The study on the novel distributed vibration sensing system based on the adjacent FBGs reflected lights interference

Due to the different polarization states of the reflected light on the two arms of conventional Michelson interferometer, polarization fading of the interferometric signal occurs when environmental perturbations and noise are existing. To solve this problem, in this paper, we design a novel distributed FBG array vibration sensing system based on the interference caused by the reflected signals of the adjacent FBGs. By controlling the pulse width of the input pulse, The reflected light of the adjacent FBGs can interfere on the 3*3 coupler, and we can judge the outside invasion by analyzing the characteristics of the interference signal. The system can demodulate the driving signal with the frequency range of 10 Hz-50 Hz. Comparing with conventional vibration acceleration deteceing methods, the proposed system has the higher sensitivity, wider bandwidth, less response time and better spatial resolution. Meanwhile, the proposed system has sufficient sensing areas which can serve as the high-capacity interferometric seismic detection system.