Spectral and RIN properties of a single-frequency Raman fiber amplifier co-pumped by ASE source.

Spectral and relative intensity noise (RIN) characteristics of a single-frequency Raman fiber amplifier co-pumped by amplified spontaneous emission (ASE) sources are investigated experimentally. Due to the relatively lower intensity noise of ASE sources compared to usual fiber laser pumps, the full width at half maximum (FWHM) linewidth of the signal laser increases negligibly. But there is significant increase in RIN and spectral wings due to the noise transfer at high frequency from the ASE source during the Raman amplification. The deterioration can be suppressed to some extent with ASE of broader linewidth, which has lower intensity noise.