IDEAL AMPLIFICATION OF AN ULTRASHORT SOLITON IN A DISPERSION-DECREASING FIBER

A scheme for the reshaping of ultrashort solitons in a lossy fiber, ba sed on abrupt increase of the fiber's dispersion just before applicati on of a strong amplification pulse and on further gradual return of th e dispersion to the bulk value, is proposed. The enhanced dispersion c an be matched to the gain so that the amplified solitary wave will alw ays be an exact soliton with no radiation. With the adiabatic invarian t technique, it is demonstrated that the soliton will smoothly evolve down to the bulk value of the dispersion without being disturbed and t hat the scheme is stable against spontaneous chirp generation.