A nonlinear lightguide as a transmission medium of ultrashort chirped hyperbolic secant shape and rectangular pulses

The propagation of ultrashort chirped hyperbolic secant shape and rectangular pulses in a nonlinear lossless fiber is considered. Nonlinear Schrodinger equation is solved numerically for complex initial conditions using the split-step Fourier and the beam propagation methods. It is demonstrated that a hyperbolic secant shape pulse is less sensitive to destructive influence of the initial chirp than a rectangular pulse.