Research On The Bi-layer Metal Membranes Temperature Sensing Technology Based On Fabry-Perot Cavity Structure

Temperature is one of the most fundamental measurement parameters. Temperature measurement in high accuracy, safe, and reliable manner has great significance in the industry and agricultural production, especially in the flammable and explosive situation. Accordingly, it is important to research and develop a high-accuracy and miniature temperature sensor that can be applied in the flammable and explosive environment. A novel Fabry-Perot temperature sensor has been designed in this paper, it is based on the Fabry-Perot cavity structure and multi-light interference theory. Fabry-Perot cavity's upper mirror is made up of bi-Iayer membranes and lower mirror is formed by polished fiber end, bi-layer membranes will be deflected in response to changes in ambient temperature because of 'Bi-coating Effect1, then Fabry-Perot cavity depth will be changed, Fabry-Perot cavity ' s reflectance property will be modulated in step, so when the output light intensity is measured, measured temperature can be determined.Firstly, The theoretical model of Fabry-Perot cavity adapted to the temperature sensing was built and developed in this paper, the sensor structure was optimized: including bi-layer material selection and the sensor's elements size, and the performance curve of output light intensity versus measured temperature is given by ANSYS simulation. Secondly, Thermalstress of the sensor structure was analyzed by finite element software ANSYS, the characteristic of the displacement versus the applied temperature of bi-layer metal membranes is studied, and the technique of manufacture of the fiber Fabry-Perot sensing head was introduced. Thirdly, the constitute of experiment system and experiment method have been introduced in detail, the experiment was been proceeded and the result of experiment was been analyzed according to the request, the experimental results have shown that the sensor's average sensitivity can get 66.82nw/℃ and its accuracy is ± 0.7 % when the applied temperature range varies from 0℃ to 80 ℃. Finally, according to theories and experiment result of bi-layer metal membranes temperature sensing, a silicon micro-mechanical Fabry-Perot temperature sensor with resembling structure as the experimental temperature sensing has been designed at the end of the paper, the sensor structure was optimized and the technique of manufacture has been discussed, and the performance of the sensor has been simulated, the results from theoretical analysis indicated that the sensor's sensitivity can get 300nw/ ℃ and the size of sensor is only 500um x 500um when measured temperature range varies from 0℃ to 100℃. In addition, output light intensity of the sensor varies in good linearity with applied temperature.