A Study On Distributed Optical Fiber Temperature Measurement System Based On Raman Scattering

Distributed optical fiber temperature measurement system based on Raman scattering is a new type of temperature sensing system developed in recent years, which can on-line measure the spatial temperature field utilizing single sensing fiber.Compared with the traditional temperature measuring system, Raman temperature measurement system has several obvious advantages, high spatial resolution and temperature resolution. Real time monitoring temperature, temperature information refreshed at regular intervals, ensured measurement data timely and effectively. In addition, the distributed optical fiber Raman temperature measuring system has the advantages of corrosion resistance, anti-electromagnetic interference, fire-proof and explosion-proof and long distance transmission, making it advanced than traditional temperature sensor. On account of its unique advantages, distributed optical fiber Raman temperature measurement system has been widely used in aerospace, industrial field, public security and other fields.This paper summarized the current research situation and development trend of the domestic and overseas on the basis of reviewing the development background of the optical fiber sensing technology, pointed out the deficiency of the domestic system in comparison with foreign similar products, established the main research contents of this subject. Based on analysing the back-scattering light of optical fiber, proposed the basic principle of distributed optical fiber Raman temperature sensing system combined with Raman scattering theory and optical time domain reflection(OTDR) technology.Through calculating and analyzing Rayleigh light, stokes light, anti-stokes light as reference light respectively, determined the system selects stokes light as the reference light to demodulate temperature signal.In accordance with the requirements of system design, the parameter of each component were calculated and analyzed. After selecting the appropriate components, a distributed optical fiber Raman temperature measuring system was set up. On the basis of analyzing the influencing factors of the system signal-noise ratio(SNR), established the system using the method that combines cumulative average and wavelet transform method to improve signal-noise ratio of the system. According to the signal demodulation theory, experiments have been carried out to verify the correctness of demodulation scheme. The temperature calibration module was developed based onsubsection temperature calibration method, after analyzing and processing the collected data, completed the system temperature calibration experiment and realized the temperature measurement.In order to verify the feasibility of subsection calibration scheme, the article firstly respectively test the system spatial resolution, temperature resolution, temperature measurement accuracy, stability and repeatability, the response time. The test results showed that within 100℃, the system spatial resolution of 1m, the temperature resolution is better than 1℃, the temperature measurement precision up to ±1℃, the response time is 34 s, the system is stable and reliable and has good repeatability.Secondly, explored and studied on the measurement of the high temperature area in order to be able to monitor the special fields such as oil well, nuclear power plant and so on, achieved the measurement of the temperature of 300℃. Finally, the system was installed and tested, and the test results meet the system requirements, hereby completed the distributed optical fiber Raman temperature measuring system prototype which has excellent performance and significant price advantage.