A Novel Fabry Perot Fiber Optic Sensor Based On Photopolymer Materials

Since the invention of optical fiber,optical fiber sensing technology has received widespread attention from researchers and has begun to flourish.Fiber optic Fabry Perot interferometric sensors,as an important branch of fiber optic sensors,have been widely used in recent years.Compared to other types of sensors,fiber optic F-P interferometric sensors have the characteristics of relatively low manufacturing cost,simple system,high sensitivity,and strong resistance to electromagnetic interference.They have played an important role in aerospace,oil pipeline detection,biomedical fields,and other fields.Currently,researchers have proposed many methods for manufacturing fiber optic F-P interferometric sensors.Traditional fiber optic F-P interferometric sensors are prepared using corrosion method,arc discharge method,femtosecond laser preparation method,or polymer preparation method.Among them,corrosion method and arc discharge method are the most widely used,but there are problems with low preparation accuracy and relatively complex preparation.Although the femtosecond laser preparation method has high efficiency,the process is relatively complex and requires expensive equipment such as femtosecond lasers,resulting in high preparation costs.The polymer preparation method also has the problem of complex preparation process and low sensing sensitivity.These defects have hindered the further development of fiber optic F-P interferometric sensors.This thesis proposes the use of photopolymer materials to manufacture fiber optic F-P interferometric sensors.This method can reduce the preparation difficulty and cost of fiber optic F-P interferometer,and achieve good sensing performance.This thesis uses photopolymer materials to construct fiber optic F-P interferometric sensors.This free radical photopolymer material will solidify under laser irradiation of 450nm～550 nm,forming a relatively stable and mechanically good optical waveguide structure.The cylindrical optical waveguide structure formed by the photopolymer material solidified on the end face of the optical fiber will form an F-P interferometer sensor together with a single mode optical fiber.Among them,the end face of the single-mode fiber is the first reflection surface of the F-P interferometer,and the end face of the cylindrical photopolymer material is the second reflection surface.Through experiments,it has been proven that when the concentration of eosin in the photopolymer material is 0.05 wt%,the photopolymer material can solidify into the fiber optic F-P interference sensor with the smoothest end face and the best interference performance.At the same time,the length of the cured photopolymer material is100 μm,it can ensure the stability of the sensor structure and achieve good sensitivity.This thesis aims to improve the temperature sensing performance of fiber optic F-P sensors based on photopolymer materials by adding a temperature sensitive material,polydimethylsiloxane(PDMS),to the photopolymer material.Experiments have shown that when the PDMS concentration is below 30%,the photopolymer material can cure normally.This thesis compares the temperature sensing performance of fiber optic F-P temperature sensors with PDMS concentrations ranging from 0% to 30%,and successfully achieves a temperature sensitivity of-1.12 nm/℃ in the range of 20 ℃ to 110 ℃ in experiments.Finally,this thesis conducted stability tests on the sensor,proving that the fiber optic F-P sensor based on photopolymer materials always maintains stable performance during long-term use and continuous temperature changes,with an overall fluctuation of less than 3%,and basically no hysteresis phenomenon.Finally,humidity impact experiments were conducted on the fiber optic F-P temperature sensor based on photopolymer materials.Experiments have shown that the sensor can eliminate humidity crosstalk to a certain extent in a relative humidity environment of 20% to 60%,ensuring the accuracy of the sensor.