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在自由空间激光通信(FSO)系统中,瞄准误差和大气湍流严重影响系统通信链路,是链路性能恶化的两大主要因素。通过对联合信道的理论分析,建立了信道模型,并利用Meijer G函数推导出了直接探测系统和相干探测系统平均信道容量的表达式。通过在Matlab中的仿真结果可知,在给定瞄准误差和大气湍流的条件下,信号光的光束束散角并非越小越好,而是存在最优束散角,该束散角不仅可以保证系统性能良好,而且使得发射系统功率取得最小值,并且采用相干探测系统可以抑制大气湍流对系统的影响,有效提高系统的性能。
In free space laser communications (FSO) systems, aiming errors and atmospheric turbulence severely impact the system communications link, which are two major contributors to link performance degradation. Through the theoretical analysis of the joint channel, the channel model is established, and the expression of the average channel capacity of the direct detection system and the coherent detection system is deduced by Meijer G function. According to the simulation results in Matlab, we can see that given the aiming error and atmospheric turbulence, the beam divergence of signal light is not as small as possible, but there is an optimal beam divergence angle, which not only can guarantee The system performance is good, and the power of the transmitting system is minimized, and using the coherent detection system can restrain the influence of the atmospheric turbulence on the system and effectively improve the system performance.