Research Of Asymmetric Double Mach-Zehnder Distributed Fiber Perimeter Alarm Technology

For the the advantages of high recognition rate,security,stability and simple structure,The distributed optical fiber alarming system has been widely used in the field of perimeter alarm.Especially in the field of petrochemical industry,it has incomparable advantages over the other perimeter alarm technologies.And then,we make this technology with video,infrared,speech technology as fusion linkage,that can brought a broader application scenario.This paper mainly studies a distributed optical fiber sensing technology based on Asymmetric Dual Mach-Zehnder Interferometry(ADMZI)structure and its application in perimeter alarm.At the same time,combined with the actual engineering environment to carry out related composite monitoring technology research.Based on a review of the research development at home and abroad,the paper focuses on the following innovative research works:1.According to the characteristics of Asymmetric Double Mach-Zehnder optical fiber sensing technology,that the combination of double narrowband light source and dual DWDM optical fiber filter can effectively suppress backscattered light and filter the backscattered noise,it is theoretically calculated that the maximum sensing monitoring distance of the disturbance sensor can be greater than 120 km.The endpoint detection method based on the short time Fourier transform(STFT)and the fast localization algorithm based on approximate derivatives to extract the disturbance signal characteristics are proposed,and the above two methods could effectively improve the localization accuracy and detection efficiency.2.Based on disturbance events is mainly affected by signal visibility,signal-to-noise ratio and non-stationary characteristics of disturbance sensing events,we propose a multi-dimensional event feature extraction algorithm combining variational mode decomposition,sample entropy and short-term zero-crossing rate.And it is feature extraction and classification recognition accuracy can reach above 98%.3.We carried out instrumentalized design of software and hardware system based on Aymmetric Double Mach-Zehnder distributed optical fiber perimeter alarm system.In hardware design,it is divided into light source module,sensor module,detection module,data acquisition module and power supply module to select and design,the polarization controller based on FPGA is designed to realize the hardware polarization control of the system,and then complete the design and assembly of sensor host.In the design of the system software,it is divided into two modules: basic function and signal processing,then formed a complete function of optical fiber perimeter alarm system.In combination with the actual engineering environment,research on composite monitoring technology has realized the infrared video monitoring system with the Aymmetric Double Mach-Zehnder distributed optical fiber perimeter alarm system linkage and achieved good results.Carry out train interference modal performance study of the Aymmetric Double Mach-Zehnder distributed optical fiber perimeter alarm system,through the optimization design,the original system is optimized and improved into a perimeter alarm system combining the positioning type and the defense type.