Research On The Asymmetric Dual Mach-Zehnder Interferometry Based Distributed Disturbance Sensing Technology

Due to the the advantages of wide frequency response range,high sensitivity and simple structure,distributed fiber disturbance sensor has broad application prospects in the field of structure health monitoring,perimeter and pipeline security,the Internet of Things,and so on.Based on the analysis of different kinds of distributed fiber disturbance sensors,a novel one is proposed with the design of asymmetric dual Mach-Zehnder interferometry(ADMZI).The ADMZI can significantly reduce the influence of Rayleigh backscattering noise,which will seriously deteriorate the signal noise ratio(SNR)and can achieve distributed fiber disturbance sensing at long range.This dissertation introduces the working principle of the ADMZI at first,then analyses the factors of visibility and positioning accuracy.Based on these,the dissertation proposes a visibility compensation method and a high-accuracy poisoning method.On the basis of various requirements,it also studies the method of detection and classification disturbance,and finishes the software design of the sensor.These works propel the engineering steps very well.The main contents are as follows:1.Based on the analysis of SNR deterioration caused by the Rayleigh backscattering noise,we propose a Rayleigh backscattering noise restrain structure using two light sources and proper fiber filters.And then we combine this structure and dual Mach-Zehnder fiber disturbance sensor(DMZI)and create the AMDZI.The ADMZI can achieve higher SNR than DMZI,which guarantees a longer sensing range.2.By the analysis of the factor of visibility,we find that the gain-band product and the polarization effect both deteriorate the visibility.To solve this problem,we propose a gain compensation method and a polarization compensation method to keep the visibility stable.The two methods work well and benefit signal processing function in the subsequent steps.3.By the study of the working principle of the ADMZI,we find that the asymmetry of the two channel signals will seriously deteriorate the positioning accuracy.Based on this,we propose an effective positioning process and a fast positioning algorithm for different applications.4.We design the sensing system and processing software with the thoughts of modularization,and finish the prototype of the sensor.After this,we use this sensor on the application of railway perimeter security and pipeline security.By the study of the applications before,we improve the optical structure and the signal processing method appropriately,which makes the sensor suitable for the practical applications.