Microsoft-backed researchers say they’ve cut optical-fiber signal loss to a level never seen before, a milestone that—if it holds up at scale—could reshape how cloud providers move data and how quickly the rest of us experience the Internet.
In a paper published this week in Nature Photonics, a team linked to Microsoft Azure Fiber and the UK’s University of Southampton reports an attenuation of 0.091 dB per kilometer in a new hollow-core fiber design. For decades, the practical floor for conventional glass-core fiber has hovered around the slower 0.14 dB/km rate. Crossing under that level with a hollow, air-filled core offers more than bragging rights: it means signals travel farther before they need amplification, trimming cost and energy use across data networks.
“This breakthrough result paves the way for a potential revolution in optical communications, enabling unprecedented data transmission capacities, more energy-efficient optical networks and longer unamplified spans,” the research team wrote in its published paper.
Air Is Faster Than Glass
Speed is a key benefit here. Because light moves faster in air than in glass, hollow-core designs promise lower latency. The team claims up to 45 percent faster transmission versus today’s silica-core cables, which are made from glass. That kind of latency reduction is significant for workloads where milliseconds are a big deal. Examples include AI data speeding between data centers, stock trading, and remote surgery.
Microsoft says a 1,200-kilometer pilot carried data with loss under 0.1 dB/km across an 18-THz span, and under 0.2 dB/km loss across 66-THz when manufacturing impurities were scrubbed. The company is already leaning in operationally. After acquiring hollow-core pioneer Lumenisity in 2022, including its 40,000-square-foot production facility in Romsey, U.K., Microsoft is preparing broader rollout. The company has plans to lay thousands of kilometers of hollow-core in its Azure backbone.
Hollow-core isn’t a new idea, and other companies have trialed the technology. But earlier versions faced challenges, including leakage of light. The latest advance refines a geometry known as double-nested anti-resonant nodeless fiber (DNANF). It uses a hair-thin, air tunnel girded by ultra-fine glass membranes that steer photons around the core instead of through it.
The difficulty is keeping those membranes precisely formed and clean. As fabrication improved, loss dropped, and with it the need for frequent optical amplifiers. Fewer amplifiers translate to lower cost, less power needed, and simpler maintenance.
The Road Ahead
This technology remains nascent. Manufacturing yield, splice reliability, and connector standards all need to mature before enterprise networks can invest seriously. The team’s best-case 0.091 dB/km was a peak result, and large-scale deployment will require repeatability. Industry standardization typically takes years, and carriers will want multi-vendor ecosystems before committing their network backbone.
The near-term play appears to be: Azure uses the fiber internally, where a single buyer controls routes, equipment, and risk. If performance meets expectations, expect hollow-core to gain adoption in metro rings and cloud regions next. Over time, mobile networks stand to gain as backhaul tightens under 5G/6G data.
Long term, the direction seems clear. For an industry wrestling with AI-driven growth and rising power bills, shaving loss below glass while cutting latency is real accomplishment. If vendors can manufacture at volume and standards bodies move briskly, the fiber that carries the world’s bits may soon be more air than glass. Hollow-core now looks less like a science project and more like a pragmatic path to speed and efficiency.
