| The optical fiber MEMS Fabry-Perot sensor is very suitable for measuring the air physical parameters in aviation and other fields because of owing the advantages of high sensitivity,small size,anti-electromagnetic interference,high temperature resistance,high reliability,and mass production.Aiming at the requirement of highprecision and simultaneous measurement of air physical parameters,we carry out research on optical fiber MEMS cascade Fabry-Perot(F-P)sensors.Theoretical analysis of the factors affecting the measurement accuracy in the fiber optic MEMS FP pressure sensor are presented,and a long-term monitoring method of the residual air pressure inside the micro-cavity is proposed.We propose two kinds of high-precision optical fiber MEMS cascade F-P cavity dual-parameter sensors for gas refractive index and temperature simultaneous sensing and for pressure and temperature simultaneous sensing to achieve simultaneous sensing which can also achieve temperature compensation.The major work of this article includes:1.The cascade F-P micro-cavity interference theoretical model and the spectralbased F-P micro-cavity interference hybrid demodulation method are studied.The combination of the Fourier transform method and the spectral peak tracing method is used to achieve large dynamic range and high resolution demodulation results.The effect of this method is 52.8 times more accurate than the traditional Fourier transform method,which lays the foundation for the research of cascade F-P multi-parameter sensors.2.The sensing characteristics of fiber optic MEMS silicon-glass cascade F-P pressure sensors are investigated.We establish a model of the relationship between the deformation of the silicon diaphragm and the residual pressure and thermal stress of the micro-cavity,and we analyze the influencing factors of the sensor's thermal stability.The effects of anodic bonding and thermal-compression bonding on the performance of fiber-optic silicon-glass F-P pressure sensors are experimentally analyzed.Based on the established model,we propose a long-term monitoring method of micro-cavity residual gas pressure without destruction to the sensor structure for screening high-precise sensors.And we experimentally verify the residual gas pressure generated by the two bonding technologies,which provides an effective method for evaluate the bonding quality.3.The optical fiber MEMS cascade F-P micro-cavity gas refractive index and temperature dual-parameter sensor is studied.The silicon-glass-silicon three-layer structure is used to form a cascade F-P silicon cavity and open air cavity for temperature measurement and gas refractive index,respectively.The principle of dual-parameter sensing is analyzed,and the single-parameter temperature-sensitive characteristic of the silicon cavity is used to effectively compensate for the influence of the refractive indextemperature cross-sensitivity error of the air cavity to achieve high-precision,highstability dual-parameter simultaneous sensing.4.A fiber-optic MEMS all-silicon cascade F-P gas pressure and temperature dualparameter sensor is studied.A single-crystal silicon substrate and a silicon diaphragm with the same thermal expansion coefficient with a micro-cavity are directly bonded together to form a temperature-sensitive silicon cavity and a pressure-sensitive vaccum cavity to solve the problem interface thermal stress of the bonding interface.We investigate the principle of dual-parameter cross-sensitivity and temperature sensing characteristics at high temperature.It is proved through experiments that the thermal stress and the residual gas pressure are significantly reduced,and the thermal stability of the pressure measurement is greatly improved.The dual-parameter sensing characteristics of the sensor in a high temperature and wide temperature range are tested.The proposed sensor provides a method for high-precision simultaneous measurement of dual parameters in high-temperature and harsh environments. |
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