提出了基于动态门限的幅度调制空间相干光通信(IM/CD)系统。与传统的幅度调制/直接检测(IM/DD)光通信系统相比, 我们提出的系统无需瞬时信道状态信息(CSI)和大气湍流模型的概率密度函数(pdf)就可以实现对信号的高精度检测, 与此同时该系统能通过提高本振激光器的功率来获取更好的误码率(BER)性能。此外, 本文还推导了该系统平均误码率的表达式。仿真实验表明, 当本振激光器和发射信号的归一化幅度为1、平均误码率为10-9时, 该系统在归一化大气闪烁标准差σ=0.25、归一化相位噪声标准差σφ=0.07的对数正态湍流信道条件下, 与理想的自适应探测门限光通信系统相比, 其信噪比性能损失仅为1.4 dB。

Free-space coherent optical communication system using irradiance modulation(IM/CD) with dynamic detection threshold is proposed. Compared with traditional irradiance modulation and direct detection(IM/DD) systems, the system we proposed can detect the signal without requiring the knowledge of instantaneous channel state information(CSI) and the probability density function(pdf) of the turbulence model and achieve better average bit error rate(BER) just by only improving the LO power. Analytical expressions are derived for the average bit error rate of the system. Numerical studies show that the proposed system can achieve comparable performance to the idealized adaptive detection system, with a signal-to-noise ratio performance loss of only 1.4 dB at a BER of 10-9 for a lognormal turbulence channel with σ=0.25 and phase noise with σφ=0.07 when the local oscillator(LO) amplitude and transmitting amplitude are assumed to be unity.