Research On Key Techniques Of Microbubble-based Fibre-optical Fabry-perot Sensorsfor High-temperature Application

The measurement and monitoring of pressure and strain has been widely used in many fields of national economy.While in some special fields,such as aero-space engine development,energy oil detection and other projects,it is necessary to overcome the high temperature problems when measure pressure and strain.The mechanical performance of the sensor or the signal in transmission process could be affected or even failed in hash environments,result in inaccurate measurement results.Owing to the advantages of optical fiber sensors,such as small size,light weight,high sensitivity,immunity to electromagnetic interference and hash environments,optical fiber Fabry-Perot sensor shows great potential in the field of stress and strain measurement in high temperature environments.In this paper,according to the Fabry-Perot interference mechanism,two kinds of high temperature fiber Fabry-Perot pressure and stress sensors based on microbubble structure are designed and demonstrated for high temperature environment.And the mechanical properties of the sensor model are also analyzed and simulated to determine the parameters of the sensor.At the same time,we also investigated varieties of method for processing the Fabry-Perot cavity,and we chose an optical fiber fusion splicer to process the entire sensor according to the size of the sensor.Furthermore,a temperature compensation structure is used to reduce the temperature coefficient of the sensor,and the thermal stress simulation of this temperature compensation structure model is conducted by using the multi-physics simulation software.Finally,we analyzed Fabry-Perot cavity demodulation principles,and test the pressure sensor and the strain sensor at room temperature and high temperature by using high temperature-pressure composite platform and high temperature strain testing system,respectively.The sensitivity,stability and temperature coefficient of the sensor were analyzed and discussed.The pressure range of the pressure sensor we tested is atmospheric pressure to 1 MPa,the maximum sensitivity is about 6.4nm/MPa,the lowest temperature coefficient is 0.17pm/°C;the strain range of the tested strain sensor is 0~1000??,the sensitivity is about 0.026 Nm/??,temperature coefficient is about 2.3pm/°C.The experiments show that the optic fiber Fabry-Perot sensors based on microbubble structure high temperature can be used well in the environment of 600?.This paper provides a reference for the future research of high temperature fiber-optic Fabry-Perot sensors.