Research On Intrusion Detection Technology Of Perimeter Security System Based On Phase-shifted Fiber Grating Sensing

With the increase of social wealth and the improvement of people's living standards,people's demand for eliminating or reducing threats from outside and seeking effective security is becoming more and more intense.Traditional electrical products,such as infrared radiation,leakage cable and electronic pulse fence,are all vulnerable to electromagnetic interference and environmental impact,resulting in inaccurate location and other shortcomings.It has been increasingly unable to meet people's needs for security.The conventional uniform Prague grating tends to distort the spectral pattern when measuring the high order strain,and the problems such as the failure to measure the effective information are serious.As the phase shifted FBG,as a non-uniform grating,retain the advantages of Prague grating,it still has good characteristics of Prague grating.It is worth further research.The main work and innovation results of this paper are as follows:(1)The basic theory of phase shifting fiber Bragg grating is studied,and the transmission matrix method is used to simulate the spectral characteristics of phase shifting fiber Bragg grating.Based on the MATLAB software platform,the influence of phase shifted fiber grating phase-shifting point location a,phase shift volume,refractive index modulation depth and grating length L on the reflection spectrum characteristics of phase-shifting fiber grating is studied and analyzed in detail.The simulation results show that the a=0.5,and L=10mm,phase shift fiber Bragg grating has the best reflection spectrum,and the central wavelength of phase shift point is the most easily observed.(2)The transfer matrix method is used to select the appropriate parameters to simulate the temperature and strain of the phase shift fiber Bragg grating sensor.The range of strain measurement is from 0?2100?? and the temperature range is-25 to 100°C.And then use the OptiGrating software simulation,acquisition of sensor data of phase shift fiber grating temperature and strain,and on this basis,the application of CFTOOL tools to the regression analysis of the measured data,the sensitivity of phase shifted fiber grating temperature and strain phase shifting point center wavelength were obtained.The strain sensitivity of the phase shifted fiber Bragg grating is 1.204pm/??,and the relative value of FBG is reduced by 0.005pm/?? which is negligible.The temperature sensitivity is measured at 12.4pm/?.The theoretical value of FBG is increased by 4.85pm/°C.The experimental results also show that the grating reflectivity varies irregularly with the influence of strain and temperature,so the reflectivity has no reference value in the sensing of phase shifted grating.(3)In view of the shortcomings of traditional perimeter security system,such as poor location and so on,combined with the need for security in modern society,a perimeter security system based on phase shifted fiber grating sensing is designed in this paper.The system is divided into four modules:sensing detection part,signal processing platform,intrusion risk processing system and intrusion database server side.In this paper,the sensor detection system is designed for sensing detection part.First,we design the structure and mode of the sensor,and design a vibration sensor based on phase shifted fiber Bragg grating based on the principle of single point elastic rope.According to the theoretical analysis results,we determine the length of optical fiber,mass and size of the sensor.According to each function module,the function,work flow and realization method are expounded.At the same time,in order to display the system more intuitively,the software platform interface of the system is simulated and simulated.