A theoretical comparison of spontaneous Raman and Brillouin based fibre optic distributed temperature sensors

Present day commercially available fibre optic distributed temperature sensors exploit the temperature dependence of spontaneous Raman scattering. Spontaneous Brillouin scattering is also temperature dependent and provides a signal which is an order of magnitude greater. Advances in narrow bandwidth pulsed laser technology and low loss all fibre filters allow the Brillouin signal to be separated from the Rayleigh signal. Theoretical analysis now demonstrates that distributed temperature sensing based on Brillouin scattering offers considerably increased range beyond the theoretical limit of the spontaneous Raman based sensor