High Performance Interferometric Distributed Optical Fiber Vibration Sensor

The interferometric distributed optical fiber sensor has the advantages of good insulation,strong ability to resist electromagnetic interference,light weight and high sensitivity,but it also has some problems,such as low positioning accuracy,can not be located at the same time,easily affected by environmental factors and so on.In order to solve these problems,the research on interferometric distributed optical fiber sensor is carried out in this paper.The main contents are as follows:1 The Mach-Zehnder/Sagnac interference system is designed,and the location principle is deduced.To realize its location,the information of the disturbance signal must be demodulated and the frequency spectrum of the disturbance signal is obtained.The most basic method of demodulation phase is the 3X3 coupler method and the PGC demodulation method.The principle of demodulating the phase of 3X3 coupler is deduced mathematically,and the correctness of the demodulation algorithm is verified by simulation.The theory of PGC demodulation algorithm is derived.The simulation results show that the amplitude of the carrier modulation signal is 2.27 and the effect is best,and the PGC demodulation method can be used to demodulate the frequency of 500 Hz to 8000 Hz.The rate of.In the experimental system,PGC demodulation algorithm is used to demodulate phase.2 Based on the Mach-Zehnder/Sagnac interference theory model,the experiment of demodulating the frequency of the disturbance signal in the Mach-Zehnder/Sagnac interference system is carried out.In the experiment,the disturbance signal is used by PZT.The frequency of the disturbance signal is set in the experiment process to be 500 Hz,and the experiment is completed,and each time the 500 Hz repetition experiment is added to the frequency of the disturbance signal.Reach 8000 Hz.The maximum absolute error of experiment is 59 Hz,and the minimum absolute error is 2Hz.The maximum relative error is 3.4%,and the minimum relative error is 1%.3 Based on the Mach-Zehnder/Sagnac interference theory model,the experiment of disturbing event location is carried out.In the experiment,taking into account the limitation of the experimental conditions,the leakage of natural gas is simulated with football outgassing,and the vibration produced in the process of releasing the gas is used as the disturbance source.Different locations were selected for experiments,and the results obtained were compared with the results of high-accuracy OTDR positioning.In the process of seeking zero point frequency,we use wavelet transform to de noise the demodulated frequency signal,so that the location of zero frequency is clearer.The maximum error of experiment is 131 m,the minimum error is 4m,and the average error is no more than 65 m.4 Based on the theoretical model of BP neural network,a BP neural network algorithm is designed.The principal component analysis method is applied to the disturbance events,and the eigenvectors of the disturbance events are extracted.Finally,a set of algorithm is applied to test the sample events.The average correct rate of disturbance events is not less than 70%.