Abstract

Since Mollenauer and Smith experimentally evidenced the stable propagation of solitons in fibers over 6000 km, soliton-based communications become even more attractive. Although solitons, produced by a soliton laser, are used as inputs in the aforementioned experiment, nonsoliton pulses can actually be used as input signal carriers in soliton-based communications. It has been shown that, if the input energy is high enough, during the evolution of a nonsoliton pulse, a solitonlike central part is formed and the remaining energy is separated from the central part to form dispersive tails. We report the research results of some problems in using nonsoliton inputs for soliton-based communications. First, it is discovered that besides the slow oscillations of soliton shape during evolution, fast oscillations are produced when the generated dispersive tails of the neighboring bits extend into the soliton part. Second, we found that the bit-bit interaction becomes stronger due to the existence of dispersive tails. For example, the evolving solitons in two consecutive bits will merge earlier than two ideal solitons. This implies a more restrictive limitation on bit rate when nonsoliton pulses are used as inputs. The third problem is related to the cross-phase modulation between two channels. It is discovered that pulses become asymmetric in cross-phase modulation due to the afore-mentioned fast oscillations.

© 1989 Optical Society of America