Hollow-Core Fiber in 2026: How Microsoft, Lumenisity, Corning, and Sumitomo Are Sending Light Through Air to Cut Latency and Beat the Speed Limit of Glass
- Internet Pros Team
- July 2, 2026
- Networking & Security
Every message you send, every video you stream, and every AI model being trained right now rides on light pulsing through hair-thin strands of glass. For fifty years those strands have had one quiet limitation baked into physics: light travels slower through solid glass than it does through air. In 2026 a redesigned kind of optical fiber is finally erasing that penalty at scale. Called hollow-core fiber (HCF), it guides light down a channel of air instead of glass - so signals move faster, arrive with lower latency, and carry more data with less distortion. After decades stuck in the lab, hollow-core fiber is being pulled into real networks, and Microsoft is leading the charge inside its own data centers.
What Hollow-Core Fiber Actually Is
A conventional optical fiber has a solid glass core at its center, and light stays trapped inside it by bouncing off a surrounding glass cladding of slightly lower refractive index. It works beautifully, but the light is traveling through glass the whole way - and glass slows light down to about two-thirds of its top speed in a vacuum. Hollow-core fiber flips the design: the core is a hollow tube of air (or near-vacuum), and a ring of precisely shaped microscopic glass tubes around it keeps the light confined to that empty center.
Because the light spends almost all of its journey in air rather than glass, it travels roughly 47% faster - close to the speed of light in a vacuum. Over a long link that translates into meaningfully lower latency, the delay between sending a bit and receiving it. It also means the light barely interacts with glass at all, which cuts a whole family of distortions that limit conventional fiber.
How You Guide Light Through Nothing
The Old Way: Photonic Bandgap
Early hollow-core designs used a dense honeycomb lattice of glass and air around the core that acted like a mirror for a narrow band of wavelengths, reflecting light back into the empty center. It proved the idea worked but suffered from high loss and a limited usable spectrum.
The Breakthrough: NANF
The modern design, the nested anti-resonant nodeless fiber (NANF), surrounds the air core with a simple ring of thin, nested glass tubes. Their walls are tuned so light of the target wavelength cannot resonate in the glass and is pushed back into the air - guiding it with astonishingly low loss.
The NANF breakthrough matters because for years hollow-core fiber lost too much signal to be practical. Then researchers drove its attenuation below 0.1 dB/km - beating the loss of the standard single-mode fiber that has carried the internet for decades. Once a faster fiber also became a lower-loss fiber, the last big objection fell away.
"For fifty years we accepted that light in a fiber runs a third slower than light in a vacuum, because the alternative did not work well enough. Hollow-core changed the question. When you can send light through air and lose less signal than you would through glass, there is no longer a trade-off to argue about - just a manufacturing problem to solve."
Why It Matters: Latency, Bandwidth, and AI
Speed of light sounds abstract until you are moving money or training a model. In high-frequency trading, shaving a microsecond off the path between exchanges is worth a fortune, and hollow-core links can cut roughly a third of the delay of a glass route of the same length. Inside AI data centers, thousands of GPUs must stay tightly synchronized while shuttling enormous gradients back and forth; lower latency between racks and buildings means less idle time and more useful computation per dollar of hardware. Hollow-core fiber also carries light across a wider band of wavelengths with low loss and far less nonlinear distortion, which opens the door to packing more data channels into a single strand and pushing more power without the signal garbling itself.
Who Is Building the Industry
What was an academic curiosity is now a race between hyperscalers and the world's biggest fiber makers:
- University of Southampton - its Optoelectronics Research Centre pioneered the NANF design and set the record-low loss figures that made hollow-core viable.
- Microsoft & Lumenisity - Microsoft acquired the Southampton spinout Lumenisity and is deploying hollow-core fiber across Azure, targeting thousands of kilometers to link data centers with lower latency for cloud and AI workloads.
- Corning & OFS - the established fiber giants developing their own hollow-core products and the manufacturing lines to make them in volume.
- Sumitomo Electric - a leading Japanese fiber maker pushing record-setting low-loss hollow-core designs.
- Nokia & NKT Photonics - transporting real traffic over hollow-core links in field trials and supplying the specialty photonics that surround them.
Hollow-Core vs. Conventional Fiber
| Property | Conventional Single-Mode Fiber | Hollow-Core Fiber (NANF) |
|---|---|---|
| Light travels through | Solid glass core | Air-filled core |
| Signal speed | ~2/3 of vacuum speed | ~47% faster (near vacuum) |
| Latency | Baseline | ~30% lower |
| Signal loss | ~0.15 dB/km | Below 0.1 dB/km (record) |
| Nonlinear distortion | Present | Very low |
| Maturity & cost | Mature, cheap, everywhere | Emerging, costlier, scaling up |
The Honest Trade-Offs
Hollow-core fiber is real and carrying live traffic, but the companies scaling it are candid about the hard parts:
- Manufacturing is brutally precise. Drawing a fiber with a ring of perfectly shaped, nanometer-tuned glass tubes down its entire length is far harder than pulling a solid glass strand, and yields and volumes are only now ramping.
- Joining fibers is tricky. Splicing and connecting a hollow air core without letting in loss, dust, or moisture demands new techniques and hardware, and connecting hollow-core to the existing glass network adds complexity.
- Cost is still high. Per kilometer, hollow-core remains far more expensive than the commodity glass fiber strung across the planet, so it goes first where latency is worth a premium.
- The ecosystem is young. Amplifiers, sensors, and test gear were all built around solid glass; the surrounding toolkit for hollow-core is still being filled in.
"You will not rip out the internet and replace it with hollow-core. It shows up first on the routes where a microsecond pays for itself - between trading venues, between AI data centers, on the busiest metro links - and spreads outward from there as it gets cheaper to make."
What This Means for Business
You do not have to run a stock exchange to care about how fast light moves. Hollow-core fiber is a reminder that the network underneath every cloud application, every AI service, and every real-time experience is still being reinvented - and that latency, long treated as a fixed cost of doing business online, is now something engineers can buy down. The near-term action is not to re-cable your office, but to understand where latency actually hurts your business (real-time trading, interactive AI, live media, tightly coupled cloud workloads), to ask your connectivity and cloud providers where hollow-core and other low-latency routes are appearing, and to recognize that the same demand from AI that is reshaping chips and data centers is now reaching all the way down to the glass - or the air - that carries the light.
At Internet Pros, we help businesses make sense of fast-moving technology and turn it into a practical roadmap - from strategy to the software and automation that tie new systems together. Get in touch to talk through what emerging technology could mean for your operation, or explore more technology insights on our blog.
