in an effective potential well in the presence of a perio dic forcing induced by the imhomogeneity. This equation of motion is c onsidered analytically and numerically. Resonances between the oscilla tions in the potential well and the external forcing are analyzed in d etail. It is demonstrated that regular forced oscillations take place only at very small values of the amplitude of the inhomogeneity; the o scillations become chaotic as the inhomogeneity becomes stronger and, when the dimensionless amplitude attains a threshold value which is ty pically less than 1/4 the soliton is completely destroyed by the perio dic inhomogeneity.