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Multiplexing QKD systems in Conventional Optical Networks

Alex Ciurana Aguilar, Vicente Martín Ayuso, Jesús Martínez-Mateo, Andreas Poppe, Mercedes Soto, Nino Walenta, Hugo Zbinden

Published Sep 10, 2012• 2 citations
OpenAlex

Abstract

Current QKD designs try to keep the quantum channel as error free as possible by using a separate physical medium for this purpose. In the most common case, this means the exclusive use of an optical fiber for the quantum channel, precluding its use for any other purpose. In current optical networks, the fiber is the single most expensive element and this poses a major problem from a cost and availability point of view. Sharing the fiber is thus mandatory for the widespread adoption of QKD. The objective of this communication is to propose a general scheme and present some preliminary measurements of a metropolitan area network (MAN) designed to multiplex of the order of 64 addressable quantum channels and the associated QKD classical service signals on a single dark fibre. It uses as much existing components and infraestructure as possible in an attempt to simultaneously lower most of the practical barriers for the adoption of QKD.

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Current QKD designs try to keep the quantum channel as error free as possible by using a separate physical medium for this purpose. In the most common case, this means the exclusive use of an optical fiber for the quantum channel, precluding its use for any other purpose. In current optical networks, the fiber is the single most expensive element and this poses a major problem from a cost and availability point of view. Sharing the fiber is thus mandatory for the widespread adoption of QKD. The objective of this communication is to propose a general scheme and present some preliminary measurements of a metropolitan area network (MAN) designed to multiplex of the order of 64 addressable quantum channels and the associated QKD classical service signals on a single dark fibre. It uses as much existing components and infraestructure as possible in an attempt to simultaneously lower most of the practical barriers for the adoption of QKD.
Quantum Key Distribution (QKD) is maturing quickly. However, the current approaches to its network use require conditions that make it an expensive technology. All the QKD networks deployed to date are designed as a collection of dedicated point-to-point links that use the trusted repeater paradigm. Instead, we propose a novel network model in which QKD systems use simultaneously quantum and conventional signals that are wavelength multiplexed over a common communication infrastructure. Signals are transmitted end-to-end within a metropolitan area using optical components. The model resembles a commercial telecom network and takes advantage of existing components, thus allowing for a cost-effective and reliable deployment.
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.
Quantum Key Distribution (QKD) is maturing quickly. However, the current approaches to its application in optical networks make it an expensive technology. QKD networks deployed to date are designed as a collection of point-to-point, dedicated QKD links where non-neighboring nodes communicate using the trusted repeater paradigm. We propose a novel optical network model in which QKD systems share the communication infrastructure by wavelength multiplexing their quantum and classical signals. The routing is done using optical components within a metropolitan area which allows for a dynamically any-to-any communication scheme. Moreover, it resembles a commercial telecom network, takes advantage ofexisting infrastructure and utilizes commercial components, allowing for an easy, cost-effective and reliable deployment.
Quantum Key Distribution (QKD) is maturing quickly. However, the current approaches to its application in optical networks make it an expensive technology. QKD networks deployed to date are designed as a collection of point-to-point, dedicated QKD links where non-neighboring nodes communicate using the trusted repeater paradigm. We propose a novel optical network model in which QKD systems share the communication infrastructure by wavelength multiplexing their quantum and classical signals. The routing is done using optical components within a metropolitan area which allows for a dynamically any-to-any communication scheme. Moreover, it resembles a commercial telecom network, takes advantage of existing infrastructure and utilizes commercial components, allowing for an easy, cost-effective and reliable deployment.
Quantum key distribution (QKD) allows authenticated communicating entities to generate and distribute random keys with security guaranteed by the principles of quantum mechanics. Usually, the deployment of optical fibre-based QKD links requires a dark fibre for the quantum channel of the QKD link. However, the availability of dark fibre is scarce for field deployments and involves higher capital expenses. In this paper, we propose a QKD solution where the quantum channel and classical channel of the QKD link are multiplexed on the same fibre carrying a data traffic of 100 Gbps using wavelength division multiplexing (WDM). The solution will facilitate rapid upgradation of existing communication networks with quantum security, especially in metropolitan networks.
A major road-block in bringing QKD to the market is the missing scalability of a single QKD-link connecting two users to a use-case with many users in the same metropolitan area network (MAN). The typical trusted node concept used for this, beyond requiring the trust on all intermediate nodes, is not able to distribute entanglement without the help of quantum manipulations that have yet to be demonstrated. Here we extend the concept of entanglement to many pairs of users by the introduction of novel structures. The goal of this work is the design of a MAN for quantum and co-propagating classical signals to allow an arbitrarily high number of users not bounded by e.g. the number of CWDM or DWDM channels in the ITU grid. The number of coexistent multiplexed links is clearly limited by this usable fibre bandwidth, but the network must be able to select the corresponding user out of a large pool of possible communication partners (as in mobile phone networks).