Research On Polarization Mode Dispersion Of Electrical Power Overhead Optical Cable Communication System

With the comprehensive construction of strong smart grid,the power system gradually moves towards modernization and intelligent development.In addition to traditional power transmission,the power grid also undertakes a richer mission,becoming an integrated support platform of the energy,power and information service system.The rapid development of power big data has raised higher requirements for power technology and corresponding communication infrastructure.As a kind of special optical cable of electric power communication systems,overhead optical cable is widely used because of its high reliability and long lifespan.Overhead optical cables are suspended in the air,and the environment they are installed in is relatively harsh.As the transmission speed,bandwidth,and distance of the electric power communication systems continue to increase,polarization mode dispersion(PMD)has gradually become a key limiting factor for the transmission performance of overhead optical cables.Therefore,by studying and analyzing polarization mode dispersion of electric power overhead optical cables communication systems,real-time monitoring of the transmission quality of communication links can be achieved.This research can not only provide practical guidance for the installation and operation of existing cables,but also promote the upgrade and maintenance of old lines in the electric power overhead optical cable system,which has important research significance.This thesis focuses on the research for polarization mode dispersion in the electric power overhead optical cables communication system and explains the mechanisms of polarization mode dispersion in overhead optical cables under different scenarios.Moreover,this thesis constructs a modular experimental PMD monitoring system,and demonstrates its application on actual operating optical fiber composite overhead ground wire(OPGW).Finally,based on the PMD monitoring system,an optimization scheme of PMD monitoring system based on particle swarm optimization(PSO)is proposed and implemented.The main work and achievements of this thesis are as follows:(1)Based on the comparative analysis of various PMD measuring methods,The fixed analyzer(FA)method,due to its high measurement accuracy,simple experimental equipment,and ease of operation,is adopted as the basic experimental measurement scheme.Based on the market research of experimental devices,each module of PMD monitoring scheme is designed and selected.According to the different characteristics of the optical fiber to be measured,different data processing methods are used to analyze the measured data.For weak mode-coupling fibers,the PMD is measured by the precise extremum counting method,and for random mode-coupling fibers,PMD is measured by the Fourier transform method.(2)A modular PMD monitoring experimental system is built to measure optical fibers of different lengths and types,and the measurement results are compared with the commercial measuring instrument EXFO FTB-400,The measurement error of the two measurement methods is only 4.57%,which proves the effectiveness and accuracy of the proposed measurement scheme.The PMD monitoring scheme is deployed and measured for the ultra-long span of OPGW.According to the measured results,the statistical characteristics of PMD obey Maxwell distribution and conform to the theoretical model of polarization mode dispersion.Combining the measurement results with weather data,the influence of weather factors on the PMD in OPGW is preliminarily explored.(3)This thesis analyzes the influence of the polarization controller in the proposed PMD monitoring scheme on the measurement results.Moreover,the thesis expounds the difficulty in determining the rotation angle of the polarization controller in the experiment.Then,an optimization scheme of PMD monitoring system based on FA-PSO is proposed.In the research,combined with the practical application of the polarization controller,the fitness function and main parameters of the PSO algorithm are designed,and the position and velocity of particles are initialized.In the optimization scheme,the three rotation angles of the polarization controller are used as the basic particles of the algorithm,and the peak to valley ratio(PVR)corresponding to every particle is used as the fitness of the objective function of the PSO algorithm.Finally,the optimization scheme of PMD monitoring system based on FA-PSO is implemented and verified.Experimental results show that the proposed algorithm can converge quickly within 10 iterations,realize the optimal angle positioning of the polarization controller,and greatly save the test response time of the system.