Investigation Of Silicon-based Microstructure Fabry-Perot Interferometric Optical Fiber Sensing Technology

Along with the proposal of the maritime power strategy,China has continuously increased the development,utilization,protection,and control of the marine field to enhance its strategic layout in the world's marine field.Monitoring and measuring various environmental parameters of the ocean,including temperature,salinity,depth,flow velocity,etc.,is an important source of information and guarantee for marine military activities and marine development.Optical fiber sensing technology has attracted much attention in the field of marine sensing applications in recent years due to its many advantages such as small size,lightweight,multiplexing capability,remote measurement capability,and immunity to electromagnetic interference.Fabry-Perot(FP)interference fiber optic sensor is an important branch of the fiber optic sensor.Its compact sensor structure helps to achieve high spatial resolution detection.Aiming at the application requirements of high resolution and multi-parameter measurement in marine sensing field,this dissertation focuses on the research of silicon-based microstructure Fabry-Perot interferometric optical fiber sensing technology.This dissertation takes the optical fiber FP interference as the theoretical basis and uses the etching technology in Micro-electro-mechanical systems(MEMS)as the technical means to fabricate the main structure of the silicon-based microstructure FP interferometric optical fiber sensor.Combining the advantages of silicon materials and the temperature sensing characteristics of fiber Bragg grating(FBG),this dissertation has studied the silicon-based microstructure FP interference multi-parameter optical fiber sensing technology,large dynamic range FBG assisted unambiguous peak identification of silicon-based microstructure optical fiber temperature sensing technology,and high resolution silicon-based microstructure optical fiber current sensor based on Ohm heating principle.The researches of these sensing schemes focused on the structure design,parameter demodulation,function optimization,and other aspects.The major contents of this dissertation are summarized as follows:1.For the demand of multiparameter sensing applications,a silicon-based microstructure FP interferometric multi-parameters optical fiber sensing scheme is designed and implemented.Establishing a theoretical model of silicon-based microstructure FP interferometric optical fiber sensor,which lays a theoretical foundation for the design of silicon-based microstructure FP interferometric optical fiber sensor.Based on MEMS micromachining technology,a hollow core silicon-based microstructure is designed.Combined with the advantages of multi-channel synchronous sensing of multi-core fiber and its fan-out devices,a silicon-based microstructure FP interferometric multi-parameters optical fiber sensing scheme is proposed.Based on this scheme,a temperature/pressure sensor based on UV curing adhesive filling is designed and implemented.The experimental results show that the sensor can be used for simultaneous measurement of temperature and pressure,proving the feasibility of silicon-based microstructure FP interferometric multi-parameters optical fiber sensing scheme.2.In order to solve the phase ambiguity problem of the FP interference based optical fiber sensor in the process of wavelength demodulation,FBG assisted unambiguous peak identification of silicon-based microstructure optical fiber temperature sensing technology is designed and implemented.The sensing technology scheme utilizes the absolute measurement characteristics of FBG to realize the accurate demodulation of the sine spectrum wavelength of the FP interference fiber sensor while retaining the advantages of high sensitivity and high resolution of the silicon-based microstructure FP interference fiber temperature sensor.The experimental results show that the sensor design can increase the temperature measurement range of the silicon-based microstructure FP interference fiber temperature sensor to 200?,which is more than four times of the original temperature measurement range,and the sensor temperature resolution can reach 3.3mK,which is one-sixth of FBG temperature resolution.3.Based on the principle of Ohmic heating,an air microcavity FP interferometric optical fiber current sensor is designed and fabricated.Through the heat exchange conservation and lumped parameter model,the relationship between the interference wavelength of the sensor and the current is theoretically derived.According to the low resistance characteristics of metal Tin,a piece of Tin bar is melted into a spherical shape and inserted with two metal wires,so that it could simultaneously serve as a current conducting element and a heat conversion element.The temperature and current sensing characteristics of the sensor are studied.The experimental results show that the shorter the length of air microcavity,the higher sensor sensitivity.Through the thermal stress analysis method,the reason why the sensor sensitivity changes with the length of FP cavity is theoretically analyzed.4.For the demand of high resolution current measurement applications,metal tin balls and silicon-based microstructure FP interferometric fiber optic sensors are combined to design and implement an FP interferometric fiber optic current sensor.To solve the temperature cross-sensitivity problem of current sensors based on the principle of ohmic heating,an FBG is applied to temperature compensation of this sensor.The temperature compensation effect of FBG is studied.The difference of sensor current resolution between FBG temperature compensation and no temperature compensation is compared and analyzed.when the current is 0.3 A,the current resolution can reach 1.26×10-3 A under temperature compensation.Finally,the contents and the innovations of the dissertation were summarized,and the future work was described.