Spcetral Broadening Effect Of FBG And Its Application In Rail Sensors

Track sensor system plays an important role in the detection for the entire railway operations. A lot of information about safety and efficiency can be got by testing track status. At present, the track circuit and electromagnetic axle equipment are mainly used to complete the monitoring of the track signal in China, however, there are many defects in it, such as weak electromagnetic interference. Monitoring devices based to FBG can overcome these shortcomings. Researchers are gradually concern on it, and use it in practical. This paper presents a novel sensing scheme based on fiber grating, this scheme can count on, orientation, weight, the orbital axis, besides, this paper proved that the experiment feasible.In this paper, theoretical analysis of FBG and the design of rail monitoring were discussed. At first, from coupled-mode theory in FBG and Transfer matrix method, we derived FBG reflection spectrum curve; Then we used the coupled mode theory in FBG with uniform and non-uniform axial stress and discussed their FBG sensor model respectively, especially, the reflection spectrum analysis in non-uniform axial stress provides a theoretical basis for the experiment later.The experiment was discussed in two parts, the first one is to verify the spectrum of FBG broadening effect, we used a simple beam model to make a non-uniform axial stress experiments in the laboratory, at the same time, temperature and axial uniform sensor was comparison; the second one was the verification in the track sensing program for the FBG, we tested the strain on the rails by sensing devices in the Key Laboratory of Road and Railway Engineering, and got the correspondence of strain variation and the reflected light power.The experimental analysis in the spectrum broadening effect and the strain on the tracks was used to prove the feasibility of grating sensor design.The proposed FBG sensing devices can be used to track axle, positioning and monitoring of weight, etc., its the advantages include high-speed detection based on strength demodulation, simple structure, free from electromagnetic interference and does not require temperature compensation, and a better application prospects.