Abstract This paper proposes a wavelength diversity decode-and-forward (DF) serial relay orthogonal frequency division multiplexing (OFDM) free-space optical (FSO) communication system. The proposed system performance is evaluated by the quadrature phase-shift keying (QPSK) as an OFDM signal subcarrier mapping method, considering the maximum ratio combining (MRC) and equal gain combining (EGC) schemes, over exponentiated Weibull (EW) channels. The Monte Carlo (MC) method is used to simulate the system performance. The closed-form expressions of outage probability and average symbol error rate (SER) are also derived considering the joint effect of atmospheric turbulence, path loss, and pointing errors. In addition, the effects of the number of operating wavelength, receiving aperture diameter, number of relay hops, and link length between relays on the outage performance of an FSO communication system, and the effect of the MRC and EGC schemes the average SER are analyzed through simulations. The MC simulations verify the correctness of the numerical results. The results show that the proposed system can concurrently expand the communication range and improve system performance.

中文翻译：

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指数Weibull信道上波长分集串行中继OFDM FSO系统的性能研究

摘要 本文提出了一种波长分集解码转发（DF）串行中继正交频分复用（OFDM）自由空间光（FSO）通信系统。所提出的系统性能通过正交相移键控 (QPSK) 作为 OFDM 信号副载波映射方法进行评估，考虑最大比合并 (MRC) 和等增益合并 (EGC) 方案，在取幂威布尔 (EW) 信道上。Monte Carlo (MC) 方法用于模拟系统性能。考虑到大气湍流、路径损耗和指向误差的共同影响，还推导出了中断概率和平均误码率（SER）的闭式表达式。此外，工作波长数、接收孔径直径、中继跳数、通过仿真分析了中继之间的链路长度对 FSO 通信系统中断性能的影响，以及 MRC 和 EGC 方案对平均 SER 的影响。MC 模拟验证了数值结果的正确性。结果表明，所提出的系统可以同时扩展通信范围并提高系统性能。