Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Article
  • Published:

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

Nature Photonics volume 17, pages 1000–1008 (2023)Cite this article

Subjects

Abstract

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.

This is a preview of subscription content, access via your institution

Access options

Buy this article

  • Purchase on Springer Link
  • Instant access to full article PDF
Buy now

Prices may be subject to local taxes which are calculated during checkout

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.

Similar content being viewed by others

Data availability

The data that support the plots within this paper and other findings of this study are available on Zenodo (https://doi.org/10.5281/zenodo.8062271). 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.

References

  1. Peng, M., Wang, C., Lau, V. & Poor, H. V. Fronthaul-constrained cloud radio access networks: insights and challenges. IEEE Wireless Commun. 22, 152–160 (2015).

    Article  Google Scholar 

  2. Liu, X. Enabling optical network technologies for 5G and beyond. J. Lightwave Technol. 40, 358–367 (2022).

    Article  ADS  Google Scholar 

  3. Pizzinat, A., Chanclou, P., Saliou, F. & Diallo, T. Things you should know about fronthaul. J. Lightwave Technol. 33, 1077–1083 (2015).

    Article  ADS  Google Scholar 

  4. CPRI Specification, V6.1. Common Public Radio Interface (CPRI); Interface Specification (CPRI, 2013).

  5. eCPRI Specification, V2.0. Common Public Radio Interface: eCPRI Interface Specification (CPRI, 2019).

  6. Chen, S. et al. Vision, requirements, and technology trend of 6G: how to tackle the challenges of system coverage, capacity, user data-rate and movement speed. IEEE Wireless Commun. 27, 218–228 (2020).

    Article  Google Scholar 

  7. Che, D. Digital SNR adaptation of analog radio-over-fiber links carrying up to 1048576-QAM signals. In 2020 European Conference on Optical Communications (ECOC) Th3B.1 (IEEE, 2020).

  8. Ishimura, S., Bekkali, A., Tanaka, K., Nishimura, K. & Suzuki, M. 1.032-Tb/s CPRI-equivalent rate IF-over-fiber transmission using a parallel IM/PM transmitter for high-capacity mobile fronthaul links. J. Lightwave Technol. 36, 1478–1484 (2018).

    Article  ADS  Google Scholar 

  9. Le, S. T., Schuh, K., Chagnon, M., Buchali, F. & Buelow, H. 1.53-Tbps CPRI-equivalent data rate transmission with Kramers–Kronig receiver for mobile fronthaul links. In 2018 European Conference on Optical Communication (ECOC) We4B.4 (IEEE, 2018).

  10. Argyris, N. et al. A 5G mmWave fiber-wireless IFoF analog mobile fronthaul link with up to 24-Gb/s multiband wireless capacity. J. Lightwave Technol. 37, 2883–2891 (2019).

    Article  ADS  Google Scholar 

  11. Tanaka, K. et al. 1.314-Tbit/s (576 × 380.16 − MHz 5G NR OFDM Signals) SDM/WDM/SCM-based IF-over-fiber transmission for analog mobile fronthaul. In 2022 Optical Fiber Communications Conference and Exhibition (OFC) W4C.2 (IEEE, 2022).

  12. New radio (NR) physical layer enhancements (release 17, 3GPP TR 21.917 V1.0.0). 3GPP https://www.3gpp.org/ftp/Specs/latest/Rel-17/21_series (2022).

  13. Che, D., Yuan, F. & Shieh, W. High-fidelity angle-modulated analog optical link. Opt. Express 24, 16320–16328 (2016).

    Article  ADS  Google Scholar 

  14. Ishimura, S., Kao, H.-Y., Tanaka, K., Nishimura, K. & Suzuki, M. SSBI-free direct-detection system employing phase modulation for analog optical links. J. Lightwave Technol. 38, 2719–2725 (2020).

    Article  ADS  Google Scholar 

  15. Wang, J. et al. Delta-sigma digitization and optical coherent transmission of DOCSIS 3.1 signals in hybrid fiber coax networks. J. Lightwave Technol. 36, 568–579 (2018).

    Article  ADS  Google Scholar 

  16. Liu, X. Hybrid digital-analog radio-over-fiber (DA-RoF) modulation and demodulation achieving a SNR gain over analog RoF of >10 dB at halved spectral efficiency. In Optical Fiber Communication Conference (OFC) 2021 Tu5D.4 (IEEE, 2021).

  17. Zhu, Y. et al. Cascaded digital–analog radio-over-fiber for efficient SNR scaling at >10 dB per extra bandwidth. Opt. Letters 47, 3836–3839 (2022).

    Article  ADS  Google Scholar 

  18. Xu, Y. et al. Coherent digital-analog radio-over-fiber (DA-RoF) system with a CPRI-equivalent data rate beyond 1 Tb/s for fronthaul. Opt. Express 30, 29409–29420 (2022).

    Article  ADS  MathSciNet  Google Scholar 

  19. Hänsch, T. W. Nobel lecture: passion for precision. Rev. Modern Phys. 78, 1297 (2006).

    Article  ADS  Google Scholar 

  20. Hall, J. L. Nobel lecture: defining and measuring optical frequencies. Rev. Modern Phys. 78, 1279 (2006).

    Article  ADS  Google Scholar 

  21. Boulder Atomic Clock Optical Network (BACON) Collaboration. Frequency ratio measurements at 18-digit accuracy using an optical clock network. Nature 591, 564–569 (2021).

    Article  ADS  Google Scholar 

  22. Lisdat, C. et al. A clock network for geodesy and fundamental science. Nat. Commun. 7, 12443 (2016).

    Article  ADS  Google Scholar 

  23. Hu, H. et al. Single-source chip-based frequency comb enabling extreme parallel data transmission. Nat. Photon. 12, 469–473 (2018).

    Article  ADS  Google Scholar 

  24. Marin-Palomo, P. et al. Microresonator-based solitons for massively parallel coherent optical communications. Nature 546, 274–279 (2017).

    Article  ADS  Google Scholar 

  25. Corcoran, B. et al. Ultra-dense optical data transmission over standard fibre with a single chip source. Nat. Commun. 11, 2568 (2020).

    Article  ADS  Google Scholar 

  26. Lundberg, L. et al. Frequency comb-based WDM transmission systems enabling joint signal processing. Appl. Sci. 8, 718 (2018).

    Article  Google Scholar 

  27. Lundberg, L. et al. Phase-coherent lightwave communications with frequency combs. Nat. Commun. 11, 201 (2020).

    Article  ADS  Google Scholar 

  28. Mazur, M. et al. 12 b/s/Hz spectral efficiency over the C-band based on comb-based superchannels. J. Lightwave Technol. 37, 411–417 (2019).

    Article  ADS  Google Scholar 

  29. Geng, Y. et al. Coherent optical communications using coherence-cloned Kerr soliton microcombs. Nat. Commun. 13, 1070 (2022).

    Article  ADS  Google Scholar 

  30. Mazur, M. et al. 10 Tb/s PM-64QAM self-homodyne comb-based superchannel transmission with 4% shared pilot tone overhead. J. Lightwave Technol. 36, 3176–3184 (2018).

    Article  ADS  Google Scholar 

  31. Erkılınç, M. et al. Bidirectional wavelength-division multiplexing transmission over installed fibre using a simplified optical coherent access transceiver. Nat. Commun. 8, 1043 (2017).

    Article  ADS  Google Scholar 

  32. Parriaux, A., Hammani, K. & Millot, G. Electro-optic frequency combs. Adv. Opt. Photon. 12, 223–287 (2020).

    Article  Google Scholar 

  33. Wang, L. et al. Bi-directional self-homodyne transmission with MIMO-free DSP for next-generation data center interconnects. J. Lightwave Technol. 40, 6179–6189 (2022).

    Article  ADS  Google Scholar 

  34. Zhang, L. et al. Toward terabit digital radio over fiber systems: architecture and key technologies. IEEE Commun. Mag. 57, 131–137 (2019).

    Article  Google Scholar 

  35. Yoshida, M. et al. 10 channel WDM 80 Gbit/s/ch, 256 QAM bi-directional coherent transmission for a high capacity next-generation mobile fronthaul. J. Lightwave Technol. 39, 1289–1295 (2021).

    Article  ADS  Google Scholar 

  36. Zhu, Y. et al. 1λ 10.5 Tb/s CPRI-equivalent rate 1024-QAM transmission via self-homodyne digital-analog radio-over-fiber architecture. In European Conference and Exhibition on Optical Communication (ECOC) 2022 Th3A.5 (IEEE, 2022).

  37. Carlson, D. R. et al. Ultrafast electro-optic light with subcycle control. Science 361, 1358–1363 (2018).

    Article  ADS  Google Scholar 

  38. Zhang, C. et al. Air-gap Fabry–Pérot cavity filtered 30 nm broadband electro-optic frequency combs for high-order coherent communications. Opt. Lett. 47, 3724–3727 (2022).

    Article  ADS  Google Scholar 

  39. Zhang, M. et al. Broadband electro-optic frequency comb generation in a lithium niobate microring resonator. Nature 568, 373–377 (2019).

    Article  ADS  Google Scholar 

  40. Zhang, C. et al. Large-scale true-time-delay remote beamforming with EO frequency combs and multicore fiber. Opt. Lett. 46, 3793–3796 (2021).

    Article  ADS  Google Scholar 

  41. Ji, H., Sun, C. & Shieh, W. Spectral efficiency comparison between analog and digital RoF for mobile fronthaul transmission link. J. Lightwave Technol. 38, 5617–5623 (2020).

    Article  ADS  Google Scholar 

  42. Che, D. Analog vs digital radio-over-fiber: a spectral efficiency debate from the SNR perspective. J. Lightwave Technol. 39, 5325–5335 (2021).

    Article  ADS  Google Scholar 

  43. Nejad, R. M. et al. RoF data transmission using four linearly polarized vector modes of a polarization maintaining elliptical ring core fiber. J. Lightwave Technol. 36, 3794–3801 (2018).

    Article  ADS  Google Scholar 

  44. Yu, M. et al. Integrated femtosecond pulse generator on thin-film lithium niobate. Nature 612, 252–258 (2022).

    Article  ADS  Google Scholar 

  45. Stern, B., Ji, X., Okawachi, Y., Gaeta, A. L. & Lipson, M. Battery-operated integrated frequency comb generator. Nature 562, 401–405 (2018).

    Article  ADS  Google Scholar 

  46. Liu, Y. et al. A photonic integrated circuit–based erbium-doped amplifier. Science 376, 1309–1313 (2022).

    Article  ADS  Google Scholar 

Download references

Acknowledgements

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).

Author information

Author notes

  1. These authors contributed equally: Chenbo Zhang, Yixiao Zhu.

Authors and Affiliations

  1. State Key Laboratory of Advanced Optical Communication Systems and Networks, School of Electronics, Peking University, Beijing, China

    Chenbo Zhang, Bibo He, Jingjing Lin, Rongwei Liu, Weiwei Hu, Zhangyuan Chen & Xiaopeng Xie

  2. State Key Laboratory of Advanced Optical Communication Systems and Networks, Department of Electronic Engineering, Shanghai Jiao Tong University, Shanghai, China

    Yixiao Zhu, Yicheng Xu, Lilin Yi, Qunbi Zhuge & Weisheng Hu

  3. Peng Cheng Laboratory, Shenzhen, China

    Weisheng Hu & Zhangyuan Chen

Authors
  1. Chenbo Zhang
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Yixiao Zhu
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Bibo He
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Jingjing Lin
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. Rongwei Liu
    View author publications

    You can also search for this author in PubMed Google Scholar

  6. Yicheng Xu
    View author publications

    You can also search for this author in PubMed Google Scholar

  7. Lilin Yi
    View author publications

    You can also search for this author in PubMed Google Scholar

  8. Qunbi Zhuge
    View author publications

    You can also search for this author in PubMed Google Scholar

  9. Weiwei Hu
    View author publications

    You can also search for this author in PubMed Google Scholar

  10. Weisheng Hu
    View author publications

    You can also search for this author in PubMed Google Scholar

  11. Zhangyuan Chen
    View author publications

    You can also search for this author in PubMed Google Scholar

  12. Xiaopeng Xie
    View author publications

    You can also search for this author in PubMed Google Scholar

Contributions

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.

Ethics declarations

Competing interests

The authors declare no competing interests.

Peer review

Peer review information

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.

Additional information

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary Information

Supplementary Notes 1–8.

Rights and permissions

Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

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). https://doi.org/10.1038/s41566-023-01273-2

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/s41566-023-01273-2

Search

Advanced search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing