Dark optical solitons with finite-width background pulses

Abstract

Using numerical solutions of the nonlinear Schrödinger equation, we show that for positive group-velocity dispersion, optical dark pulses superimposed upon background pulses only ~10× wider can exhibit stable soliton propagation in single-mode fibers. During propagation the background pulse spreads (which reduces its intensity) and develops a frequency chirp. Nevertheless, as the background pulse evolves the dark pulse adiabatically maintains its soliton characteristics. These numerical results are in excellent agreement with recent experimental investigations of dark-pulse propagation in fibers.