Research On Sensor Performance Based On Combination Of Optical Fiber Microstructure And Sensitive Materials

In recent years,thanks to the development of information,materials,micro-processing technology and other disciplines,more and more kinds of optical fiber sensors have been developed.Many optical fiber micro-structure sensors based on smart sensitive materials have been proposed,which greatly enriches the application fields of optical fiber sensors.Compared with traditional electrochemical sensors,optical fiber sensors have the characteristics of non-electricity,electromagnetic interference resistance,high temperature resistance,low cost and high sensitivity,which make them possess unique application advantages in monitoring of environmental parameters such as temperature,humidity and hydrogen.At present,optical fiber temperature,humidity and hydrogen sensors still have some problems,such as low sensitivity,complex fabrication process,high cost and poor stability,which seriously restrict the further development of optical fiber temperature,humidity and hydrogen sensors.Therefore,in view of these problems,researchers are constantly putting forward new improvement methods to promote the continuous development of optical fiber sensors.In this paper,three different types of optical fiber sensors are developed based on the sensitive characteristics of different materials and the unique advantages of optical fiber micro-structure,which can be used to measure temperature,humidity,hydrogen and other fields.The main contents of this paper are as follows:?1?Using the thermo-optic effect of polydimethylsiloxane?PDMS?material combined with the surface plasmon resonance?SPR?characteristics of fiber optics,a SPR-type fiber optic temperature sensor based on PDMS material was developed.Firstly,a layer of gold film was coated on the side of the multimode fiber-photonic crystal fiber-multimode fiber?MMF-PCF-MMF?structure by magnetron sputtering technology.By studying the influence of different PCF length and gold film thickness on the performance of the sensor,a better sensing probe was obtained.Compared with the multimode fiber-single mode fiber-multimode fiber?MMF-SMF-MMF?structure,the superior characteristics of PCF as the sensing region are further confirmed from the theoretical and experimental points.Finally,a layer of PDMS material was coated on the surface of the sensor probe with better performance,and the SPR temperature sensing probe was assembled.It has a good response to temperature.The experimental results show that the sensitivity is-1.551 nm/?in the temperature range of 35-100?.?2?Using the principle of moisture absorption and expansion of polyimide combined with the principle of Fabry-Perot?FP?interference,a FP-type optical fiber humidity sensor based on polyimide was developed.The principle of FP interference is analyzed theoretically,and the theoretical humidity value of the FP humidity sensing probe is given by calculation.The experimental results show that the sensitivity of the sensor in the humidity range of 20%RH-90%RH is 22.07 pm/%RH,which is very close to the theoretical value.At the same time,by introducing Fiber Bragg Grating?FBG?into the system,the effect of temperature on FP humidity sensor is compensated by utilizing the characteristics of FBG which is insensitive to humidity but sensitive to temperature.Through mathematical deduction,the temperature compensation formula is given,and the reliability of the temperature and humidity integrated system is further verified from the experimental point of view.?3?Using the principle of hydrogen absorption and exothermic of Pt/MoO₃material combined with the temperature sensitive characteristics of optical fiber FP sensing probe,a FP-type fiber optic hydrogen sensor based on Pt/MoO₃ material was developed.The fabrication method of the FP temperature sensing probe is optimized from the process,and the effects of filling thickness of PDMS material and length of air cavity on the performance of the sensing probe are compared and analyzed.The Pt/MoO₃ material was coated on the side of the FP temperature probe with better performance to prepare the FP hydrogen sensitive probe.The sensitivity of the sensor was-6.20 nm/%under the condition of 0%-1%hydrogen concentration.