Research On Dual-parameter Sensors Based On Fiber Microstructures

In recent years,with the gradual maturity of new micro structured fiber and fiber microstructure technology,fiber-optic microstructure sensor have occupied a place in the field of fiber sensing because of its high compactness and high flexibility.As the two main components of fiber-optic microstructure sensors,fiber grating and fiber interferometer are suitable for different sensing requirements due to their absolute physical quantity measurement and high sensitivity.However,both fiber-optic sensor devices have the cross-sensitivity characteristics of the measured parameters and temperature.In order to combine the advantages of fiber grating and fiber interferometer,solve the problem of cross-sensitivity between the measured parameters and temperature,and adapt to real-time accurate measurement of other parameters in the case of temperature disturbances.In this dissertation,a strain-temperature composite sensor based on overlap splicing technology and fiber grating inscribed technology is fabricated by combining fiber Bragg grating with Fabry-Perot interferometer.A side hole fiber bending-temperature composite sensor based on misalignment splicing technology and fiber grating inscribed technology is fabricated by combining fiber Bragg grating with Mach-Zehnder interferometer.A side hole fiber liquid level-temperature composite sensor based on etching technology,side polished technology and fiber grating inscribed technology is fabricated by combining fiber Bragg grating with Mach-Zehnder interferometer.The main work is as follows:Firstly,this dissertation combines the fiber Bragg grating and the Fabry-Perot,and uses the fiber splicing micromachining technology and the fiber grating inscribed technology to fabricate the spherical fusion joint FBG-FP cavity structure with different overlap conditions,which is controlled by the overlap parameters of the fusion splicer.The formation mechanism of the FP cavity,the stress and temperature sensing principle of the structure are analyzed.The relationship between the overlap and the profile of the spherical structure is established by the principle of volume conservation,which provides a theoretical basis for the establishment of the mechanical model of the structure;Combined with mechanics finite element simulation and coupled mode theory,the spectral shape changes during the stress sensing process are reversed,the feasibility of stress-sensing characteristics is reversed.Finally,the stress and temperature sensing characteristics were tested,the experiment results were in good agreement with the simulation results,and the two-parameter sensing of strain and temperature is realizedSecondly,this dissertation combines the fiber Bragg grating and the Mach-Zehnder interferometer,and uses the asymmetric structure of the side-hole fiber and the fiber misalignment splicing technology to construct the asymmetry in two mutually orthogonal dimensions.The sensing principle of the structure to realize two-dimensional bending sensing is analyzed.A two-dimensional bending sensor demodulation process with the visibility and the resonant wavelength of the interference spectrum is proposed,and its feasibility is verified by experiments.The FBG inscribed technology is used to realize the temperature compensation of the sensor.Finally,its bending and temperature sensing characteristics are tested,the simulation results are in good agreement,and the two-parameter sensing of bending and temperature is realized.Finally,this dissertation combines fiber Bragg grating and Mach-Zehnder interferometer,and uses chemical etching technology to adjust the distance between the air hole and the core of the fiber,which can be used to change the interaction between the core and the external environment.The side-hole fiber is side polished by the fiber side polished technique,so that the core mode can contact with the external environment.The misalignment splicing technology is used to misalign the side-hole fiber to build a Mach-Zehnder interferometer.The sensing principle of the sensor is analyzed.The relationship between the structural parameters of the side-hole fiber,the sensitivity of the liquid level and the quality of the interference spectrum was simulated by the finite element software,and the sensitivity of the liquid level sensing was optimized and improved.The FBG inscribed technology is used to realize the temperature compensation of the sensor.Finally,the liquid level and temperature sensing characteristics are tested,and the simulation results are in good agreement,and the two-parameter sensing of liquid level and temperature is realized.