大气信道中，信道衰落以及天线间距的限制导致无线光多输入多输出(MIMO)系统的各光束间存在一定的相关性，这种相关性严重影响无线光通信系统的性能。基于脉冲位置调制(PPM)建立了相关信道下无线光MIMO系统的信道模型，并采用Wilkinson方法推导出对数正态衰落时无线光MIMO系统的平均信道容量。模拟结果表明：空间相关性的存在降低了系统的平均信道容量，而且随着总能量的增大，相关性带来的容量损失也增大。在完全相关信道中，发送端相关对信道容量产生的影响比接收端相关的影响更为严重。

tIn the atmospheric channel, the spatial correlation among the beams of wireless optical multiple input multiple output (MIMO) system caused by the antenna spacing and the channel fading can seriously affect the wireless optical communication system performance. We proposed a channel model for the correlative wireless optical MIMO channel based on the pulse position modulation (PPM), and the average channel capacity in lognormal fading channel is derived by using the Wilkinson method. The simulation results indicate that the average channel capacity is decreased due to the spatial correlation, and the effect is enhanced with the growth of the total energy. In addition, in a completely correlative channel, the impact of transmitter correlation on the channel capacity is more obvious than that of the receiver correlation.