Effect of coherence on all-optical signal amplification by supercontinuum generation

We present a detailed study of all-optical signal amplification that exploits the extreme sensitivity of supercontinuum generation to input power fluctuations. As useful signal amplification relies on determinism and correlation between input and output signals, the question naturally arises whether such conditions can be maintained in the presence of modulation instability, which is known to strongly affect the coherence of supercontinuum pulse trains. In order to address this question, the effect of supercontinuum coherence on the amplification of a modulation is investigated when injecting weakly modulated 200-fs input pulses into a photonic crystal fiber. Our study, which is performed for multiple spectral channels across the full bandwidth of the supercontinuum, clearly shows that even in the case of partial coherence, the amplification mechanism based on soliton-dispersive wave coupling can be maintained, allowing for the amplification of weakly modulated signals by factors in excess of 40 dB in the normal dispersion regime.