Transient response in high-resolution Brillouin-based distributed sensing using probe pulses shorter than the acoustic relaxation time

We perform numerical simulations on a model describing a Brillouin-based te mperature and strain sensor, testing its response when it is probed with re latively short pulses. Experimental results were recently published [e.g., Opt. Lett. 24, 510 (1999)] that showed a broadening of the Brillouin loss c urve when the probe pulse duration is reduced, followed by a sudden and rat her surprising reduction of the linewidth when the pulse duration gets shor ter than the acoustic relaxation time. Our study reveals the processes resp onsible for this behavior. We give a clear physical insight into the proble m, allowing us to define the best experimental conditions required for one to take the advantage of this effect. (C) 2000 Optical Society of America. OCIS code: 060.2370, 190.5890, 290.5900.