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结合正交频分复用(OFDM)技术和相干探测的优势,研究了相干OFDM自由空间光通信(FSO)系统的误码性能,考虑了OFDM映射方式以及映射阶数对系统误码性能的影响。在GammaGamma大气湍流信道下,分别从平均信噪比和所需平均接受光功率的角度考虑了系统在弱、中和强湍流三种情况下的误码性能。在此基础上,推导了系统误符号率的闭合表达式。仿真结果表明,相干探测下OFDM FSO系统可以较好地克服大气湍流效应,在弱、中湍流情况下,QAM映射方式下系统的误码性能明显优于PSK方式,在强湍流下这种优势不明显,此外随着映射阶数的增加,系统误符号率增加,因此在实际应用中可以通过降低映射阶数来提高系统误码性能。
Combining the advantages of Orthogonal Frequency Division Multiplexing (OFDM) and coherent detection, the BER performance of coherent OFDM free space optical communication (FSO) system is studied. The effect of OFDM mapping mode and mapping order on system error performance . Under the GammaGamma atmospheric turbulence channel, the BER performance of the system in three cases of weak, moderate and strong turbulence are respectively considered from the average signal-to-noise ratio and the required average received optical power. Based on this, the closed expression of system symbol error rate is deduced. The simulation results show that the OFDM FSO system can better overcome the atmospheric turbulence effect under coherent detection. Under weak and medium turbulence conditions, the error performance of the system under QAM mapping is better than that of PSK. Under strong turbulence, this advantage is not Obviously, in addition, as the order of the mapping increases, the system error symbol rate increases, so in practical applications, the system error performance can be improved by reducing the mapping order.