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International Conference on Transparent Optical Networks

Towards a smooth integration of quantum key distribution in metro networks

Slaviša Aleksić, Dominic Winkler, Florian Hipp, Andreas Poppe, Gerald Franzl, Bernhard Schrenk

Published Jul 1, 2014• 14 citations
Publisher

Abstract

Quantum key distribution (QKD) systems have already reached a reasonable level of maturity. However, a smooth integration of commercial QKD systems in metropolitan area networks has still remained challenging because of technical and economical obstacles. Mainly the need for dedicated fibers and the strong dependence of the secret key rate on both loss budget and background noise in the quantum channel hinder a practical, flexible and robust implementation of QKD in current and next-generation optical metro networks. In this paper, we discuss these obstacles and present approaches to share existing fiber infrastructures among quantum and classical channels. Particularly, a proposal for a smooth integration of QKD in optical metro networks, which implies removing spurious background photons caused by lasers, amplifiers and nonlinear effects in optical fibers, is presented and discussed.

DOI
10.1109/icton.2014.6876369

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Quantum key distribution (QKD) systems have already reached a reasonable level of maturity. However, a smooth integration and a wide adoption of commercial QKD systems in metropolitan area networks has still remained challenging because of technical and economical obstacles. Mainly the need for dedicated fibers and the strong dependence of the secret key rate on both loss budget and background noise in the quantum channel hinder a practical, flexible and robust implementation of QKD in current and next-generation optical metro networks. In this paper, we discuss these obstacles and present approaches to share existing fiber infrastructures among quantum and classical channels. Particularly, a proposal for a smooth integration of QKD in optical metro networks, which implies removing spurious background photons caused by optical transmitters, amplifiers and nonlinear effects in fibers, is presented and discussed. We determine and characterize impairments on quantum channels caused by many classical telecom channels at practically used power levels coexisting within the same fiber. Extensive experimental results are presented and indicate that a practical integration of QKD in conventional optical metro networks is possible.
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It is well known that optical access networks are able to provide high data rates over long distances and to a reasonable number of users. Security and privacy are always a challenge for public accessible network infrastructures. Especially in time-division multiplexing passive optical networks (TDM-PONs), in which the downstream signal is broadcasted to all users connected via the same wavelength channel in a shared fiber link, privacy can be a critical concern. Although encryption at the application layer can provide a high level of security, this can be achieved only if the encryption key distribution is perfectly save. On the other hand, encryption on the physical layer such as quantum cryptography or, more precisely, quantum key distribution (QKD) is a very promising approach to achieve secure communication. However, there remain several issues that have to be solved before the quantum cryptography reaches the maturity level needed for a cost effective implementation in practical networks. In this paper, we address quantum key distribution (QKD) over passive optical access networks, which is an enabling technology required to cost efficiently deploy practical quantum encrypted data communication in the access area. We study different methods to integrate QKD systems in conventional optical access networks and quantitatively evaluate their suitability for a potential implementation.
Quantum computing poses a threat to the standard cryptographic primitives and requires the implementation of quantum-safe designs in the existing network infrastructures. Quantum Key Distribution (QKD) has been used to provide information-theoretic security but its compatibility with high capacity wavelength-division multiplexing (WDM) systems is a challenge to its deployment in metropolitan networks. In this paper, the architectural design and outcomes of a field trial assessing the concept of co-propagation of quantum and classical signals in a dense WDM metro environment are introduced. We discuss and measure the performance of multi-span fibres and measure quantum bit error rates in the presence of highlypower classical loading and the stability of the end-to-end key generation. A hybrid architecture that incorporates both QKD and classical post-quantum solutions is introduced to make them more resilient, optimized in terms of spectrum usage, and scalable to operator-grade services. The experimental findings show that QKD can be smoothly incorporated into the metro networks without affecting throughput and latency, indicating a way forward to practical quantum safe communications to future critical infrastructures.
The integration of quantum key distribution (QKD) into passive optical networks (PONs) poses new challenges due to the specific characteristics of the access network, as the high losses from passive splitters and the spontaneous Raman scattering noise generated by classical channels co-propagating in the same optical fiber. In this paper, different QKD technologies and implementations are compared, taking into account both discrete-variable and continuous-variable QKD systems to maximize the achievable secret key rate performance in single-fiber bidirectional PONs.