The build-up of stimulated Brillouin scattering excited by pulsed pump radiation in a long optical fibre

We study stimulated Brillouin scattering (SBS) in a long optical fibre with and without feedback under long pulse excitation, when the acoustic field is steady state. It is shown that, when the pump power is higher than the f eedback free SBS threshold, the build-up time is inversely proportional to the pump power and independent of feedback. At lower pump power, for which feedback is required to produce SBS, the build-up time increases inversely with the difference between the pump power and the SBS threshold with feedb ack. The build-up time may be varied from submicroseconds to milliseconds d ependent on the pump power and feedback strength in agreement with our theo retical description. (C) 2000 Published by Elsevier Science B.V.