Research Of Dual M-Z Optic Fiber Positioning Sensing System

With the continuous development of optical fiber sensing technology,dual Mach-Zehnder(M-Z)optical fiber positioning sensing technology has also received extensive attention..With its advantages of low cost,simple structure,strong anti-interference ability and long distance detection,it has been widely used in large-scale construction projects,perimeter security,pipeline detection and other fields.research work in the following aspects:First,we analyse the influence of the light source on the interference output of the dual M-Z optical fiber positioning sensing system.The analysis results show that the size of the coherent length of the light source will cause the amplitude of the interference output to decrease,and even the interference phenomenon cannot be observed;he fluctuation of the center frequency of the light source will cause an additional delay value into the interference output.We then explore the interference output of the system under two different lasers.Secondly,we analyze the effect of birefringence on the dual M-Z fiber positioning sensor system.The random polarization state change caused by birefringence reduces the correlation between the two interfering signals output by the system,resulting in the failure of positioning function.Then we explore positioning result of the system with or without a polarization controller,the experimental results show that after reasonable control of the polarization state,the system positioning is more accurate and the positioning stability is higher.Then,we use four smoothing algorithms: median filtering,moving average filtering,Gaussian filtering and Savitzky-Golay filtering,to reduce the noise of the original interference signal;compare and analyze the effect of the four smoothing algorithms on the restored data,and we select Savitzky-Golay filtering as the The filtering method in this paper.Third,we analyze the positioning results of the cross-correlation algorithm when processing different boundaries,and obtain that when the boundaries are different,the cross-correlation algorithm will get different delay values.n order to eliminate the influence of the boundary as much as possible,we use window-type cross-correlation algorithm,and verify the algorithm can calculate the delay value.Finally,we build an experimental platform for intrusion interference experiments,using a small iron rod to simulate intrusion interference signals.The difference in the distance((35)x)between the two photodetectors to receive the signal can be approximated as the length of the sensing fiber.We test five kinds of optical fibers of 20 kilometers,10 kilometers,5 kilometers,2kilometers,and 500 meters,The average positioning results obtained were 19683.5m,9998.6m,4166 m,2470.6m,459.2m.