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arXiv:2512.02701 · Workshop on Specialty Optical Fibers and Their Applications (WSOF)

Multi-node quantum key distribution network using existing underground optical fibre infrastructure

Mariella Minder, Andreas Siakolas, Stephanos Yerolatsitis, Konstantinos Katzis, Kyriacos Kalli

quant-phSubmitted Dec 2, 2025• Announced Dec 3, 2025• 0 citations
arXivHTMLPDF

Abstract

Quantum key distribution (QKD) offers unconditional information security by allowing two distant users to establish a common encryption key resilient to hacking. Resultingly, QKD networks interconnecting critical infrastructure and enabling the secure exchange of classified information, can provide a solution to the increasing number of successful cyberattacks. To efficiently deploy quantum networks, the technology must be integrated over existing communication infrastructure, such as optical fibre links. Yet, QKD poses stringent requirements on the conditions of the network over which it is deployed. This work demonstrates the first quantum communication network in Cyprus via the deployment of a multi-node quantum network, exploiting existing commercial underground optical fibre. The network employs bidirectional occupation of fibres and wavelength multiplexing in a ring architecture to achieve, with minimal use of dark fibres, high-rate QKD. Results obtained reveal consistent key generation rates across all nodes, confirming reliable operation in a real-world environment. This deployment highlights the feasibility of leveraging existing telecom infrastructure for quantum-secured communication, marking a significant step toward scalable and cost-effective quantum networks suited for critical applications.

Journal reference
Proc. SPIE 13522, Eighth International Workshop on Specialty Optical Fibers and Their Applications (WSOF 2025), 1352219 (29 May 2025)
DOI
10.1117/12.3066715
Comments
5 pages, 3 figures

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As quantum computing threatens to compromise classical cryptographic systems, the need for future-proof, information-theoretically secure methods of communication has become critical. Quantum Key Distribution (QKD) leverages the fundamental principles of quantum mechanics to enable the secure generation and exchange of encryption keys, immune to computational attacks. This paper investigates the integration of QKD into telecom infrastructures to enable ultra-secure communication. We examine the performance of key QKD protocols, such as BB84 and E91, over fiber-optic and free-space channels, and simulate their deployment within realistic metropolitan network topologies. Results show that secure key rates of up to 10 kbps can be maintained over 50–80 km fiber links with Quantum Bit Error Rates (QBER) below 5%. The study also explores architecture models based on trusted relay nodes and WDM coexistence, highlighting practical deployment considerations. Our findings suggest that QKD is a viable enhancement for telecom security and a necessary foundation for long-term quantum-resilient communication systems.