Spectral broadening in Raman fiber amplifier pumped by partially coherent wave

In this paper, spectral broadening of the amplified signal in Raman fiber amplifiers is reported when a broadband continuous wave pump is used in a copropagating configuration. A Raman laser operating at 1455 nm is used as a pump. A wavelength division multiplexer (WDM) combines both waves for interaction in a 6 km long single dispersion shifted mode fiber. A scanning Fabry-Perot interferometer with a free spectral range of 15 GHz and a resolution (FWHM) of 100 MHz is used to analyze the signal spectrum. In addition, the numerical integration of the nonlinear Schrodinger equations was performed considering a CW signal and taking into account the partial coherence of the pump wave. The simulation result gives a good agreement with the experimental data confirming the mechanism of the spectrum broadening.