Pulse Coding in Distributed Optical Fiber Vibration Sensor: A Review

Distributed optical fiber vibration sensor (DOFVS) is suitable for remote monitoring of vibration signals generated by external perturbations. In order to improve the sensing performance, various pulse coding techniques are applied in DOFVS, which have attracted an increasing amount of research attention. In this paper, recent advances of pulse coding methods used in DOFVS are reviewed, from pulse compression, including linear frequency modulation (LFM) and nonlinear frequency modulation (NLFM), pulse coding modulation based on the linear combination and correlation operation, such as Simplex code, Golay code and random code, as well as pulse sequence modulation (PSM), such as phase-shift pulses, differential frequency pulses, etc. Characteristics, working principles and the latest research results of pulse coding methods are discussed. Furthermore, some application progresses of pulse coding for performance enhancement in DOFVS are also introduced. By combining these technologies, the sensing performance could be improved in aspects of sensing distance, spatial resolution (SR), and frequency response, which show considerable potential applications in perimeter security, oil and gas monitoring, pipeline leakage, and structural health monitoring.