A Novel Detection Method of Brillouin Backscattered Light in Optical Fiber

This paper introduces a novel Brillouin signal detection method, including its basic principle and its advantages in a distributed fiber temperature and strain sensing system based on Brillouin scattering. The detection method relies on heterodyne detection which does not need an extra reference light, and has many special advantages compared with the interference detection method. Careful and detailed experiments were performed to prove its feasibility, including: basic verification, temperature and strain experiments, all of which used a narrow linewidth source at 1.55 $\mu {\rm m} $ and produced positive and promising results. In the first experiment, a peak frequency shift due to Brillouin scattering of 10.8420 GHz is obtained, consistent with the theoretically predicted Brillouin frequency shift; in the second experiment, the temperature coefficient is obtained as 1.0843 ${\rm MHz}/^{\circ}{\rm C} $, which close to the previously reported value of 1.2 ${\rm MHz}/^{\circ}{\rm C} $; in the third experiment, the strain coefficient is obtained as 0.049 ${\rm MHz}/\mu \varepsilon $, again, in agreement with the previously reported value of 0.0496 ${\rm MHz}/\mu \varepsilon $.