Stable cw backward Raman amplification in optical fibers by stimulated Brillouin scattering suppression.

A backward pumping scheme with highly repetitive short pump pulses is described for cw Raman amplification of signal light in optical fibers. This pumping scheme makes possible stable and high-gain cw Raman amplification due to the efficient suppression of stimulated Brillouin scattering, which not only limits the gain but also deteriorates the gain stability of such amplification. Stable cw backward Raman amplification of 1.4-μm laser diode light signals has been achieved, for the first time, with gains as high as 14 dB in a 5.5-μm core diam and 3.5-km long single-mode fiber, pumped with a 1.32-μm mode-locked Nd:YAG laser.