Research on Distributed Optical Fiber Vibration Location Algorithm Based on Variance Threshold
Vibration event positioning is an important issue in the study of distributed fiber optic vibration sensing system,a variance threshold algorithm is proposed to locate vibration events based on the phenomenon that fiber optic perturbation events cause an increase in the confusion of the optical time-domain reflectance curves corresponding to the perturbation and its subsequent positions,which leads to the convergence of the cumulative mean curve in the time-domain.The method firstly sets the threshold by analyzing the variance change rule of the optical time-domain reflection curve caused by the perturbation event,and sets the data window at the end position of the optical time-domain reflection curve to check whether there is a vibration event or not.If there is a vibration event,the data window slides to the front of the optical time-domain reflection curve to calculate the variance.According to the set variance threshold,the vibra-tion event location before and after the transition point is determined,so as to locate the vibration event.The distributed optical fiber vi-bration system is experimentally constructed,and a positioning accuracy of±4 m is achieved over a 16 km optical fiber range.Compared with the commonly used difference-by-difference location method,the method proposed adds time-accumulated averaging and attenuation coefficient compensation to the data processing algorithm,which overcomes the error caused by random fluctuations of Rayleigh scatter-ing signals and thus reduces the false alarm rate.
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