Soliton propagation in long fibers with periodically compensated loss.

With computer simulation, we study soliton propagation in an all optical, long distance communications system where fiber loss is periodically compensated by Raman gain. We find that distortion of the transmitted pulses from true solitons shows a peak near z(0) = L/8, where L and z(0) are the amplification and soliton periods, respectively. We also describe optimal system design based on the exceptional pulse stability and low soliton powers obtained in the region z(0) >> L/8. Typical amplification periods are in the range 30 to 50 km, pump powers are less than 100 mW, and for bit rates in the 10 GHz range, time average signal powers are at most a few mW.