Research On Refractive Index And Temperature Sensing Technology Of Photonic Crystal Fiber

The fiber optic sensor has the advantages of compact structure,easy manufacturing process and accurate measurement.It is widely used in steel production,biological sample testing,drug analysis,food safety testing and other fields.Among them,Photonic Crystal Fiber(PCF)has attracted much attention in the field of optical fiber sensing due to its unique structure.Firstly,the paper introduces the research background and significance of PCF sensing and the classification and light guiding mechanism of PCF.Then it summarizes the research situations of PCF sensing based on Mach-Zehnder interference,including three aspects,namely,refractive index sensing technology research,temperature and multiparameter sensing research,and strain curvature gas concentration research.In addition,it introduces the excellent characteristics of PCF and makes the theoretical analysis of PCF sensing based on Mach-Zehnder Interference(MZI)structure.Based on the basic theory of Mach-Zehnder interference structure,a photonic crystal fiber sensor with two-waists structure is proposed to realize the sensing measurement of refractive index and temperature.The experimental research results are as follows:(1)A microfluidic control device is designed in this paper.A novel two-waists photonic crystal fiber sensor is proposed to measure the refractive index by separately aligning both ends of the photonic crystal fiber with single mode fiber(Single Mode Fiber,SMF).The welding and the two-waists processing of the photonic crystal fiber form a SMF-TWPCF(TwoWaists Photonic Crystal Fiber)-SMF sensing structure,and Mach-Zehnder interference is formed during the transmission of the structure.In the experiment,the microfluidic control device can be used to mount the optical fiber,and the change of the spectrum can be observed and analyzed by changing the NaCl concentration in the microfluidic control device.The experimental results show that the resonance valley wavelength of the interference spectrum shifts with the increase of the external refractive index,and the high refractive index sensitivity of 263.469nm/RIU is achieved in the refractive index range of 1.3374 to 1.3477,which has goodlinearity.(2)This paper uses the SMF-TWPCF-SMF structure to design a new two-waists PCF sensor,which realizes the measurement of temperature,and Mach-Zehnder interference is formed during the transmission of the structure.In the experiment,the treated PCF was sealed with a metal casing and filled with alcohol,and the change of the interference spectrum was observed by changing the external temperature.The experimental results show that with the increase of temperature,the resonance valley wavelength of the interference spectrum appears blue shift,and the temperature sensitivity in the temperature range of 76 °C ~ 80 °C is 0.3379 nm / °C,which has excellent linearity.Both of the above sensors have the advantages of small volume,good stability,high sensitivity,easy preparation,etc.,which have a longer sensor service life and more practical value when compared with the taper structure.