Research On The Performance Of The Free Space Optical Communication System With Pointing Errors Effect

Free space optical communication technology can effectively realize high speed rate and security communication,which has been the research hotspots in recent decades.Many countries and regions,such as USA,Europe,Japa n and China,have been successfully realized in-orbit satellite laser communication test by using different detection systems.The performance of free space optical communication links is affected by numerous factors.Pointing errors is the one of the most important factors.In the process of establishing the space optical communication links,the scan lost caused by pointing errors is obvious by using the narrow beacon.The communication system by using narrow beacon to scan field of uncertainty where the s atellite of the receiver is located.And pointing errors and improper selection of scanning parameters result in the scan lost,thus reducing the acquisition probability and increasing the scan time.In the process of free space optical communication,pointing errors at the transmitter causes the transverse deviation from the center of the received signal beam at the receiver,which decrease the bit error rate and increase the average fiber coupling efficiency.So far,the analysis of the pointing errors effect and scanning parameters on the acquisition probability and scan time has not been reported.Effects of pointing errors and atmospheric turbulence on fiber coupling efficiency for the space laser optical communication system has not been reported.In this paper,pointing errors effect on the acquisition probability and average scanning time of intersatellite communication links,bit error rate of horizontal laser communication system and fiber coupling efficiency of the free space optical communication system are systematically studied.In addition,the theoretical formulas of bit error rate and fiber coupling efficiency are verified by urban horizontal link experiments.The main research contents of this paper are divided into chapters as follows:1.The theoretical model of pointing errors effect on average scan time and acquisition probability for inter-satellite laser link is established.The calculation formula of average scan time and acquisition probability are deduced.The influence of factors,such as scan parameters,pointing errors and field of uncertainty,are given.By using Monto Carlo simulation,pointing error s effect on the acquisition probability of each times in the multi-scan are also given.2.The Beckmann probability density distribution model of pointing errors and the BER of the horizontal links with pointing errors are given.When the pointing errors satisfy Beckmann distribution,the model of misalignment distribution in the receiver and channal gain are established.The analytical expressions of BER of horizontal laser links is also given.According to the analytical expressions,the variation of the BER in the horizontal links with pointing errors and atmospheric turbulence is discussed.3.The theoretical model of average optical fiber coup ling in horizontal links is established.The fiber coupling efficiency of the horizontal lins and downlinks with pointing errors is given.Based on pointing errors of Beckmann distribution,the variation of the fiber coupling efficiency with the factors,such as pointing errors and atmospheric,is discussed.4.Considering pointing errors effect,an urban horizontal link experiment of 11.16 km was conducted to verify the theory,such as channel gain,BER,fiber coupling efficiency.In the experiment,measurement of the receiver intensity is conducted to verify theory,such as channel gain,BER,fiber coupling efficiency.In this paper,the effect of pointing errors on the free space optical communication link performance has been studied.It contributes a theoretical foundation for the pointing errors effect on the performance in free space optical communication system and the parameter o ptimization of an optical communication system.