A Method on Vibration Positioning of Φ-OTDR System Based on Compressed Sensing

To improve the accuracy of vibration location information of the Φ-OTDR system, a method of optical fiber sensing signal processing based on Compressed Sensing (CS) is proposed in this paper. First, a sensing matrix is constructed by sparse array and observation array, and the mathematical modeling of CS is established. Then the reconstruction algorithm is designed to complete the accurate reconstruction of the vibration signal with a small number of sampling values. Second, the time domain signal composed of all scattered light at the vibration source is analyzed to complete the measurement of vibration frequency. Finally, a heterodyne Phi-OTDR system is built, using PZT to simulate the vibration source. And 36 scattered light information is continuously collected at the frequency of 100 Hz and 500 Hz. The experimental verification of the CS method in this paper is carried out, besides, the signal-to-noise ratio (SNR) is compared with the traditional difference method, Empirical Mode Decomposition (EMD) method, and Variational Mode Decomposition (VMD) method. The experimental results show that the SNR of this method is improved to 40.41 dB and 30.62 dB, the optimal spatial resolution is 9m, and the maximum relative error of frequency measurement is 8.1%. Compared with the results of traditional I/Q demodulation, the frequency information obtained by the two methods is consistent, and there is no obvious deviation from the actual frequency of PZT. While improving the SNR of the system, this method can greatly simplify the signal processing process and improve the positioning accuracy of the system, which has a certain practical application value in the fields of infrastructure monitoring, resource exploration, and vibration detection.