Effect of Stimulated Brillouin Scattering on Raman Amplification in Single Mode Optical Fibers.

This work is an experimental study of the effect of stimulated Brillouin scattering on Raman amplification in a single mode optical fiber. A theoretical analysis of the stimulated Brillouin power distribution in the fiber shows that there is significant buildup of backward scattered Brillouin power in the first small fraction of the fiber. Calculated amplified spontaneous Raman gain for the depleted pump indicates that the Raman gain would be saturated even if the Brillouin gain coefficient were reduced. Amplified spontaneous emission and signal gain due to Raman amplification in a fiber were measured for varying levels of stimulated Brillouin scattering. These measurements indeed show the saturation at low gain for the Raman amplifier due to pump depletion by stimulated Brillouin Scattering. This pump depletion also leads to Raman gain fluctuations arising from mode partitioning in a multimode pump laser.