基于相干检测的正交频分复用技术是未来高速光通信技术的重要解决方案之一，由于相干光检测系统结构复杂不易实现，因此采用副载波外差检测技术检测副载波正交频分复用光信号。建立了大气湍流信道系统传输模型，推导了子载波平均载噪比(CNR)和平均误比特率(BER)的闭合表达式，数值分析了本振光功率和调制系数对系统平均误比特率的影响，并通过仿真实验进行验证。实验结果表明，与直接检测相比，副载波外差可以进一步提高平均载噪比，提升系统误码性能。当接收光功率为微瓦量级时，本振光功率约为-11 dBm，此时可获得最佳平均载噪比，当本振光功率大于-11 dBm 时，随本振光功率增加平均载噪比逐渐降低，平均误比特率升高。弱湍流条件下，当接收光功率大于-17 dBm 时，平均误比特率为10-5以上，此时可以保证无线光通信系统的可靠性。

Orthogonal frequency division multiplexing based on coherent detection is considered as one of significant solutions for future high-speed optical communication technology. However, because the structure of coherent optical detection system is complex and hard to implement, the subcarrier heterodyne detection technology is utilized to detect the subcarrier orthogonal frequency division multiplexed optical signal. The transmission system of atmospheric turbulence channel is established. The close form expressions for subcarrier average carrier-tonoise ratio (CNR) and average bit error rate (BER) are derived. The effects of opticallocal oscillator power and modulation index on average bit error rate of the system are numerically analyzed and verified by simulation experiment. The results show that subcarrier heterodyne detection is able to further improve the average CNR and therefore to obtain a better BER performance of the system compared to direct detection. When the order of the received optical is microwatts and the optical local oscillator power is close to -11 dBm, the best value of average CNR would be achieved. When the local oscillator power is larger than -11 dBm, the average CNR gradually reduces and the average bit error rate raises with the increase of optical local oscillator power. When the received optical power is larger than - 17 dBm and the average BER is greater than 10- 5, the reliability of wireless optical communication system under weak turbulence would be ensured.