Signal Processing Method Study of Reducing Spectral Noise in Optical Fiber Sensing System
A signal processing method using Blackman window function was proposed to solve the issue of Brillouin frequen-cy shift error caused by noise spectrum leakage in the STFT-BOTDR system based on short-time Fourier transform.Firstly,the STFT-BOTDR system was built,and the Brillouin signal including the low-frequency noise generated by the system frequency conversion module was collected.Then the Brillouin gain spectrum and Brillouin frequency shift distribution demodulated by Hamming window function and Blackman window function were used respectively.The experimental results show that using Black-man window function is more effective than using Hamming window function to solve the phenomenon of Brillouin gain spectrum distortion caused by harmonics caused by spectrum leakage of low-frequency noise in STFT-BOTDR system,and the measurement error of Brillouin frequency shift was reduced.The experimental results show that the Brillouin frequency shift distribution meas-urement accuracy using Blackman window function demodulation on the 1.8 km optical fiber to be measured can reach 1.469 1 MHz.The overall performance of the system was improved,which is conducive to the engineering application of low-cost and medium precision STFT-BOTDR system.
short time Fourier transformBrillouin optical time-domain reflectometerspectrum leakageBlackman window func-tionmeasurement accuracy
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