The Application Of Fiber Bragg Grating In High-speed Railway Foreign Invasion Monitoring System

The railway is the critical infrastructure of our country, which is closely related to China’snational economy. With the rapid development of China’s railway construction, China’shigh-speed railway construction scale and technical level have been walking in the forefrontof the world. However, the corresponding disaster prevention and safety monitoring system isnot mature, which is still in researching, discovering and consummating. The foreign invasionmonitoring system is an important component of disaster prevention and safety monitoringsystem for high-speed railway. It is mainly used to monitor the road across the railwaybridges, tunnels ports, highways and railway parallel, the railway crossing the mountainwhere may occur foreign invasion such as avalanches and rock fall.On the basis of advantages and disadvantages of existing high-speed railway foreigninvasion monitoring system, this article provides foreign invasion monitoring system based onfiber grating sensing technology. The main research contents are as follow:Firstly, the paper studies the sensing unit of high-speed railway foreign invasionmonitoring system. It analyzes the transmission characteristics of the fiber Bragg grating fiberBragg grating with coupled mode theory, and analyzes longitudinal strain, transverse strainand temperature changes of FBG. With Matlab, the paper simulates the reflective properties,strain and temperature characteristics of the fiber Bragg grating.Secondly, according to the demand of high-speed railway foreign invasion monitoringsystem, the article proposes a mixed multiplexing mode with WDM and SDM, to increase thenumber of fiber Bragg grating sensor multiplexing and achieve distributed monitoring systemwith the same light source bandwidth, grating bandwidth and measuring range.Thirdly, the paper studies the demodulation unit of high-speed railway foreign invasionmonitoring system. On the basis of several used demodulation methods of fiber Bragg grating,the paper emphasizes the tunable F-P filter, expounds the basic principle and simulates itsdemodulation process with Matlab.Finally, this paper uses the physical models simulating retaining wall and passive net.Arrange monitoring points, load stress, measure the micro-strain of intrusion points and judgethe possible position of foreign invasion. The result shows that the application of Fiber BraggGrating in high-speed railway foreign invasion monitoring system is entirely feasible and hasgreat development prospects.