Free space optical (FSO) communication has gained significant popularity in recent years due to large bandwidth, license‐free spectrum, high data rates, less power consumption, and low mass requirements. However, system performance strongly depends on atmospheric conditions and ambient noise. In this letter, the duobinary modulation technique is applied and the system performance is investigated in the presence of ambient noise. The system is evaluated on the basis of Q‐factor, eye diagram, input power, transmission distance, and bit error rate. A significant improvement is observed in the presence of noise while using duobinary modulation. This study exploits extensive simulations to investigate the performance of the system. All simulations are performed for a single link of FSO communication network having a data rate of 40 Gbps in the Optisystem simulator and ambient noise is created using LEDs. After the exhaustive set of simulations, a significant improvement in transmission length is observed. It is also observed that at low input power, doubinary modulation provides better results when compared with on‐off keying (OOK) format. Scintillation effect has also be observed for doubinary modulation and compared with OOK modulation format. It is concluded that doubinary modulation provides better results in the presence of low and moderate scintillation.

中文翻译：

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在40 Gbps自由空间光信道中使用双二进制调制，在存在环境噪声和闪烁效应的情况下改善了传输长度

近年来，由于大带宽，免许可证频谱，高数据速率，更少的功耗和较低的质量要求，自由空间光（FSO）通信已获得了广泛的普及。但是，系统性能在很大程度上取决于大气条件和环境噪声。在这封信中，应用了双二进制调制技术，并在存在环境噪声的情况下研究了系统性能。根据Q因子，眼图，输入功率，传输距离和误码率对系统进行评估。使用双二进制调制时，在存在噪声的情况下观察到了显着的改进。这项研究利用广泛的仿真来研究系统的性能。在Optisystem仿真器中，对数据速率为40 Gbps的FSO通信网络的单链路执行所有仿真，并使用LED产生环境噪声。经过详尽的模拟后，可以观察到传输长度的显着改善。还可以观察到，与开关键控（OOK）格式相比，在低输入功率下，二进制调制可提供更好的结果。还观察到了双二进制调制的闪烁效果，并与OOK调制格式进行了比较。结论是，在低闪烁和中闪烁的情况下，双二进制调制可提供更好的结果。与开关键控（OOK）格式相比，双二进制调制可提供更好的结果。还观察到了双二进制调制的闪烁效果，并与OOK调制格式进行了比较。结论是，在低闪烁和中闪烁的情况下，双二进制调制可提供更好的结果。与开关键控（OOK）格式相比，双二进制调制可提供更好的结果。还观察到了双二进制调制的闪烁效果，并与OOK调制格式进行了比较。结论是，在低闪烁和中闪烁的情况下，双二进制调制可提供更好的结果。