Distributed Acoustic Sensing System Based on Inserting-Zero Golay Coding With Ultra-Weak Fiber Bragg Gratings

A distributed acoustic sensing (DAS) system based on ultra-weak fiber Bragg grating (UWFBG) array is proposed and experimentally demonstrated by Inserting-Zero (IZ) Golay coding. The system uses 1.5 km UWFBG as the sensing fiber, and extracts phase information through heterodyne detection and IQ demodulation. The Golay coding pulse sequence are used as the modulation signal to improve the system signal-to-noise ratio (SNR), which is benefited from the good autocorrelation characteristics of Golay code. The experimental results display that the DAS system based on Golay coding can effectively reduce the noise level, and the SNR of the system increases by 4.6 dB compared with the individual pulse system. Every bit of Golay coding sequence is inserting one bit "0" can decrease the inter-symbol crosstalk (ISC), and the SNR is further improved by 2.7 dB, and reaches 62.2 dB at 100 Hz. The proposed system has a good response ability of distributed sensing and a good linear characteristic with the coefficient of 0.9966.