RESEARCH ON SPACE-TIME MONITORING OF HIGH-SPEED RAILWAY UNDER LINE STRUCTURE BASED ON OPTICAL FIBER VIBRATION MEASURING TECHNIQUE

摘要

Optical Time Domain Reflect Meter (OTDR), has been applied to the detection of disturbance of vibration signal to fiber. During the detection, laser transmitted pulsed light. The incident light backscattered during the transportation process in the fiber. Due to elastic-optic effect and disturbance offiber, the refractive index changed in corresponding place in the fiber, which led to the change of optical phase. Backscattered light intensity changed with optical phase because of interference effect. The location of scattering points can be determined by the time of back optical signal. A trail was operated on a section of railway near Hongqiao high-speed railway station. Optical fiber sensors were installed on six slabs, monitoring the vibration characteristic of slab when the train passed. The relationship between fiber vibration intensity and disengaging was discovered during the trail. Meanwhile, detection methods such as impact imaging method were used to evaluate the area of disengaging in order to validate our proposed method. Experimental results verified that fiber vibration is feasible. The research result provides reliable basis for setting threshold value of slab disease early warning.