Abstract

For distributed temperature sensing based on Brillouin scattering, narrow linewidth pulsed sources are required to spectrally resolve the Rayleigh and Brillouin backscattered radiation. The temperature is determined by the relative intensity of the Rayleigh and Brillouin backscattered light i.e the Landau-Placzek ratio^[1]. Typically the backscattered Brillouin is separated from the Rayleigh by about 10 GHz A Q-switched fibre laser using a narrowband in-fibre Bragg grating as an output coupler ensures the Q-switched laser operates with a narrow linewidth, whilst the Q-switched operation produces the high power pulses necessary to produce a stong back-scattered Brillouin signal. Figure 1 shows the optical arrangement used for the Q-switched laser.

© 1996 IEEE