Research On Optical Fiber Temperature Sensing System Based On Attenuation Difference Compensation

With the increasing requirements for processing environment conditions in the industrial field,the application of distributed optical fiber temperature sensors that are long-distance,wide-range,and adaptable to harsh environments has become more widespread.However,when the physical quantities(such as temperature,stress,etc.)in the environment where the optical fiber is located change,the temperature measurement value of the system will have a large error,so the temperature measurement accuracy of the system needs to be improved.However,the current accuracy improvement research mostly ignores the difference in the attenuation coefficient of Stokes and Anti-Stokes light in the temperature demodulation method,resulting in a large error in the final temperature demodulation result;In addition,in the demodulation method,only the difference between the essential loss or additional loss of Stokes and Anti-Stokes light is studied,and it is impossible to balance the two,which affects the temperature measurement accuracy of the system.In response to the above problems,the article aims at the temperature measurement accuracy of the sensor system,starting from the traditional temperature demodulation method,establishes a mathematical model of the optical attenuation difference between Stokes and Anti-Stokes,and uses the attenuation difference fitting equation to improve the temperature demodulation method,and On this basis,the Rayleigh noise is eliminated,and the improvement effect of the multi-order fitting equation on the temperature measurement accuracy is compared to obtain the optimal fitting order,and the temperature measurement accuracy is improved by using the optimal fitting order.The main contents of the paper are as follows:First,the sensing mechanism and theoretical model of the distributed optical fiber Raman temperature measurement system are studied.Among the main indicators of temperature measurement accuracy,spatial resolution,temperature measurement distance,time resolution and spatial positioning accuracy,the system temperature measurement Accuracy is the research object,combined with the light attenuation characteristics of Stokes and Anti-Stokes,through the ring temperature measurement mechanism of the sensing fiber,a mathematical model of the difference between Stokes and Anti-Stokes light attenuation coefficients is established.Secondly,build a distributed optical fiber Raman temperature measurement system,set up a ring temperature measurement mechanism of the sensing fiber;use the temperature measurement results of the experimental platform and the mathematical model of the attenuation coefficient difference to obtain the fitting equation of the attenuation difference;in the improved demodulation method Establish a mathematical model to solve the Rayleigh noise,obtain the Rayleigh noise in the system through the signal value and temperature demodulation value of the experimental platform,eliminate the Rayleigh noise on the improved temperature demodulation model,and realize the temperature self-correction;experimental results It shows that when the temperature is in the range of 30??90?,the elimination of Rayleigh noise based on the temperature demodulation method with attenuation difference reduces the temperature error by 7.22?,which verifies the feasibility of improving the temperature demodulation method.Then,the fitting mathematical model of each order of the attenuation difference is introduced into the improved demodulation method,and the temperature error of the improved temperature demodulation method that introduces the fitting results of each order after the Rayleigh noise is eliminated is obtained by comparing the temperature error The optimal model in each order of fitting models,the order corresponding to the optimal model is the first order,and the additional loss of the reference fiber is reduced by the optimal fit order,and the additional error of temperature measurement caused by the fiber in the temperature measurement section The experimental results show that the improved temperature demodulation method under the best fit order can increase the temperature accuracy to 0.90?.Finally,a simple three-dimensional model of the coal mine goaf was built to simulate the oxidation reaction of the leftover coal in the goaf with the exothermic reaction of massive quicklime and water vapor,and the temperature change of the massive quicklime pile was monitored in real time with an industrial thermometer,and the system was analyzed and explored.Temperature measurement effect in a variable temperature environment.The results of simulation experiments verify the applicability of the distributed optical fiber Raman temperature measurement system in engineering and the feasibility of the improved temperature demodulation method that introduces the first-order fitting attenuation difference under variable temperatures.Figure [32] table [0] reference [81]...