Optimal use of the Raman effect for transmission of narrow solitons through sliding-frequency filters

Abstract

Sliding-frequency filters (SFFs) are currently the most standard and proven means of suppressing the degrading effect of the Gordon-Haus jitter on data transmission in soliton-based optical communication systems. In the current state of technology, solitons are usually broad enough (10-20 ps) so that the Raman effect is insignificant; but for shorter solitons (which can support a greater bit-rate), the Raman effect, scaling as (width)-4, more strongly than the non-Raman effects, becomes significant. The Raman effect shifts (downward) a soliton’s frequency, one of the SFF’s essential tasks. We therefore conjecture that if the SFF’s frequency ramp and the Raman frequency-sliding rate are properly matched, the frequency-sliding of narrow solitons can be generated by the Raman effect, and the SFF, liberated from its task of generating the solitons’ frequency-sliding, may be chosen to minimize unnecessary SFF-associated losses, minimizing the (detrimental) compensatory gain and degradation of the signal.