BT probes fiber’s future with hollow core trial

U.K. operator BT revealed it is trialing an advanced fiber technology that has the potential to slash latency by up to 50% compared to traditional fiber, a benefit it said could help lower mobile network costs and enable advanced used cases.

Andrew Lord, BT’s head of optical network research, told Fierce trials underway at BT Labs in Ipswich alongside open RAN vendor Mavenir and fiber supplier Lumenisity aim to deliver a “full characterization” of what is known as hollow core fiber (HCF). Among other things, he said tests are focused on determining the technology’s latency performance, thermal stability, ease of handling and cabling, and performance at a wide range of wavelengths. He noted initial findings will be published at an industry conference next week, with additional results set to be revealed in the coming months.

While traditional fiber relies on solid glass strands to conduct light signals sent by lasers, hollow core fiber uses an air-filled center channel within an outer glass shell to route the same. By using an air channel, the technology reduces signal loss seen in traditional fiber and enables the cable to maintain the “signal speed at very close to the ultimate speed of light,” BT explained in a press release.

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BT noted HCF could be used for a range of use cases, including high frequency trading or ultra-secure communications but emphasized its potential benefits for mobile network deployments. It noted early testing conducted with Mavenir showed hollow core fiber could increase the distance between antennas and back-end processing cabinets, potentially allowing more sites to be served by fewer cabinets and thereby reducing mobile network costs.

A Lumenisity representative told Fierce that aside from mobile backhaul “there is a lot of interest in geographic expansion of the data center interconnect leveraging the high bandwidth capability of hollow core coupled with the extension in reach for a given latency envelope.” The representative added interest in the technology is “global” and includes players involved in high-frequency trading, gaming networks, hyperscale data centers and fixed and wireless networks.

Lumenisity was formed in 2017 and developed a hollow core fiber that can be spliced into conventional fiber networks. In April 2021, infrastructure company euNetworks Fiber UK Limited rolled out the hollow core solution to serve the London Stock Exchange, marking what Lumenisity touted as “the first commercially available deployment of this technology in the world.”

Lord said he doesn’t expect hollow core fiber to replace any existing fiber but “more likely install alongside it. I would expect the HCF to come with a price premium for several years to come, so would be used in niche situations to start with.” Over time, “volume fiber manufacture should reduce the cost of the fiber and this will open up more opportunities,” he added.