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Clone-comb-enabled high-capacity digital-analogue fronthaul with high-order modulation formats


Access to the internet by mobile terminals relies on the transmission of information from the optical fibre backbone to wireless networks. Fronthaul, as the last mile of fibre-wireless convergence, determines the overall transmission performance in terms of capacity and fidelity. Orders-of-magnitude increases in both bandwidth and signal-to-noise ratio (SNR) are urgently desired to cope with the large growth in wireless traffic. Here we demonstrate a self-homodyne digital-analogue radio-over-fibre fronthaul using cloned optical frequency combs that meets these needs. The approach simultaneously supports an unprecedented 14.1 Tb s−1 common public radio interface equivalent data rate and a 1,024 quadrature-amplitude-modulated format. The clone-comb configuration, which possesses the properties of frequency and phase locking, is the key to enabling a high-performance coherent digital-analogue radio-over-fibre system. Besides exploiting the quadruple capacity for a single channel thanks to coherent detection, the clone-comb approach can also provide multiple parallel channels concurrently, boosting the overall data throughput. We further demonstrate the potential of the technique, showing its ability to transmit 65,536 quadrature-amplitude-modulated signals and a data rate of 32.8 Tb s−1. Our architecture is promising for fibre-based and free-space optical fronthaul, bringing full-band and coherent-lite access networks into reach.

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Fig. 1: Concept and architecture of the clone-comb-enabled DA-RoF fronthaul.
Fig. 2: Implementation scheme and DA-RoF principle.
Fig. 3: Clone-comb performance and DA-RoF parameters.
Fig. 4: Experimental results for 12-channel 1,024- and 256-QAM wireless signals.
Fig. 5: DA-RoF format extension and state of the art.
Fig. 6: Capacity boosting with spectral-broadened clone comb.

Data availability

The data that support the plots within this paper and other findings of this study are available on Zenodo ( All other data used in this study are available from the corresponding authors on reasonable request.

Code availability

The codes that support the findings of this study are available from the corresponding authors on reasonable request.


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This work is funded by National Key R&D Program of China (grant no. 2019YFB2203702 to X.X., 2022YFB2903500 to Q.Z. and 2018YFB2201704 to Weiwei Hu) by National Natural Science Foundation of China (grant no. 62071010 to X.X. and 62271305 to Weisheng Hu).

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Authors and Affiliations



C.Z., Y.Z. and X.X. jointly designed the experimental set-up. Y.Z. provided the initial basis for DA-RoF technique and digital processing methods. C.Z., B.H. and X.X. provided the initial basis for comb clone technique. C.Z. performed the experiment and analysed the results. C.Z., Y.Z., J.L. and X.X. wrote the manuscript. All co-authors contributed by providing their valuable feedback and comments. X.X. supervised the work.

Corresponding authors

Correspondence to Yixiao Zhu or Xiaopeng Xie.

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Nature Photonics thanks Giovanni Tartarini, Yongsheng Gao, Carmen Vazquez and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Zhang, C., Zhu, Y., He, B. et al. Clone-comb-enabled high-capacity digital-analogue fronthaul with high-order modulation formats. Nat. Photon. 17, 1000–1008 (2023).

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