Raman amplification using incoherent pump sources

In recent years, optical fiber Raman amplifiers (FRA) have been widely investigated. FRAs use the transmission fiber itself as the gain medium, creating a lossless communication link and reducing the overall noise figure. The later and other promising characteristics put them among the most important technologies in lightwave systems. In Raman amplified systems, the signal amplification is based on stimulated Raman scattering, where the power peak of gain is shifted by approximately 13.2 THz with respect to the pump frequency. The possibility of combining many pumps at different wavelengths, allows the induction of a flat gain in an ultra wide bandwidth. When compared with coherent pumping, the incoherent pumping amplification improves the gain flatness over a broadband. Also due to the random phase of incoherent pumps, the amplification is polarization insensitive. In this paper we analyse the Raman amplification based on incoherent pumps and compare, experimentally and theoretically, this solution with the coherent pumping choice.