Abstract

Dark solitons in optical fibres have received increased interest because of their potential advantages over bright solitons with respect to soliton interactions and sensitivity to noise in optical long distance transmission lines. Most recently, 10 Gbit/s pseudorandom dark soliton data have been generated and transmitted over 1200 km [1]. We demonstrate here a novel all-optical technique to generate a multigigahertz dark soliton train by using a high resolution filtering of a conventional mode-locked laser source [2]. The amplitude and phase filtering is performed by a specially designed fibre Bragg grating [3] and converts a 17 ps, 6.1 GHz bright pulse train into a 33 ps dark pulse train with an identical repetition rate. A numerical comparison between the temporal shape of the dark pulse train and its spectrum indicates that both the amplitude and the phase filtering are correctly performed i.e. that the dark pulses exhibit an approximate π phase shift across the dark part of the pulse.

© 1996 IEEE