Passive reshaping of ultrashort pulses in optical fibers

The passive nonlinear reshaping in normally dispersive optical fibers in the steady-state regime is studied numerically. It is found that normal dispersion and self-phase modulation are able to provide pulse reshaping towards a parabolic pulse profile at the distances exceeding the optical wave breaking length. By matching properly initial pulse parameters and fiber parameters it is possible to change the pulse shape in the steady-state regime. We have found conditions for producing of parabolic pulses from initial secant or Gaussian pulses. The influence of initial pulse shape, initial chirp, third-order dispersion and loss on the parabolic pulse formation is studied consistently, and estimation of practical conditions which are needed for parabolic pulses formation in a passive fiber is given.