Research On Optical Fiber Temperature And Humidity Sensor Based On Surface Plasmon Resonance Effec

Optical fiber temperature and humidity sensors are widely used in many fields such as medical treatment,environment,biology and physics.They have attracted the attention of a large number of scientific researchers due to their small size,portability,strong antielectromagnetic interference ability and high corrosion resistance.With the development of surface plasmon resonance(SPR)technology,sensors based on SPR have also emerged.SPR sensor is favored by many people because of its superior sensing performance,and optical fiber provides an opportunity for the miniaturization of SPR sensor.In this thesis,a high sensitivity SPR temperature and humidity sensor is proposed by combining SPR with optical fiber and utilizing the temperature sensitive characteristics of polydimethylsiloxane(PDMS)and the humidity sensitive characteristics of polyvinyl alcohol(PVA).The research contents of this thesis are as follows:(1)The influence of different factors on the resonance peak is analyzed by simulation to determine the structural parameters.Then,the refractive index response of the selected structure is simulated and the internal mode field of the fiber is analyzed using Comsol simulation.(2)In this thesis,a single-mode fiber SPR temperature and humidity sensor based on fiber Bragg grating(FBG)is fabricated by combining SPR with FBG.The dual-parameter measurement of ambient humidity and temperature is realized.The sensor removes part of the cladding of the fiber,and then plates silvers outer side of the fiber.Temperature sensing is realized by FBG,and humidity sensing is realized by coating PVA on the surface of the silver film to excite SPR.During the experiment,PVA solutions with different concentrations were prepared,and PVA films with different thickness were coated on the sensing area by the pullup method.The humidity sensing characteristics of PVA films with different thickness were further studied.The experimental results show that the temperature sensitivity of the sensor can reach 0.0203 nm/℃ in the temperature range of 20 ℃-70 ℃,and the humidity sensitivity can reach-0.99 nm/%RH in the humidity range of 30%-80 %RH.The cross sensitivity of temperature and humidity was tested in the experiment,and the humidity measurement results were further optimized by temperature compensation.(3)In order to further improve the sensing performance,a dual-SPR temperature and humidity sensor based on single-mode optical fiber is designed in this thesis.The sensor uses a single-mode optical fiber in the middle of which removes a small section of the cladding,and then silver film is coated on the outside.PDMS and PVA are used as temperature and humidity sensitive materials to realize the double SPR measurement of temperature and humidity.First,the temperature and humidity response is simulated.The simulation results show that the temperature and humidity measurement with double SPR can be realized in theory.There is no mutual interference between the SPR peak of the temperature and humidity.Then,the temperature and humidity response test and cross sensitivity test are carried out on the prepared sensor.The experimental results show that the temperature sensitivity reaches-2.01 nm/℃ in the temperature range of 20 ℃-70 ℃;the humidity sensitivity can reach-4.35 nm/%RH in the humidity range of 30 %RH-78 %RH.Finally,the cross sensitivity of temperature and humidity of the sensor is measured,and the influence of temperature change on humidity measurement is reduced by linear compensation.