Distributed Optical Fiber Vibration Sensing Based on Semiconductor Lasers With Optical Injection

A bidirectional distributed optical fiber vibration sensing (DOFVS) system based on the optical injection effect of semiconductor lasers is proposed. The system consists of double unidirectional DOFVS sub-systems based on a semiconductor laser with optical injection. The two sub-systems share a master laser and a bidirectional injection channel that serves as the sensing fiber. The injection locking states are employed as the operation states of the DOFVS system. The phase modulation caused by an external vibration is converted into intensity modulation through the nonlinear effect of the semiconductor lasers. The output signals of the system in two opposite directions exhibit highly similar waveform changes caused by the same external vibration. The time shifting deviation method is used to estimate the time difference between the waveform changes of the two signals and determine the position of the vibration. The feasibility of the system is verified through simulation and experiment. The average location error of less than 9 m on the 4288.7 m sensing fiber is obtained experimentally. The system works stably with simple structure and high utilization of optical fiber, without limitation on duration or bandwidth of vibration signals. Its detection speed is fast and location accuracy is high.