All-digital radio-over-fiber (RoF) transmission has attracted a significant amount of interest in digital-centric systems or centralized networks because it greatly simplifies the front-end hardware by using digital processing. The sigma-delta modulator (SDM)-based all-digital RoF approach pushes the digital signal processing as far as possible into the transmit chain. We present a real-time 100-GS/s fourth-order single-bit SDM for all-digital RoF transmission in the high-frequency band without the aid of analog/optical up-conversion. This is the fastest sigma-delta modulator reported and this is also the first real-time demonstration of sigma-delta-modulated RoF in the frequency band above 24 GHz. 4.68 Gb/s (2.34 Gb/s) 64-QAM is transported over 10-km standard single-mode fiber in the C-band with 6.46$\text{}\%$ (4.73$\%$) error vector magnitude and 3.13 Gb/s 256-QAM can be even received in an optical back-to-back configuration. The carrier frequency can be digitally tuned at run-time, covering a wide frequency range from 22.75 to 27.5 GHz. Besides, this high-speed sigma-delta modulator introduces less than 1 μs latency in the transmit chain. Its all-digital nature enables network virtualization, making the transmitter compatible with different existing standards. The prominent performance corroborates the strong competitiveness of this SDM-based RoF approach in high-frequency RoF 5G communication.

中文翻译：

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用于全数字光纤传输的实时 100-GS/s Sigma-Delta 调制器

全数字光纤无线电 (RoF) 传输在以数字为中心的系统或集中式网络中引起了极大的兴趣，因为它通过使用数字处理极大地简化了前端硬件。基于 Sigma-Delta 调制器 (SDM) 的全数字 RoF 方法将数字信号处理尽可能地推进到发射链中。我们提出了一种实时 100-GS/s 四阶单比特 SDM，用于高频段全数字 RoF 传输，无需模拟/光学上变频的帮助。这是所报道的最快的 Sigma-Delta 调制器，这也是 24 GHz 以上频段 Sigma-Delta 调制 RoF 的首次实时演示。4.68 Gb/s (2.34 Gb/s) 64-QAM 在 6.46$\text{}\%$ (4. 73$\%$) 误差矢量幅度和 3.13 Gb/s 256-QAM 甚至可以在光背对背配置中接收。载波频率可在运行时进行数字调谐，覆盖 22.75 至 27.5 GHz 的宽频率范围。此外，这种高速 Sigma-Delta 调制器在传输链中引入了不到 1 μs 的延迟。其全数字特性支持网络虚拟化，使发射器兼容不同的现有标准。突出的性能证实了这种基于SDM的RoF方法在高频RoF 5G通信中的强大竞争力。这种高速 Sigma-Delta 调制器在传输链中引入了不到 1 μs 的延迟。其全数字特性支持网络虚拟化，使发射器兼容不同的现有标准。突出的性能证实了这种基于SDM的RoF方法在高频RoF 5G通信中的强大竞争力。这种高速 Sigma-Delta 调制器在传输链中引入了不到 1 μs 的延迟。其全数字特性支持网络虚拟化，使发射器兼容不同的现有标准。突出的性能证实了这种基于SDM的RoF方法在高频RoF 5G通信中的强大竞争力。