BT UK Trials Quantum Key Distribution via Hollow Core Fibre Cable

Telecoms giant BT and Lumenisity, a spin-out from Southampton University, has taken two of their recent developments in the UK and today combined them in order to conduct the “world’s first” trial of Quantum Key Distribution (QKD), a method of ultra-secure communications, over hollow core fibre optic cable.

Last year BT and Toshiba succeeded in establishing the UK’s first “industrial deployment” of a quantum-secure network using Openreach’s “standard” fibre optic infrastructure (here). Should such a communication be intercepted along the way, the sender will be able to tell that the link has been tampered with, and the stolen photons cannot then be used as part of the key, thus rendering the data stream incomprehensible to a hacker.

The key rate of the QKD system, mentioned above, ran at just 1.1Mbps (each encryption key has a length of 256 bits), while the encrypted data link itself was running at 10Gbps, although it could go up to several hundred gigabits per second and at distances of up to 600km (here).

Since then BT has also started trials of a new type of hollow core optical fibre cable – Nested Anti-Resonant Nodeless Fibre (NANF) – at their BT Labs R&D facility in Adastral Park (Ipswich), which could in theory be more resistant to damage, while also delivering better performance (e.g. latency) for future broadband ISP and mobile connectivity services.

Naturally, BT has now taken both developments and combined them in order to conduct their latest trial, which operated their QKD system using commercial equipment over a 6km long Lumenisity CoreSmart® cable with a hollow, air-filled centre, revealing potential benefits such as “reduced latency and no appreciable crosstalk [interference].”

Lumenisity’s cable also demonstrated further benefits for the deployment of QKD, as “commercial telecommunications equipment will not need to be optimised in order to send a data-encrypted key.” This is critically important because the equipment can be used normally without modifications, an issue that creates added complications for sending secure signals over standard fibre.

Professor Andrew Lord, BT’s Head of Optical Network Research, said:

“This is an exciting milestone for BT, accelerating the UK’s lead in quantum technologies that will play an important role in future communications systems globally. We’ve proven a range of benefits that can be realised by deploying hollow core fibre for quantum-secure communication. Hollow core fibre’s low latency and ability to send QKD over a single fibre with other signals is a critical advancement for the future of secure communications.”

All of this will come in handy for future deployments of hollow core fibre, which initially seems likely to have more relevance for new national and core network links than for connecting individual homes and businesses via the local access network. Indeed, we aren’t even close to maximising the capability of existing optical fibres in the local access network (e.g. those used for Fibre-to-the-Premises (FTTP) broadband), which will exist for many decades and possibly even longer.