Chirp reduction for arbitrary pulses by amplified chirped-pulse self-phasemodulation in dispersion-shifted fiber

Negatively chirped pulses, with different chirp value or temporal profile, can be easily generated by direct modulation of semiconductor lasers. In th is paper, we describe a method of chirp reduction for such pulses by using chirped-pulse self-phase modulation (SPM) in dispersion-shifted fiber (DSF) . By using an optical amplifier and adjusting the peak pulse power, positiv e chirp induced from the intensity-dependent SPM in DSF can compensate an a rbitrary negative chirp in the pulse without changing the pulsewidth. We pr esent for the first time the basic theory of chirped-pulse SPM. Chirp reduc tion of a 2.6-GHz train of gain-switched pulses was demonstrated experiment ally, in agreement with the theory. (C) 1999 Published by Elsevier Science B.V. All rights reserved.