Zhu Yixiao, Xu Yicheng, Hu Weisheng, Zhuge Qunbi
Opt Lett. 2022 Aug 1;47(15):3836-3839. doi: 10.1364/OL.462631.
Efficient signal-to-noise ratio (SNR) and spectral efficiency (SE) trade-off can offer fundamental guiding law for future large-capacity and high-fidelity mobile fronthaul. In this Letter, we propose and experimentally demonstrate a cascaded digital-analog radio-over-fiber (CDA-RoF) scheme, which transmits digitized and analog segments using time-division-multiplexing aggregation. Specifically, multiple digital parts generated by a rounding function describe the main features of the original waveform, while the residual error is magnified and delivered as analog RoF with SE advantage. Based on a 20-GHz O-band directly modulated laser (DML), an SNR enhancement of >10 dB is observed for each extra bandwidth. Up to 70.4-dB SNR is also achieved for a 3.5-GHz 1048576-ary quadrature amplitude modulation (1048576-QAM) signal after 20-km standard single-mode fiber (SSMF) transmission.
高效的信噪比（SNR）和频谱效率（SE）权衡可为未来大容量、高保真移动前传提供基本指导规律。在本信函中，我们提出并通过实验演示了一种级联数字 - 模拟光纤无线电（CDA - RoF）方案，该方案使用时分复用聚合来传输数字化和模拟段。具体而言，由舍入函数生成的多个数字部分描述了原始波形的主要特征，而残余误差则被放大并作为具有SE优势的模拟RoF进行传输。基于20 GHz O波段直接调制激光器（DML），每增加一个带宽，可观察到SNR增强超过10 dB。在20 km标准单模光纤（SSMF）传输后，对于3.5 GHz 1048576进制正交幅度调制（1048576 - QAM）信号，也实现了高达70.4 dB的SNR。
