Propagation of nonlinear pulses in chirped fiber gratings

The propagation of nonlinear optical pulses in chirped fiber gratings is studied. The dynamics is analyzed on the basis of the inhomogeneous nonlinear Schrodinger equation. By using perturbation theory we demonstrate that the inhomogeneity affects the amplitude and the width, as well as the phase and the velocity of the soliton. The dynamics of a multisoliton pulse (breather) in chirped gratings is also discussed. It is shown that the velocity variation of individual solitons leads to the breaking of a bound multisoliton state. This process manifests itself as the pulse splitting that is experimentally observed by other authors. Numerical simulations of the pulse dynamics agree well with analytical results for wide range of parameters.