Optical Fiber Temperature Measuring System Based On Raman Scattering

In recent years,as a means of temperature measurement,distributed optical fiber temperature measurement technology has been widely applied.Compared to conventional electrical temperature sensors,it has been more and more attention with anti-electromagnetic interference,wide measurement area,high stability and simple wiring.In this thesis,aimed at the problem of measurement limited by tradition temperature measurement technique under long-distance condition,a distributed optical fiber temperature measurement system based on Raman scattering technique is developed.The main works of this thesis are as following:1.A linearized temperature demodulation formula is adopted with the theoretical basis of Raman scattering technology.After the Taylor expansion of the Raman scattering formula,the theoretical formula that the anti-Stokes light is sensitive to temperature in the Raman scattering signal is proposed.The method that demodulate anti-Stocks signal with Stocks light is used to eliminate the impact of power fluctuations of light source and APD's temperature drift.It has been simulated and linearized and formulas of temperature demodulation are obtained.2.According to the design index of the system,each module in the system is determined and the laboratory platform is established.Performance parameters in fiber optic temperature cannot be analyzed separately,and it is closely related to module parameters.The appropriate modules are chosen to complete the entire system under the influence of the performance of each module.3.For the collected Raman scattered light that contain noise category,each signal processing technique are analyzed,and a temperature demodulation algorithm is proposed.Several weak signal processing methods suitable for the denoising requirement of the system are analyzed to solve the very weak feature of Raman light that is difficult to collect.An attenuation compensation algorithm is used to compensate for the same ambient temperature of fiber optic cable.The matter of weakening the intensity of Raman light with the fiber distance is solved.4.The design of system software is completed and a large number of experiments are performed.Some function such as data acquisition and processing,temperature calibration and demodulation,temperature display and abnormal alarm,data storage are composed.The experimental result show that the system can reach spatial resolution of 1.5m and temperature accuracy of ± 2 ? when monitoring the 3000m range of fiber.