OBSERVATION OF COLLISION-INDUCED TEMPORARY SOLITON CARRIER FREQUENCY-SHIFTS IN ULTRA-LONG FIBER TRANSMISSION-SYSTEMS

Multiwavelength soliton interaction over 10 000 km in an Er3+-doped fiber amplifier based system is studied in a fiber loop configuration. Collisions that take place over distances significantly longer than the amplification period are found to produce nonpermanent shifts of the soliton carrier frequencies, thus acting as collisions in a lossless medium. The spectral shift is found to be inversely proportional to the wavelength separation and is reduced with increasing pulse width. The effects of these unavoidable collisions will impose a limit on the minimum channel spacing in ultra-long-haul soliton based communication systems.