Free-space optical (FSO) communication provides wireless optical connectivity with high data rates and low-cost implementation; however, its performance is strongly influenced by the power attenuation due to the infrequent adverse weather conditions. This article proposes a novel highly sensitive dual-mode receiver comprising an array of single-photon avalanche diodes (SPADs) and a PIN photodiode (PD) to enhance the availability of FSO links. In adverse weather conditions, the receiver operates in the SPAD-mode; whereas, in the clear weather conditions, the receiver works in the PD-mode. A hybrid receiver controller is employed in the proposed receiver to adaptively control the switching process based on the received light levels. The adaptive controller also adjusts the incident photon rate of the SPAD array using a variable optical attenuator (VOA) to optimize the performance of the SPAD unit. Our extensive performance analysis illustrates the superior achievable data rates of the proposed receiver under various weather conditions compared to the traditional FSO receivers with either PD or SPAD array.

中文翻译：

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混合SPAD / PD接收机，用于可靠的自由空间光通信

自由空间光（FSO）通信以高数据速率和低成本实现提供无线光连接；然而，由于不常见的恶劣天气条件，其性能受到功率衰减的强烈影响。本文提出了一种新颖的高灵敏度双模接收器，该接收器包括一个单光子雪崩二极管（SPAD）和一个PIN光电二极管（PD）阵列，以增强FSO链路的可用性。在恶劣的天气条件下，接收机以SPAD模式工作；而在晴朗的天气条件下，接收器以PD模式工作。在所提出的接收器中采用了混合接收器控制器，以基于接收到的光水平来自适应地控制切换过程。自适应控制器还使用可变光衰减器（VOA）来调整SPAD阵列的入射光子速率，以优化SPAD单元的性能。我们广泛的性能分析表明，与具有PD或SPAD阵列的传统FSO接收器相比，该提议的接收器在各种天气条件下均可实现更高的数据传输率。