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大气湍流是自由空间光通信链路系统的主要限制因素。大气湍流造成光束的强度闪烁和相位起伏。因此,基于MZI-DPSK调制,考虑大、小湍流尺度引起的强度闪烁和相位噪声对误码率的影响且强度闪烁满足逆高斯分布和相位波动满足高斯分布。利用分布式天线阵接收技术,研究了大气湍流下自由空间光通信链路的误码率性能,推导了在内外尺度下,分布式天线阵接收的误码率关于相位误差的函数表达式。为了提高误码率的性能,天线阵接收采用了最大比合并技术。仿真结果得出相位误差对误码率的影响很大;内外尺度对误码率的影响可以忽略不计。采用天线阵接收可以降低系统的误码率,提高通信系统的性能,且得出天线阵接收的最佳子天线个数。
Atmospheric turbulence is a major limiting factor in the free-space optical communications link system. Atmospheric turbulence caused by the intensity of the light beam flashing and phase fluctuations. Therefore, based on the MZI-DPSK modulation, we consider the effects of intensity flicker and phase noise on the bit error rate caused by large and small turbulence scales and the intensity flicker satisfies the Gaussian distribution and the phase fluctuation to satisfy the Gaussian distribution. Using the distributed antenna array receiving technique, the bit error rate performance of the free space optical communication link under atmospheric turbulence is studied, and the function error expression of the BER for the distributed antenna array is deduced. In order to improve the performance of the bit error rate, the antenna array adopts the maximum ratio combining technique. The simulation results show that the phase error has a great influence on the bit error rate. The impact of the internal and external scales on the bit error rate can be neglected. The use of antenna array to receive can reduce the bit error rate of the system and improve the performance of the communication system, and get the best sub-antenna number received by the antenna array.