AI 中文总结
本研究针对量子网络中量子与经典信号共存的挑战，在真实城域光纤网络中分析O波段经典信号产生的拉曼散射，识别低噪声光谱区域，为量子信道分配提供指南，助力构建稳健可扩展的量子基础设施。
AI 中文摘要
光纤基础设施中量子信号与经典信号的共存是构建大规模量子网络的重大挑战，因为拉曼散射等噪声源会严重影响纠缠分发及基于纠缠的量子协议。本研究分析了经典O波段信号在用于纠缠分发的C波段产生的拉曼散射，主要贡献在于在真实城域光纤网络中研究这些效应，突破了受控实验室实验的局限，转向已部署的电信环境。实验采用商用光源和窄带激光器，在7公里城域光纤链路上进行测量，结果显示实验室条件下的测量与城域环路内已部署光纤中观测到的局部光谱异常吻合良好。因此，研究表明，当量子信号在C波段与同一光纤内的O波段经典信道共存时，需谨慎选择工作频率，因为拉曼散射及其他现实噪声源会严重影响量子传输的质量与稳定性。研究特别识别出受拉曼噪声影响较小的光谱区域，为优化量子信道分配提供实用指南；还证明在现实部署中，拉曼诱导噪声是量子信噪比（SNR）的主要贡献，超过背景噪声和探测器噪声。总体而言，研究结果为在现有光纤网络上部署量子通信系统提供了实用见解，支持构建稳健且可扩展的量子基础设施。
英文摘要
The coexistence of quantum and classical signals in optical fiber infrastructures represents a major challenge for large-scale quantum networks, as noise sources such as Raman scattering can significantly impact entanglement distribution, and the quantum protocols based on it. In this work, we analyze Raman scattering in the C-band, used for entanglement distribution, generated by a classical the O-band signal. The main contribution of this study lays in investigating these effects in a real metropolitan-fiber network, moving beyond controlled laboratory experiments to deployed telecommunication environments. Measurements are performed over a 7 km metropolitan fiber link using commercial sources and narrowband lasers. The experimental results shows good agreement between the measurements taken under laboratory conditions, although, within the metropolitan-scale loop, localized spectral anomalies are observed in the deployed fibers. Therefore, our results show that, whenever a quantum signal propagates in the C-band alongside an O-band classical channel within the same fiber, careful selection of the operating frequency is required, as Raman scattering and other real-world noise sources can significantly affect the quality and stability of the quantum transmission. In particular, we identify spectral regions that are less affected by Raman noise, thereby providing practical guidelines for optimal quantum channel allocation. We demonstrate that Raman-induced noise constitutes a dominant contribution to the quantum signal-to-noise ratio (SNR) in realistic deployments, beyond background and detector noise. Overall, our findings offer practical insights for deploying quantum communication systems over existing fiber networks, supporting the development of robust and scalable quantum infrastructures.
CommentsInvited Paper in IEEE SMARTCOMP. This work has been funded by the European Union under Horizon Europe ERC-CoG grant QNattyNet ("Quantum-Native Communication Networks: from Quantum Message to Quantum Functioning"), n.101169850. Details at https://qnattynet.quantuminternet.it
