Abstract

Recently several groups have reported error free soliton transmission over more than 9,000 km at Gbit/s rates.^1,2 When solitons are generated by gain-switched¹ lasers, the pulses are severely chirped and a narrowband optical filter must be used. It has been observed a large pulse spreading for distances greater than a few thousand kilometers when using a DFB laser, bias current (C_b) above threshold and repetition rate of 2.4 Gbit/s.³ We have recently shown that this pulse spreading is due to the pulse-to- pulse frequency jitter originated in the laser diode.⁴ In this work we numerically obtain that when the laser is biased slightly below threshold pulse spreading is strongly reduced for any frequency of modulation in the GHz range, and both periodic (PM) and pseudorandom word (PRWM) modulation regimes.

© 1994 Optical Society of America