Characterization of Brillouin frequency shift in Brillouin Optical Time Domain Analysis (BOTDA)

In this paper, we have characterised Brillouin frequency shift (BFS) in single mode silica fibre. In particular, BFS was characterised in conventional Brillouin Optical Time Domain Analysis (BOTDA) at operating wavelength of 1550 nm by a pump-probe technique. In addition, we also presented Brillouin gain and Brillouin loss mechanism in BOTDA sensing system. The simulation results shows, BFS have strong linear relationship with acoustic velocity and applied strain along the sensing fibre. A frequency shift of 60 MHz was obtained for each 0.1% strain (1000 μ-strain) on fibre. From the measurement results, it was evident that the each μ-strain on the fibre the frequency shift was found as 0.06 MHz. Therefore, BOTDA sensing system based on BFS is a promoting technique for structural health monitoring.