Research On Optical Fiber High Temperature Strain Sensor Based On Interferometric Structure And Bragg Grating

Real-time monitor of temperature and strain of the inside of aero-engines is an important technical method to research the working state of aerospace vehicles,which can provide safe and reliable technical support for aerospace vehicles.In recent decades,optical fiber sensors have been rapidly developed due to their many advantages such as small size,fast response speed,high temperature and corrosion resistance,immunity to electromagnetic interference,etc.,and they are widely used in aerospace,industrial smelting and other high-temperature environment field,which have great application value for real-time monitoring the temperature and strain of thermal structures.However,here are still many problems in the optical fiber high temperature strain sensor reported in the current research,researchers have been exploring the strain sensitization method of the sensors,cross-sensitivity issue with temperature and strain and high temperature resistance performance.This paper takes the healthy monitor of temperature and strain inside aero-engine as the research goal,combines two structures of type II Fiber Bragg Grating(FBG)and optical fiber Fabry-Perot interferometer(FPI),manufactures two kinds of optical fiber high temperature strain sensors,and experimentally analyze the response characteristic of the sensors.The sensors are demodulated by the temperature compensated method,which achieves precise measurement of temperature and strain,and the Vernier effect sensitization method is used to increasing the strain sensitivity by a factor of 7.6.The specific research work are as follows:An optical fiber high temperature strain sensor based on FBG cascaded with FPI is manufactured,and experimentally analyze the response characteristic of the sensors.The FBG written by femtosecond laser is encapsulated and protected by a capillary glass tube,which isolates the applied strain and only responds to temperature,while the fiber FPI structure responds to temperature and strain.The sensor is demodulated by the temperature compensated method,which achieves precise measurement of temperature and strain.This method solves the cross sensitivity between temperature and strain of the sensor,and avoids the large error caused by dual-parameter matrix demodulation.The sensor enables accurate measurement of temperature of 1000 ℃ and strain of 350 με.A high sensitivity optical fiber high temperature strain sensor based on vernier effect is manufactured,the operating principle of the sensor is analyzed in detail,the numerical simulation is used to demonstrate the advantage of the vernier effect sensitization,and experimentally analyze the response characteristic of the sensors.The sensor is composed of a FBG encapsulated capillary glass tube cascaded with an optical fiber FPI and then paralleled with an optical fiber FPI through a 3 d B coupler.The FBG encapsulated in the capillary glass tube isolates the applied strain and only responds to temperature,and the envelop of the Vernier spectrum generated by the two parallel optical fiber FPI structures responds to temperature and strain.The sensor achieves precise measurement of temperature and strain,and improves strain sensitivity by a factor of 7.6.The sensor structure is simple to fabricate and suitable for designing optical fiber sensors based on Vernier effect.This paper aims at the research of optical fiber high temperature strain sensor,which provides important technical support for healthy monitor of temperature and strain inside aero-engine,which is of great significance.