研究了一种光功率效率高的非对称限幅光正交频分复用(OFDM)调制技术，通过对信号的非对称削减，将OFDM调制技术运用到光通信领域。将这种非对称限幅光OFDM技术运用到大气激光通信系统中，分析了采用非对称限幅光OFDM技术大气激光通信系统在大气湍流信道下的性能。在此基础上，将低密度奇偶校验(LDPC)码和置信传播迭代译码算法应用到大气激光通信系统中，并结合非对称限幅光OFDM强度调制方案，在大气湍流信道中进行了仿真。仿真结果表明，LDPC码具有优越的纠错能力并获得了较大的编码增益，该方案可以满足大气激光通信系统的需要。

The asymmetrically clipped optical orthogonal frequency division multiplexing (OFDM) modulation technique is investigated. It is a new technique for using OFDM in optical system. Asymmetrically clipped OFDM is derived from a bipolar OFDM waveform by setting the negative values to zero. The asymmetrically clipped OFDM technique is applied to atmospheric communication system in this paper, and the performance of atmospheric communication system using asymmetrically clipped OFDM technique through atmospheric turbulence channels is analyzed. On this basis, the low density parity check (LDPC) codes and belief propagation (BP) iterative decoding algorithm are applied into the atmospheric communication system, and it is simulated in the atmospheric turbulence channel with combination of asymmetrically clipped optical OFDM intensity modulation. The simulation results show that LDPC codes have excellent error correction capabilities and access to a larger coding gain,and the above scheme can satisfy the need of atmospheric laser communication system.