The scale of China’s infrastructure has been ranked first in the world.Natural disasters,human factors,and structural defects can lead to damage and incalculable loss of life and property.The accident of infrastructure is usually manifested as vibration.By monitoring the vibration event,it can timely discover the hidden dangers and take corresponding measures to avoid the accidents.Distributed optical fiber vibration sensing technology based on phase-sensitive optical time domain reflectometry(Φ-OTDR)can be widely used in the field of health monitoring of large infrastructure,owing to the advantages of distributed monitoring,fast response and high detection sensitivity.However,due to the complexity of the field environment,its commercial sensing equipment is difficult to meet the application needs.The amplitude and phase of the RBS are random distribution,there will be a coherent fading effect during the superposition of RBS,so that there is a dead zone in the detection.Due to the influence of environment,the polarization state changes frequently and polarization-related noise is introduced to the sensing system.The spectrum of background noise in the field environment is broadband,and the length of vibration events is unpredictable.Excessive spatial resolution will lead to the decline of signal-to-noise ratio and affect the overall performance of the system.Becides,there exists a tradeoff between sensing distance and frequency response,leading to the long sensing distance and high frequency vibration can not be realized in conventionalΦ-OTDR at the same time.In this paper,the research is mainly focusing on Φ-OTDR sensing principle,detection structure and performance parameters.A Φ-OTDR acoustic field sensing system based on self-heterodyne detection and ultra-weak reflection Bragg grating(UWFBG)array was demonstrated.By optimizing the system structure,the Φ-OTDR system could fully restore the vibration with high spatial resolution,high reconstruction fidelity,long sensing distance,and dead-zone free at the same time.A method for performance optimization of Φ-OTDR acoustic field sensing system based on multi-spatial resolution(MSR)analysis was proposed.By using this proposed MSR sensing system,the SR and the length of vibration region can be matched as much as possible.Therefore,the performance optimization of Φ-OTDR sensing system can be obtained without reducing the detection frequency range.A broadband vibration Φ-OTDR sensing system based on the distributed feedback interferometer(DFI)was proposed and demonstrated,which can extend the frequency response range of the Φ-OTDR system.The performance of distributed optical fiber sensing device based on Φ-OTDR has been improved,which is more suitable for applications.Related sensing device developed by research group has been applied in applications such as seismic wave detection and high-speed rail online monitoring,which obtained good results.This will play an important role in promoting Φ-OTDR in the application of health monitoring. |