In an effort to boost data transmission speed in its cloud, Microsoft has inked manufacturing agreements with Corning and Germany’s Heraeus to scale production of hollow-core fiber (HCF), a next-generation optical medium it has begun deploying across Azure to curb latency for AI and cloud workloads.
The deals formalize what Microsoft signaled after its 2022 acquisition of U.K.-based HCF maker Lumenisity: HCF is no longer a lab curiosity but an element of Azure’s physical layer. Corning will build Microsoft’s HCF at its North Carolina facilities, and Heraeus will produce in Europe and the U.S., creating a multi-region supply chain aimed at consistent global rollouts.
The HCF Advantage
HCF differs fundamentally from today’s single-mode fiber. Instead of guiding photons through solid glass, HCF routes light through an air-filled core encircled by a glass lattice. Less glass in the path reduces dispersion and trims latency. Microsoft says its proprietary Double Nested Antiresonant Nodeless Fiber (DNANF) design delivers up to 47% faster transmission and about 33% lower latency than conventional single-mode fiber in its tests. The company began live deployments after acquiring Lumenisity and says the fiber has been lighting up multiple Azure regions since 2023.
The market demand is compelling: modern AI services are voracious for bandwidth but even more sensitive to delay. Shaving milliseconds between models, storage, and accelerators can compound into meaningful application performance gains.
For Corning, a leader in optical glass, the program is both a manufacturing challenge and a validation of HCF’s readiness. The company said it is collaborating with Azure engineers to operationalize Microsoft’s processes on high-volume lines, and to evolve next-generation manufacturing platforms that push yields, performance, and quality. The scope goes beyond fiber: the collaboration includes cable and connectivity products to deliver end-to-end assemblies fit for Azure data center environments.
Heraeus, known for quartz and fused-silica products in photonics and telecom, brings additional capacity and materials expertise. Together, the two vendors give Microsoft geographic redundancy and a path to expand output without relying on a single plant or region, which matters as Azure’s buildout supports AI demand across continents.
While HCF won’t displace single-mode fiber everywhere—glass remains cost-effective and deeply entrenched—select, latency-critical data networks inside and between data centers are ripe candidates for HCF’s characteristics.
Customer Benefit?
In terms of benefits for customers, there’s nothing immediate at the configuration level. But the cumulative effect of HCF can surface due to faster inference, tighter synchronization across GPU clusters, and more predictable performance for latency-sensitive services. That predictability matters as Microsoft layers agentic AI and real-time features on top of its cloud.
The partnerships also show how cloud providers increasingly co-design infrastructure with manufacturers. Microsoft supplies the reference design and operational requirements, then partners scale them with industrial rigor.
There are, to be sure, open questions. How broadly will HCF be economical across metro and long-haul routes? What does repair and field tooling look like at scale? Microsoft isn’t positioning HCF as a universal replacement so much as a targeted accelerant where microseconds move the needle. Given the many markets that Microsoft competes in, those pockets are expanding.
Taken together, the Corning and Heraeus deals are less a marketing flourish than a supply-chain commitment. Given that Azure intends to be an AI-first platform, the network underneath must keep pace. HCF is Microsoft’s answer for the segments where glass has become the bottleneck—and where shaving delay is now a competitive feature, not a nice-to-have.
