Research on anti-interference characteristics of distributed fiber optic vibration sensing system based on OFDR

An improved differential cross-multiplication algorithm and cross-correlation algorithm are proposed for vibration demodulation and location, and its performance in engineering structure health monitoring under strain and temperature interference is deeply studied. Experimental results demonstrate that the system can measure vibration frequency ranging from 10 Hz to 20 kHz while effectively restoring signal time-domain waveforms, achieving a positioning accuracy of 6.25 cm. Based on the application of sensitive fibers embedded within material interiors or adhered to surfaces for structural health monitoring scenarios, anti-interference test experiments were conducted. Aiming at the spectrum broadening phenomenon of vibration signal demodulation under interference, the dynamic positioning strong reflection point position optimization algorithm is adopted. The results show that the spectral peak broadening is basically consistent in the strain range below 2000 με and the temperature range below 200 °C, and the anti-interference ability of the system is improved. In addition, the detection ability of the system in complex signal environment is further verified by the superposition test of manual knocking vibration signal and PZT driving signal.