Design And Application Of High Sensitivity Sensor Based On Cascade Long-period Fiber Grating

In recent years,fiber grating has been used to fabricate various high-sensitivity sensors due to its advantages of low insertion loss,high accuracy of response to disturbance of the surrounding environment,corrosion resistance and simplicity of fabrication.It has attracted extensive attention from experts and scholars at home and abroad in the field of optical communication and sensing.Long-period fiber grating(LPG)can couple the core fundamental mode with the forward propagation cladding mode,resulting in a series of attenuation peaks in the transmission spectrum.This feature will be more widely applied in the field of communication and sensing.In this paper,Kr F excimer laser is used to fabricate long-period fiber gratings with different structures,and the sensing characteristics of temperature,refractive index and magnetic field are studied by using the long period gratings.The specific research contents of this paper are as follows:In this paper,the development and properties of fiber gratings are briefly introduced.The influence of the disturbance of the external environment including refraction index,temperature and magnetic field on the long-period fiber grating is analyzed theoretically.Then,this paper expounds the method of long period fiber grating,which aimed at different periods and different structure types of long period grating for preparation,especially through point by point by using excimer laser carving work out near the turning point in the phase of long period fiber grating(PMTP).And the aging characteristics of LPG for theoretical analysis and experimental research.Finally,the sensing characteristics of LPG near PMTP were studied in depth,and a cascade long-period grating with high sensitivity was designed.Its spectrum was composed of a series of narrowband resonance peaks,and it had the characteristics of high quality factor(Q-Factor)and high sensitivity at the same time.