Research On Key Technologies Of Distributed Vibration Measurement System Based On Grating Array Sensing In Perimeter Intrusion Detection

The vibration sensing system based on φ-OTDR has been widely studied in the fields of structural monitoring、geological exploration、security and national defense.As a new field in the optical fiber sensing,weak grating array technology overcomes the defects of traditional system which uses optical fiber and strong grating as the sensing unit,and has been widely used in petrochemical plant,bridges and tunnels,building and power station.Perimeter security system combined with φ-OTDR and weak grating array occupies a place in DAS,hydrophone,VSP and large perimeter with its advantages of wide coverage,simple laying and high SNRStarting from the traditional φ-OTDR technology,this paper analyzes the advantages of weak grating array,and explores deeply on perimeter security system based on weak grating and its key technologies.The main research contents are as follows(1)The principle and development of φ-OTDR、grating and weak grating array and demodulation technology are described(2)From the principle of vibration sensing,to the optical system,and then to the corresponding demodulation algorithm,the φ-OTDR technology based on the weak grating array is described in detail,and a set of vibration detection experimental system is built,and the correctness of the idea and the feasibility of perimeter application are verified(3)A new perimeter security system is proposed and built,and he performances of the system are analyzed.The results show that the SNR of the system can reach 30dB,and the detecting distance can reach 50km,which is superior to any existing perimeter product in the market.Finally,the key technologies affecting the system are briefly analyzed(4)Finally,the data processing and algorithm of the fiber-optic vibration measurement system for the perimeter security system are introduced.According to the relevant restrictions based on perimeter product standards,algorithm experiment and the experiment of target signal extraction is carried out.Then,based on a large number of field experimental data,using OpenCV to identify climbing,knocking and car interference signals,the results show that the rate of image-based pattern recognition is nearly 90%,which is of reference significance to reduce the false alarm rate of perimeter system.