Abstract

Work on transatlantic communications systems has already shown [1] that the maximum bit-rate/distance product for any system length is always obtained by transmitting well spaced transform limited pulses (solitons), e.g. 20 ps pulses for 10 Gbit/s transmission over 5000 km [2]. In a 40 Gbit/s network similar techniques would allow transmission over 1-2000 km using 3-5 ps pulses [3]. The principal barrier to development of such systems has always been the lack of a suitable pulse transmitter, which must produce high power, transform limited ps pulses at GHz rates, and must also be portable and stable for long periods (years). Recently it has been shown that suitable pulses can be generated by optically amplified semiconductor laser sources [4-6], similar to those used in current lightwave transmission systems. Two techniques have been used; gain switching and filtering [4],which is simple to implement but produces substantial pulse to pulse jitter, and mode-locking [5,6], which produces better pulses but is subject to stability problems. In this paper we show for the first time that the mechanical problems associated with external cavity mode-locked lasers can be overcome, without compromising on output pulse quality, by building a packaged cavity, and that the important operating parameters are amenable to external control for long term stability.

© 1991 Optical Society of America