- AWS told Fierce it is deploying hollow core fiber to connect 10 data centers
- Supply remains an issue, though ecosystem partners like Relativity Networks and Viavi are stepping up as hyperscale interest grows
- Eventually, HCF could replace traditional fiber as the default for long haul routes, AWS' Matt Rehder said
After about a year of tinkering, AWS has decided hollow core fiber (HCF) is ready for prime time. Matt Rehder, AWS’ VP for Core Networks, told Fierce the hyperscaler is deploying HCF to connect about 10 data centers today. But while Rehder said he sees a much larger role for HCF in the future, there’s just one problem: supply.
“The real challenges are the manufacturability of it, which combines with cost,” Rehder told Fierce. “It’s been so hard to manufacture, especially strands of any length where you could actually use it to connect multiple data centers together over long distances. The yields are very poor, [and] the cost of manufacturing is very high.”
While regular fiber is typically made of one solid strand of glass, hollow core fiber calls for several hollow glass tubes to be situated inside a larger tube. Producing this kind of fiber is a bit tricky to begin with, nevermind manufacturing it at scale.
While there have been several breakthroughs in manufacturing recently that have allowed both AWS and Microsoft to deploy HCF in production, demand for HCF remains significantly higher than the available supply.
Supply hurdles
Though only AWS and Microsoft have been public about their HCF plans, both Google and Meta also appear to be eyeing the technology. The thing is, there aren’t that many HCF suppliers in the market today.
Lumenisity – one of the OG HCF players – was scooped up by Microsoft in 2022, leaving the market with something of a vacuum. Today’s competitors include Lightera (formerly OFS), and China-based YOFC and Hengtong Optic-Electric. U.S.-based startup Relativity Networks has also emerged to fill the void, partnering with fiber manufacturer Prysmian in March 2025 to spin up new HCF production lines.
Relativity Networks CEO Jason Eichenholz told Fierce that much of 2025 was spent working with Prysmian to perfect HCF production in its Netherlands plant. Over the next few years, he said it hopes to expand production volume from tens of thousands of kilometers to hundreds of thousands of kilometers by leveraging Prysmian’s global manufacturing footprint. The goal, he added, is to meet what he characterized as “insatiable demand” for HCF.
“I will sell every kilometer of fiber I can make,” Eichenholz said. The CEO added he expects two or three more entrants in the HCF space in the near term, but “what we’re hearing from hyperscalers is if you can’t deliver tens of thousands or hundreds of thousands of kilometers of fiber, you’re going to be a niche player.”
To put a finer point on it: Eichenholz said demand is so high that Relativity Networks actually received its first HCF purchase order in 2024 before the company even had any employees. “We have a hyperscaler that wants pretty much everything we can make,” he stated.
Eichenholz declined to name the hyperscale customer, but said it was one of the big five cloud players: Meta, Google, Amazon, Oracle and Microsoft. Pressed on this point – given Microsoft’s ownership of Lumenisity and its recent HCF supply agreements with Corning and Heraeus – Eichenholz conceded the customer is not Microsoft.
Rehder mentioned AWS has been working closely to co-design solutions with partners in the HCF ecosystem, “trying to help them along” and attempting to spur investment by letting players know that the tech giant “would be there to purchase” HCF if the manufacturability issue was solved.
He added AWS is currently working with three HCF suppliers. Asked if he was familiar with Relativity Networks, Rehder said no.
Testing, testing
As for what the process of getting HCF into production looked like, Rehder said AWS spent a little over a year testing HCF and exploring issues like whether HCF would work with existing DWDM optical technology and how hard it is to repair if cut.
AWS wanted to avoid specialized equipment for hollow core, to avoid creating yet another layer of supply and integration complexity. Thankfully, AWS found that HCF is indeed compatible with its existing optical technology, though the signals do need about 10% to 20% more amplifiers along the route than standard fiber. Rehder said, however, he expects that amplifier number to go down as the manufacturing quality of HCF improves.
HCF seems to have caught on enough that it has gained the attention of test and measurement company Viavi. The company this week announced what it called the “industry’s first medium and long-range bidirectional testing and certification solution.” Viavi said the solution has been proven out via testing conducted with three major hyperscalers as well as fiber manufacturers and specialist contractors.
A hollow future
For now, Rehder said AWS is purely using hollow core fiber in metro areas where it needs the ability to expand its search area for land and power. That’s because HCF can deliver the same latency as regular fiber over greater distances, thus expanding where it can locate data centers without compromising its latency thresholds.
But looking into the future, Rehder said he can see a world where new fiber paths begin to be built purely with HCF. It could even make its way into the data centers themselves for the short hops between servers.
“If you could, you would want all of your fiber paths to be hollow core just because it’s lower latency and that’s going to benefit some applications at some point,” he concluded. “You won’t do that until costs come down to a certain point, but I think that’s an inevitability.”