Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

IET conference proceedings.

Coexistence of quantum/classical signals over converged fiber/FSO links for intra-campus networking

Aristeidis Stathis, Argiris Ntanos, Nikolaos K. Lyras, Giannis Giannoulis, H. Avramopoulos

Published Nov 13, 2023• 2 citations
Publisher

Abstract

A converged fiber/FSO QKD coexistence scheme over an installed intra-campus link is demonstrated. Both FSO/fiber and fiber/FSO transmission configurations exhibited robust performance and stability, with QBER values below 3.9% while the quantum pulses co-propagated with an SFP signal intensity of 0 dBm.
DOI
10.1049/icp.2023.2414

Related papers

WDM-Enabled Classical/Quantum Coexistence During Full Daylight for Converged Fiber/FSO Networks

Aristeidis Stathis, Argiris Ntanos, Panagiotis Toumasis +3 more

We propose a WDM-enabled optical architecture in support of optimized classical/QKD coexistence over the deployed fiber/FSO infrastructure for 6G communications. A detailed analysis of 4-channel C-band WDM Classical/Quantum coexistence over deployed fiber/FSO links was conducted, showcasing the feasibility of QKD links for intra-campus connections in both mediums revealing QBER values (<3.2%) under daylight conditions.

International Conference on Optical Network Design and Modeling (ONDM)•May 6, 2024•2 citations

Practical approach to last-mile converged free-space and fiber QKD for secure city-scale networks

Aristeidis Stathis, Argiris Ntanos, Panagiotis Kourelias +6 more

Current Free-Space Optical Quantum Key Distribution (FSO-QKD) systems are mainly focusing on the development of critical components needed towards the realization of satellite-based QKD, relying on bulky optical telescopes equipped with expensive optical systems. The cost and complexity of these systems hinder the establishment of a practical FSO-QKD infrastructure deployed as the wireless last-mile segment of Quantum Communication Infrastructure for applications in urban environments. In this work, we experimentally demonstrate successful transmission of polarization encoded qubits over 0.5 km free space metropolitan link with enhanced noise suppression for both nighttime and daylight operation. Βy deploying two low-cost, Single Mode Fiber-coupled, optical terminals along with a prototype quantum sender station operating in C-band, Quantum Bit Error Rate (QBER) values below 3.5% were achieved, with expected Secure Key Rates up to 1 kbps during nighttime. The FSO link was integrated with existing in-building fiber infrastructure, demonstrating stable operation and acceptable QBER values below 5.5%, even when coexisting with intense C-band light signals (> 10 mW) propagating alongside the photonic qubits. The field trial and its comprehensive verification paves the way for practical FSO-QKD in city-scale environments, enabling end users to share quantum keys over kilometer-scale wireless links between building rooftops in last-mile connectivity scenarios.

Scientific Reports•Jan 28, 2026•2 citations

Coexistence of Classical and Quantum Signals in Hybrid Fiber and Free-Space Optics Links for QKD Integration

Nelson Jesus Muga, Sara T. Mantey, Diogo Cruz +7 more

Quantum key distribution (QKD) exploits the unique properties of quantum physics. It has evolved tremendously in recent years, attracting considerable attention as a privileged solution capable of enabling future-proof secure communication systems. This contrasts with classical cryptographic systems, whose security is based on computational security. However, before quantum cryptographic systems, e.g. QKD, could be widely implemented, in a coexistence scenario with classical signals, and made widely available to applications and users, they face several crucial challenges related to their real-world implementation. This paper presents our recent investigations to evaluate the coexistence between classical and quantum signals in hybrid fiber (multi-core fiber) and free-space optical links for an optimized integration of QKD systems in the installed fiber communication networks. We present results in terms of spontaneous Raman scattering, inter-core cross-talk and turbulence-induced optical power fluctuations.

International Conference on Transparent Optical Networks•Jul 14, 2024•2 citations

Deployment-Oriented Classical/Quantum coexistence in X-haul fiber link for B5G Networks

Argiris Ntanos, Dimitris Zavitsanos, Aristeidis Stathis +2 more

Coexistence of weak coherent pulses and intense light is experimentally demonstrated in a practical 5G X-haul scenario. Acceptable QBER measurements were obtained over 5 km fiber transmission by optimizing the parameters of single-photon sender/receiver stations.

•Jan 1, 2023•2 citations

Modeling and Experimental Assessment of QKD Systems in Coexistence with QKD-Encrypted High-Capacity DWDM Transmission

Eliana Mazza, Alessandro Gagliano, Alberto Gatto +9 more

We experimentally validated a design tool for optimizing integrated quantum-classical communication links with Raman flux measurements. We assessed commercial QKD system performance co-propagating with multiple coherent classical channels over 40- and 70-km fibers.

European Conference on Optical Communication•Sep 28, 2025•1 citation

Coexistence of classical and polarization-encoded QKD signals over deployed fiber

N. Linale, Adrià Sansa Perna, Ignacio H. López Grande +2 more

We report the first long-term field test of a polarization-encoding QKD system in C-band coexistence with classical signals over the same standard optical fiber. The system combines a self-stable polarization transmitter with a polarization control unit that stabilizes the link based on quantum metrics. This enables robust QKD operation over a metropolitan fiber link for several days, without requiring knowledge or control of the classical channels. The system can produce positive secret key rates of 422 kbps while coexisting with 0.7 mW classical power along a 50-km deployed link, achieving more than 98% uptime in the quantum channel.

Optics Express•Feb 13, 2026•0 citations
Current Free-Space Optical Quantum Key Distribution (FSO-QKD) systems are mainly focusing on the development of critical components needed towards the realization of satellite-based QKD, relying on bulky optical telescopes equipped with expensive optical systems. The cost and complexity of these systems hinder the establishment of a practical FSO-QKD infrastructure deployed as the wireless last-mile segment of Quantum Communication Infrastructure for applications in urban environments. In this work, we experimentally demonstrate successful transmission of polarization encoded qubits over 0.5 km free space metropolitan link with enhanced noise suppression for both nighttime and daylight operation. Βy deploying two low-cost, Single Mode Fiber-coupled, optical terminals along with a prototype quantum sender station operating in C-band, Quantum Bit Error Rate (QBER) values below 3.5% were achieved, with expected Secure Key Rates up to 1 kbps during nighttime. The FSO link was integrated with existing in-building fiber infrastructure, demonstrating stable operation and acceptable QBER values below 5.5%, even when coexisting with intense C-band light signals (> 10 mW) propagating alongside the photonic qubits. The field trial and its comprehensive verification paves the way for practical FSO-QKD in city-scale environments, enabling end users to share quantum keys over kilometer-scale wireless links between building rooftops in last-mile connectivity scenarios.
Quantum key distribution (QKD) exploits the unique properties of quantum physics. It has evolved tremendously in recent years, attracting considerable attention as a privileged solution capable of enabling future-proof secure communication systems. This contrasts with classical cryptographic systems, whose security is based on computational security. However, before quantum cryptographic systems, e.g. QKD, could be widely implemented, in a coexistence scenario with classical signals, and made widely available to applications and users, they face several crucial challenges related to their real-world implementation. This paper presents our recent investigations to evaluate the coexistence between classical and quantum signals in hybrid fiber (multi-core fiber) and free-space optical links for an optimized integration of QKD systems in the installed fiber communication networks. We present results in terms of spontaneous Raman scattering, inter-core cross-talk and turbulence-induced optical power fluctuations.
We report the first long-term field test of a polarization-encoding QKD system in C-band coexistence with classical signals over the same standard optical fiber. The system combines a self-stable polarization transmitter with a polarization control unit that stabilizes the link based on quantum metrics. This enables robust QKD operation over a metropolitan fiber link for several days, without requiring knowledge or control of the classical channels. The system can produce positive secret key rates of 422 kbps while coexisting with 0.7 mW classical power along a 50-km deployed link, achieving more than 98% uptime in the quantum channel.