High efficiency in a double-pass Brillouin amplifier with noise suppression

This paper develops a method to suppress noise exiting a Brilliouin amplifier (BA) by taking advantage of the thresholding response of an SBS cell. It shows that returning the pump and the phase conjugate signal, after its noise component has been reduced back into the BA, permits performing an efficient second amplification stage. Double-passing the BA without first performing noise reduction well reduce the efficiency, since the noise which is still present undergoes gain, thus competing with the signal.