大气湍流和瞄准误差下差分相移键控光通信系统的性能分析

Analysis of Differential Phase Shift Keying in Free-Space Optical Communication System over Atmospheric Turbulence and Pointing Errors

详细研究了Gamma-Gamma湍流信道大气闪烁、信道衰落及瞄准误差对差分相移键控(DPSK)相干光通信系统误码性能、信道容量和中断概率等指标的影响。自由空间光通信(FSO)系统采用基于马赫-曾德尔调制器(MZM)和马赫-曾德尔干涉仪(MZI)的DPSK调制/解调结构,通过广义超几何方法分析推导出有关平均误码率、平均信道容量和中断概率的闭合表达式并简化分析。在Matlab平台下进行模拟仿真,实验结果表明,系统的平均误码率和平均信道容量随湍流程度的增强而减弱;信道容量的提升可以通过增加带宽或减小抖动方差实现;当瞄准误差过大时导致中断概率增大,严重影响系统的通信性能。

Under Gamma-Gamma atmospheric turbulence, the influence of atmospheric scintillation, channel loss and pointing error on the performance of differential phase shift keying（DPSK） coherent optical communication system such as the bit error rate（BER）, channel capacity and outage probability is studied in detail. Free space optical communication（FSO） system is based on the Mach- Zehnder modulator（MZM） and Mach- Zehnder interferometer（MZI） DPSK modulation/demodulation structure. The closed-form expression of average BER,average channel capacity and interruption probability is derived by the generalized hypergeometric method and the simplified analysis. The simulation is taken place under the Matlab platform. Numerical results show that the average BER and channel capacity are decreased with the atmospheric turbulence increased, the channel capacity can be promoted by increased the bandwidth or reduced the jitter variance, and the communication performance of the system is seriously affected by the increasing outage probability owing to the overlarge pointing error.