- Hollow core fiber can carry more optical power because light travels mostly through air, STL Group CTO Badri Gomatam told Fierce
- The catch: Hollow core fiber is harder and slower to manufacture at scale than conventional solid-core fiber
- Gomatam sees near-term promise for multicore fiber inside the data center, while hollow core fiber has a stronger case for links between data centers
Hyperscalers have been pretty clear about why hollow core fiber has their attention: AI is forcing data centers to stretch farther apart without letting latency blow up the network design. But Badri Gomatam, group CTO at Sterlite Technologies Ltd., thinks the industry should be looking beyond the latency story.
Gomatam told Fierce Network one of hollow core fiber’s most important advantages is its ability to tolerate higher optical power without the same level of interference that shows up in traditional solid glass fiber.
“When you transmit in air, you don’t have this interaction between the light and the air as strongly as it is for light and glass,” Gomatam said. That reduction in resistance means “you can just pump in a lot more energy,” extending reach, he added.
Why power matters
Here’s why pumping up the power levels works in hollow core fiber better than if you tried the same thing with single-mode fiber.
In standard single-mode fiber, adding more wavelengths and more launch power eventually creates a bottleneck in the form of cross-talk. That is, channels begin to interfere with one another, producing bit errors even if enough light reaches the receiver. Hollow core fiber doesn’t eliminate physics, but Gomatam said the form factor dramatically reduces the limits on how hard operators can push a fiber strand.
That matters because the AI data center buildout is not just creating a need for faster links. It is increasing pressure on every part of the optical transport stack — bandwidth, reach, power, duct space and the ability to connect more buildings without constantly rebuilding the physical plant.
AWS has said hollow core fiber can provide roughly a 30% latency improvement over standard fiber and help it reach nearly 50% farther while staying within the same latency target. The cloud giant is already deploying the technology to connect about 10 data centers, though it told Fierce supply remains a limiting factor.
Microsoft has also moved to scale hollow core fiber, striking agreements with Corning and Heraeus Covantics to increase global HCF production for Azure. Corning said its North Carolina fiber and cable manufacturing facilities will produce Microsoft’s hollow core fiber as part of that collaboration.
The manufacturing problem
For now, though, hollow core fiber remains much harder to make than standard fiber. Gomatam described the basic structure as “nested tubes of glass within a tube of glass.” That creates a precision manufacturing challenge: as the preform is heated, drawn and cooled, the hollow structures inside have to hold their shape and dimensions.
“If it is hollow, these little nested structures have to be kind of held in place through the process of drawing,” he said. “What it means is you draw fiber per tower at a slower rate than you’re able to today with solid core fiber.”
Gomatam isn’t the only one who has pointed out this challenge. AWS’ Matt Rehder told Fierce the “real challenges are the manufacturability of it,” including poor yields and high manufacturing costs for fiber spans long enough to connect multiple data centers.
Hollow core vs. multi-core
STL is seeing interest in both hollow core and multi-core fiber, but Gomatam framed them as solving somewhat different problems on different timelines. Multi-core fiber, he said, is easier to imagine moving through customer qualification in the near term because it is closer to what operators already know how to splice and connect.
“It is faster to convince somebody about a multi-core deployment,” Gomatam said, pointing to space, weight and duct-capacity constraints. “Inside the data center, multi-core is a very good story.”
Gomatam added multi-core is also on somewhat firmer footing because underlying standards work exists, while hollow core standards are still developing.
Hollow core, by contrast, has a stronger case outside the data center, where reach and latency can change the economics of where operators and hyperscalers place buildings. But it also comes with a steeper operational learning curve, including splicing, training, termination and connector ecosystems that still need to mature.
Gomatam said informed customers are asking the right questions: when the technology will be ready, when the cost structure will improve and where the total cost of ownership makes sense. But he added standardization could prove especially important if hollow core is to move beyond hyperscaler-led deployments and into a broader telecom ecosystem.
Read more about hollow core and multi-core fiber on Fierce Network:
STL, Corning explain multi-core fiber and its importance for data centers
AWS wants more hollow core fiber than it can get
AWS is using hollow core fiber to go the distance
Microsoft preps cloud for AI with Corning, Heraeus hollow core fiber deal