Application of Stimulated Brillouin Scattering in Distributed-Temperature Sensors Using Single-Mode Optical Fibers

This research investigates one of the stimulated Brillouin scattering applications related to distributed-temperature sensors that utilize common single-mode optical fibers. The aim is to find a relation between the Brillouin frequency shift (BFS) and temperature up to 15000C in these distributed-temperature sensors. At first, a linear approximation of the acoustic wave velocity and a reported polynomial of the refractive index with temperature are employed to calculate BFS. A comparison of the obtained BFS with two independent sets of recent experimental data shows that the linear relation between acoustic wave velocity and temperature, which is generally considered valid, is not valid, especially at high temperatures. Then, using a curve-fitting method based on another reported experimental data set, different-order polynomials of degrees up to six are considered for the acoustic wave velocity with temperature. The results show that the proposed second and third-order polynomials of the acoustic wave velocity can be used to calculate BFSs that align more closely with experimental data, even at elevated temperatures.