Application on Seepage Monitoring by Multi-point Optical Fiber Grating Temperature Measurement System

The structure of the multi-point Fiber Bragg Grating (FBG) temperature measurement system is presented in this paper. It uses the wavelength demodulation method which applies In GaAs detector array to measure the light intensity to monitor the situation of the seepage in the dam. According to the laboratory data, analyze the possibility of the multi-point fiber grating sensor system and the reliability of the measured data, the result shows that the wavelength-temperature response sensitivity of the fiber grating sensor can reach 0.0091 nm/°C of the temperature field in the dam. Using the electric heat pulse method to heat the soil around the sensors is adopted in engineering application, it forms the temperature difference with the water, the engineering result shows that the method which uses fiber grating to detect temperature difference can apply to monitor seepage. Consequently, this system can realize the positioning of concentrated seepage points in the dam and automatic monitoring. Compared with conventional instruments, the fiber grating sensing monitoring system has obvious advantages in resistance to thunderbolts and disturbances.