一种基于OAM的FSO误码性能的理论分析方法

A Theoretical Analysis Method of OAM-Based FSO Error Performance

携带轨道角动量的涡旋光束在自由空间光通信信道中传输时,信道中的湍流介质会改变涡旋光束的传播特性,破坏波前螺旋结构,最终直接影响通信的稳定性和可靠性.针对现有实验研究在普适性方面的不足,本文选取基于相干光束合成技术的高功率涡旋光束阵列为研究光源,从理论角度出发,建立一套完备的体系架构,用以分析大气湍流引起的幅度和相位起伏对基于轨道角动量的自由空间光通信系统性能的影响.应用光学外差检测,对湍流条件下信噪比的随机分布进行详细的研究,并基于此得到多进制相移键控调制下符号错误概率的解析表达式,评估不同湍流信道参数、光源参数以及接收机参数对符号错误概率的影响.结果表明,增大阵列子光束束腰半径、阵列子光束个数,减小阵列环状半径,可以提高光束质量,优化系统性能.另外,较小的拓扑荷数、传播距离和湍流强度以及较大的接收孔径直径使得符号错误概率较低,对应的通信性能更佳.

When the vortex beam carrying orbital angular momentum(OAM)is transmitted in the free space optical communication(FSO)channel,the turbulent medium in which will change the propagation characteristics of the vortex beam,destroy the spiral structure of the wave-front,and ultimately directly affect the stability and reliability of communication.To make up the shortcomings of the previously experimental research in the generalization,a high-power vortex beam array based on coherent beam combining(CBC)technology is selected as the research light source,and a complete system architecture is established from a theoretical point of view to analyze the impact of the amplitude and phase fluctuations caused by atmospheric turbulence on the performance of OAM based FSO communication systems.Applying the optical heterodyne detection(OHD),the random distribution of signal-to-noise ratio(SNR)under turbulent conditions is studied in detail.Based on this,the analytical expression of symbol error probability(SEP)under the condition of Mary Phase-Shift Keying(MPSK)has been derived,and the influence of different turbulence channel parameters,beam parameters and receiver parameters on SEP has been investigated.The results suggest that increasing the beam waist radius of the array subbeams and the number of the array sub-beams,and reducing the ring radius of the array can improve the beam quality and optimize the system performance.In addition,the smaller topological charge,propagation distance and turbulence intensity,and larger receiver aperture diameter can make the symbol error probability lower and the corresponding communication performance better.