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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 d Bm,此时可获得最佳平均载噪比,当本振光功率大于-11 d Bm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 d Bm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 (OFDM) technology based on coherent detection is one of the important solutions for high-speed optical communication technology in the future. Since the structure of coherent optical detection system is not easy to realize, the subcarrier heterodyne detection technique is adopted to detect subcarrier orthogonal frequency division multiplexing Use optical signals. The atmospheric turbulence channel system transmission model was established and the CNR and BER of the subcarriers were deduced. The closed-form expressions of the mean optical bit error rates (BERs) of the system were numerically analyzed. Influence, and verify through the simulation experiment. Experimental results show that, compared with direct detection, subcarrier heterodyne can further improve the average carrier to noise ratio and improve system error performance. When the received optical power is in the order of microwatts, the local oscillator optical power is about -11 d Bm, and the best average carrier to noise ratio is obtained. When the local optical power is greater than -11 d Bm, Increase the average carrier to noise ratio gradually decreased, the average bit error rate increased. Under the condition of weak turbulence, when the received optical power is greater than -17 d Bm, the average bit error rate is above 10-5, so the reliability of wireless optical communication system can be guaranteed.