DARK SOLITONS ON BACKGROUNDS OF FINITE EXTENT

Adiabatic modification of a dark soliton due to dispersion- (or diffraction-)induced spreading of a finite-width background is investigated. It is proved analytically that a frequency chirp of the background of finite extent does not affect the soliton motion, as was earlier observed in numerical simulations and experimental investigations of dark-pulse propagation in optical fibers, It is also shown that the background-induced dynamics of a dark pulse may be treated as a combined effect of the background decay and ''internal'' soliton dynamics, these two effects may almost compensate each other recovering properties of perfect dark solitons on infinite backgrounds.