Online long-distance monitoring of subway vibration reduction effect using ultra-weak fiber Bragg grating arrays

Monitoring the subway vibration reduction effect is vital since subway train-induced vibration brings great damage and distress to the buildings and residents along the metro line. To deal with the problems encountered in traditional electrical monitoring methods, such as severe electromagnetic interference and short monitoring distance, we propose an online long-distance vibration monitoring method based on ultra-weak fiber Bragg grating vibration sensing arrays. First, two parallel fiber optic cables are laid separately on the metro line's track bed and tunnel wall for the real-time acquisition of the dynamic response signals of passing trains. Next, the time–frequency and correlation signal characteristics of specific measurement points are extracted and analyzed to show the single-point performance of the sensing arrays. Finally, the subway vibration reduction effect of the entire monitoring area in the metro line is calculated to verify the feasibility of the proposed method.