Dual-longitudinal-modes narrow-linewidth fiber Raman amplifier

A fiber Raman amplifier (FRA) with dual-longitudinal-modes narrow-linewidth output is reported. Firstly, the dual-longitudinal-modes seed light with 1.4 GHz frequency spacing and a power proportion of 3∶1 is obtained by a home-made dual-longitudinal-modes narrow-linewidth fiber laser operating at 1 079.7 nm. The linewidth of each longitudinal mode is about 10 MHz. Then, the dual-longitudinal-modes seed light is amplified to a maximal power of 1.07 W with 1 031 nm pump source. The linewidth, frequency spacing and power proportion of the two longitudinal modes of the seed light have been maintained during the amplification.