中文摘要：

给出了一种采用全光放大转发中继的双跳自由空间光（FSO）通信系统的基本结构,假定采用副载波强度调制,考虑背景噪声对系统性能的影响,导出了在Gamma-Gamma大气湍流复合信道下系统的误码率（BER）和中断概率闭合表达式。通过仿真对比分析了采用全光放大转发中继的FSO系统与电放大转发中继FSO的中断概率及误码率,并且分析了大气湍流、信噪比（SNR）等参数对全光中继系统性能的影响。结果表明,采用全光放大转发中继的系统性能优于电放大转发中继;可以通过优化波束宽度使得全光中继的系统性能达到最优。

英文摘要：

In this paper,we present the fundamental structure of all-optical dual-hop free space optical （FSO） communication systems,which adopts amplify-and-forward relaying. Assuming that the systems adopt subcarrier intensity modulation,we derive the novel closed-form expressions for the outage proba- bility and bit-error rate （BER） of all-optical dual-hop FSO communication systems under Gamma-Gam- ma atmospheric turbulence and the composite fading channel model, which take into account the effects of background noise. Then we compare the outage probability of dual-hop FSO communication systems which adopt all-optical amplify-and-forward relaying with the dual-hop FSO communication systems which adopt electrical amplify-and-forward relaying. We also investigate how the performance of all-opti- cal relaying flee space optical communication systems is affected by the parameters, such as atmospheric turbulence and signal-to-noise ratio （SNR）. The simulation results show that the systems with all-opti- cal amplify-and-forward relaying is superior to the systems with electrical amplify-and-forward relaying. We also can draw that can be achieved by optimizing the beamwidth the minimum BER of all-optical du- al-hop relaying systems for a given average transmitted optical power.