Hollow-Core Fiber Hits the Field: The First Commercial Deployments Are Live

Hollow-core fiber spent twenty years as one of the most promising and consistently almost-ready technologies in telecommunications. The concept was elegant: instead of transmitting light through glass, transmit it through air, where it moves at nearly the vacuum speed of light rather than the roughly two-thirds fraction achievable in silica. The practical engineering was brutally hard. By October 2026, it has been solved well enough that hollow-core fiber is no longer a research story. It is a procurement story, with purchase orders, cable plants and installation crews attached.

The clearest marker is Microsoft. The company bought Lumenisity, the University of Southampton spin-out, in 2022, and its Azure Fiber group in Romsey, England, has since turned the double nested antiresonant nodeless fiber design into a production product. Microsoft's Nature paper in September 2025 reported attenuation of 0.091 dB per kilometer at 1550 nm, below the 0.14 dB per kilometer floor of the best solid-core silica fiber, and that result flipped the industry conversation from whether hollow-core could ever match glass to how quickly it could be made in volume. Microsoft says it has already deployed around 1,280 kilometers of hollow-core fiber carrying live Azure traffic, including a dual-route interconnect between two European data centers using hybrid cables with 32 hollow-core strands alongside 48 standard single-mode fibers. Its stated plan, announced in late 2024, was 15,000 kilometers across the Azure network over two years, and the manufacturing moves of the past twelve months are what make that number credible.