Observation of collision induced temporary soliton carrier frequency shifts in ultra-long fiber transmission systems

Multiwavelength soliton interaction over 10000 km in an Er/sup 3+/-doped fiber amplifier based system is studied in a fiber loop configuration. Collisions that takes place over distances significantly longer than 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.<
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