The Existing Railway Links Up Grounding Wire Anti-Theft System Research Based On OTDR

Nowadays,the microelectronics technology has been applied comprehensively in the railway system.We must not only ensure that the electrical system along the railway has a stable operating environment,but also need to minimize the impact of the lightning current on the electrical equipment by making it be released quickly and effectively.Thus the technology of the railway links up grounding wire has been developed and implemented.And the theft cases of the railway links up grounding wire will lead to a damage in the system grounding,cause the equipment damage and even casualties and other adverse consequences.In order to eliminate such threats and hidden dangers,this paper presents an anti-theft system based on the Optical Time Domain Reflectometer(OTDR),which aims to realize the real-time monitoring of the railway links up grounding wire and to alert and locate the theft.With a view to reducing the frequency of the theft cases and minimizing the economic and security risks.First of all,this paper introduces the researches and achievements of the anti-theft system of the railway links up grounding wire.Then,we combine their advantages and disadvantages as well as the technical characteristics of optical fiber sensing,put forward the anti-theft system based on OTDR.Furthermore,we elaborated the basic theory,working principle,important parameters and other elements of OTDR.Secondly,we deeply analyze the two most important parameters--dynamic range and distance resolution.In order to improve the efficiency of OTDR in practical application,we put forward a method to ameliorate the detection signal by pulse coding technique.And we contrast the performances and SNR gains of several different coding techniques by formulas and simulations,select the C-S composite symbology form them with the most outstanding performance.Furthermore,in order to have better operability and accuracy in the process of signal processing.We point out that the necessity of the application of wavelet transform in this anti-theft system by the comparison among Fourier transform,short-time Fourier transform and Hilbert-Huang transform.And then,we research the analysis and positioning of events on OTDR curve based on this theory.Finally,we focus on the combination of fiber and the railway links up grounding wire.Based on the theory of bending loss of fiber,we propose the scheme that to combine the railway links up grounding wire and single-mode fibers with setting bending joints at given intervals by consider the influencing factor of bending loss and the MATLAB simulation results.From this,we can build the anti-theft system on the basis of whether the bending loss is released.Thereout,we purpose an effective way to combine the fiber optic sensing technology light sensor technology with existing railway situation of China in the practical application.Furthermore,we verified the feasibility of this scheme by simulations of the theft events.