Suppression of stimulated Brillouin scattering effect in fiber amplifiers

A multi-tone narrow-linewidth fiber amplifier is demonstrated. In this kind of amplifier the seed laser is attained by combining several single frequency seed lasers which all have nearly the same wavelength (wavelength separation less than 1 nm) and with frequency difference larger than twice the Brillouin shift. An integrated theoretical model of this kind of amplifier is set up. Relationship between stimulated Brillouin scattering(SBS) and the number of the seeds is analyzed using this model. Two-tone and three-tone amplifiers are set up to study SBS threshold output power experimentally. The experimental results are in good agreement with theoretical results, revealing rationality of the theoretical model. Two-tone and three-tone amplifications can suppress SBS effectively and enhance output powers of narrow-linewidth fiber amplifiers greatly.