自由空间光通信中相干圆偏振调制系统性能研究

自由空间光通信（FSO）具有高带宽、不需要铺设光纤、部署迅速、低功率损耗等优点，得到了广泛的关注。在Gamma-Gamma大气湍流信道下，分别考虑弱、中、强三种大气湍流强度，结合相位噪声，研究了相干探测的圆偏振调制系统的性能，推导出了误码率和中断概率的闭合表达式。在不同的大气湍流强度和相位噪声的情况下，仿真分析了相干探测的圆偏振调制系统的性能，并与直接探测系统的误码性能进行比较，结果表明，采用相干探测系统的误码性能优于直接探测系统。因此，在圆偏振调制系统中，采用相干探测方式可减小大气湍流的影响，大大降低了误码率，提高了系统的通信性能。

Study on performance of circle polarization modulation system with coherent detection in free space optical communication

Free space optical communication (FSO) has the advantages of high bandwidth, no need to lay fiber, low power loss, so it has attracted attention. In Gamma-Gamma atmospheric turbulence channel model, weak, medium and strong three atmospheric turbulence intensity were respectively considered, and combined with the phase noise, the performance of circular polarization modulation system with coherent detection was studied, and the closed form expression of the bit error rate(BER) and outage probability were derived. In the different atmospheric turbulence intensity and phase noise, the performance of the circular polarization modulation system with the coherent detection was simulated and analyzed. Compared with the error performance of the direct detection system, the results show that the error performance of the coherent detection system is better than that of the direct detection system. Therefore, in the circular polarization modulation system, employing the coherent detection method can reduce the effect of the atmospheric turbulence and greatly reduce the BER, and improve the performance of the communication system.