Design Of High Sensitivity Optical Fiber Refractive Index Sensor Based On Multilayers

As an optical property of matter,refractive index is closely related to its concentration,density,composition and other parameters.Through the measurement of material refractive index,we can directly or indirectly get a lot of other characteristics of material information,so the accurate measurement of material refractive index has a certain value in many fields.Compared with some traditional methods of measuring refractive index,fiber-optic refractive index sensor has many incomparable advantages,such as smaller volume,more flexible structure change,resistance to electromagnetic interference,not easy to be corroded and so on.In this paper,three kinds of optical fiber refractive index sensors based on multilayers are proposed,and the sensing characteristics of the above three sensors are simulated by MATLAB.The research content mainly includes the following three parts:(1)In this paper,a wavelength modulated fiber surface plasmon resonance sensor based on multilayers is studied.The influence of many parameters on the sensing characteristics of the sensor is simulated and analyzed by MATLAB software.The parameters studied include the diameter of fiber core,the length of sensing area,the thickness of gold film,the type of oxide film and the thickness of oxide film.The results show that the sensitivity can be improved and the resonance wavelength can be tuned simultaneously by adding oxide coating on the surface of the original metal film.When the thickness of magnesium oxide,scandium oxide,tellurium dioxide and titanium dioxide is set to 80 nm,53 nm,45 nm and 40 nm respectively,the sensitivity of the sensor is higher than 9000 nm/RIU,and the resonance wavelength can cover the communication C+L band.On this basis,taking the titanium dioxide film as an example,the refractive index range that can be detected by the sensor with resonance wavelength covering the C+L band of communication is given when the film thickness is different.(2)In this paper,a phase modulated fiber surface plasmon resonance sensor based on multilayers is studied.The influence of various parameters on the sensing characteristics of the sensor is simulated and analyzed by MATLAB software.The parameters studied include the incident angle of light,the thickness of silver film,the type and thickness of oxide film.The results show that the change of refractive index between p-polarized light and s-polarized light can be tuned by adding oxidecoating on the surface of the original metal film.When the film thickness of magnesium oxide,lutetium oxide,scandium oxide and titanium dioxide is set at 68 nm,51 nm,48 nm and 29 nm respectively,the refractive index which causes the phase difference between the two polarized light to change abruptly can be reduced to1.0,that is to say,the sensor can realize the high sensitivity monitoring of the refractive index of the gas.(3)A D-type optical fiber phase modulation sensor based on multilayers is studied.The influence of oxide film type and thickness on the sensitivity of the sensor is simulated and analyzed with MATLAB software.Moreover,the optimum thickness and average sensitivity of different oxide films are given on the premise of different refractive index.