The Improvement And Optimization Of Optical Fiber Temperature Measuring System Based On Raman Scattering

As a special temperature measurement technology,the distributed optical fiber temperature measurement technology has the advantage of comparison with ordinary temperature sensor.Optical fiber is not only the transmission medium but also the sensing medium,which can effectively save the system resources and space.And it also has the characteristics of anti electromagnetic interference and anti combustion.The distributed optical fiber temperature sensing technology by optical fiber measurement of temperature field distribution of a whole area,effectively avoid the traditional dot by dot matrix sensor to measure the temperature,resulting in the spatial resolution is too low,and difficult wiring problems.Distributed optical fiber temperature sensing system mainly depends on the intensity of Raman scattering light to detect the temperature.However,in practical applications,the signal intensity of Raman scattering is very weak,and it is still in a strong noise environment.Therefore,it is the key to the application of the technology to enhance the effective signal and eliminate the noise.In this paper,the signal enhancement of optical fiber temperature measurement is taken as the core content,and the optical fiber temperature measurement system is optimized:1.Basic theory of Raman scattering,respectively,proposed single channel demodulation algorithm,dual channel demodulation algorithm and based on dual demodulation algorithm presents a special linear algorithm,are analyzed for each algorithm,and concludes the advantages and disadvantages and applicable occasions.In order to eliminate the influence of the light source power fluctuation and the temperature drift of the APD,the demodulation algorithm is used to demodulate the temperature.2.The basis of the existing system hardware framework,the key performance indicators of the system are analyzed.Under the premise of the influence of each module on the performance index,the appropriate module is selected to build the system.3.The signal processing technology of distributed optical fiber temperature measurement system is studied.The noise sources of the system are analyzed,and the algorithm is used to deal with the collected Raman signals by using the cumulative average algorithm,the wavelet transform and the Kalman filter algorithm.4.According to the Rayleigh noise to deal with distributed optical fiber temperature measurement system,the theoretical analysis respectively in single channel and dual system,analysis of the effect of Rayleigh noise measurement accuracy of the system,the temperature sensitivity and temperature resolution.Finally,a new algorithm based on multi segment reference fiber to eliminate the Rayleigh noise is proposed.5.The upper computer software of distributed optical fiber temperature measurement system is designed,and a lot of experiments are done.The functions of data acquisition and processing,temperature calibration,temperature display,abnormal alarm and data storage are designed.The experimental results show that the system can achieve the spatial resolution of 1.5m,the accuracy of temperature measurement is 2 DEGC in the range of 3000m.