Fibre Raman amplifier pumped by continuous-spectrum radiation

The results of numerical calculations of a fibre Raman amplifier pumped by continuous-spectrum radiation are presented. It is shown that the Raman gain flatness better than 0.1 dB can be achieved in the spectral region between 1528 and 1599 nm at the average gain of 7.7 dB, and the gain flatness of 0.042 dB in the case of the zero average small-signal gain in a 25-km SMF-28 fibre pumped by the 1-W and 364-mW backward radiation, respectively. Different variants of the approximation of the found optimal pump spectrum by a combination of four discrete radiation sources with broadened spectral lines are studied.