Insights Blog

  • Jon Wilton

Hollow-Core Fibre: The route to a faster future?



The demand for lightning-fast broadband


As we continue to recover from the COVID-19 pandemic, demand is higher than ever for services that require lots of data. For most of us, this is most noticeable in the home: remote working, gaming, online video streaming.

While 95% of UK premises have access to superfast broadband (30 Mb/s), the race is now on to provide nationwide access to ‘gigabit’ broadband (1 Gb/s) by 2030, as per the government’s commitment in this year’s Levelling Up white paper. Old copper networks are unable to deliver such high speeds and are therefore being systematically phased out by single-mode optical fibre (SMF), which is being deployed at pace in FTTP access networks around the globe.


This copper-to-fibre upgrade represents a pivotal moment in the history of telecommunications in the UK and beyond, as we move away from infrastructure that has been in place for over a century. Many industries and services are ever-reliant on higher speed connectivity.


Is SMF the best solution, or are we overlooking a better alternative?


The emergence of hollow-core fibre


Conventional SMF in global use today passes light through a single fibre strand made from glass. Albeit incredibly pure and refined, there is no getting away from the fact that light travelling through glass will always travel slower through this medium than through a vacuum—as well as being affected by attenuation. This is where hollow-core fibre (HCF) technology offers greater promise, chasing a seemingly impossible solution to limitations governed by the fundamental laws of physics: by enabling the light to be transmitted via air or a vacuum.


HCF technology has improved since its emergence in the late 1990s, yet the central concept remains the same: an optical fibre guiding light through a hollow core (air or vacuum) with a lower refractive index than any single-mode core. Running the signal through an air-filled rather than glass-centre channel means the signal speed can be maintained at 99.9% of the speed of light (300 km/s), rather than at 66%. While there are now nuances in design and construction, the best performing HCF to date is the double-nested antiresonant nodeless fiber (DNANF) recently developed by Lumenisity, an offshoot from the University of Southampton’s Optoelectronics Research Centre (ORC).


Aside from transmission speed, another critical performance indicator of an optical fibre is its attenuation value, a measure of the light signal lost between input and output. First reported in March of this year, Lumenisity’s DNANF achieved attenuations of 0.22 dB/km at 1310nm (O-band) and of 0.174 dB/km at 1550nm (C-band), matching that of commercial SMF at some frequencies (C-band) and surpassing it in others (O-band). This recent ground-breaking development has further pushed HCF into the spotlight, with various industries now considering possible applications of the technology in their fields.





Examining potential applications of hollow-core fibre


The excitement around HCF has led to a number of key trials which may shed light on the best use cases for Lumenisity’s CoreSmart® solution. One such trial was carried out in March by euNetworks. Using Lumenisity’s latest solution, the company installed a 7km route of HCF between the LON1 and London Stock Exchange data centres. Through 50% faster data transmission, latency was cut by 1/3 compared to SMF. This finding has huge implications for financial trading and is also of interest for gaming networks. Longer trial routes are now being planned, while there is confidence that the decreased latency can be maintained even with increased separation of data centres, an exciting prospect for both high frequency traders and hyperscalers.


Telecoms giant BT, in early testing with Mavenir, also noted that HCF’s faster transmission and reduced latency could help to lower mobile network costs, allowing greater distances between antennas and back-end cabinets and therefore larger areas to be served by fewer cabinets. In a different trial, instead with a focus on potential applications in quantum security, BT deployed a quantum key distribution (QKD) system using 6km of Lumenisity’s HCF solution. Reporting a reduction in latency and signal interference, the trial exposed the potential for HCF to be deployed in quantum communications, boosting security for data transmission through the safer delivery of quantum keys for quantum encryption.


Another potential application of the technology is in laser machining. Experiments by Lumenisity’s Francesco Poletti and the ORC showed that 1kw of continuous laser power at 1070nm could be beamed through a 1km-long stretch of HCF, compared to SMF’s capacity of tens of metres at this wattage, avoiding the nonlinear effects seen with conventional SMF given the nested design that gives (D)NANF its name. This ability to deliver high-power beams over such distances could be a huge discovery for the field of laser machining.


Could hollow-core fibre change the face of FTTP?


HCF has been shown to match or better performance of conventional SMF at different wavelengths, showcasing improvements with attenuation, latency, nonlinearity and dispersion. The excitement around this new fibre technology in various industries is clear, but just how realistic is its application in FTTP access networks?


With a predicted increase of 10+ million live connections in the UK by 2025, the demand for fast and dependable fibre is ever-greater. Unfortunately, HCF technology cannot yet answer this demand, for a multitude of reasons. Not only is the geography of the UK very awkward, but to use HCF in FTTP access networks to increase broadband speeds would require rebuilding existing FTTP deployments. Still an emerging technology, HCF is not yet being manufactured in volume and so comes at an extreme price premium, which is not expected to change for several years. Currently HCF’s use in FTTP access networks in the UK and across the globe seems a very distant possibility. The ongoing evolution of PON and other technologies will also continue to increase the performance, speed and commercial lifespan of existing SMF, further pushing the goalposts for HCF.


So, although HCF’s use in the consumer access networks is some way off, we may see many core network and business applications starting to incorporate this technology.


What Cambridge MC can do to help


Having lived with and worked around the limitations of SMF for 40 years or so, HCF will provide a step-change in optical networking and the applications it can support.


These will have far-reaching impacts on digital transformation strategies that will be adopted by our enterprise clients. HCF is a truly fascinating new technology and, although still in its infancy, already demonstrates a capacity for lower latency networking in the years to come. It may be some time before we benefit from HCF in the home when gaming or streaming our favourite Netflix shows, but B2B applications of HCF are more likely, particularly with financial trading and data centres.


With a reputation for excellence and expertise in the telecommunications industry, Cambridge Management Consulting will continue to track this technology and many others as they emerge. We pride ourselves on being ahead of the curve, and our consultants are on many panels and boards that advise on and predict future technology trends. When commercial opportunities for HCF emerge, we will be able to advise your organisation on adoption strategies.