Microsoft Azure scales Hollow Core Fiber (HCF) production through outsourced manufacturing

Introduction

As cloud and AI workloads surge, the pressure on datacenter (DC), Metro and Wide Area Network (WAN) networks has never been greater. Microsoft is tackling the physical limits of traditional networking head-on. From pioneering research in microLED technologies to deploying Hollow Core Fiber (HCF) at global scale, Microsoft is reimagining connectivity to power the next era of cloud networking.

Azure’s HCF journey has been one of relentless innovation, collaboration, and a vision to redefine the physical layer of the cloud. Microsoft’s HCF, based on the proprietary Double Nested Antiresonant Nodeless Fiber (DNANF) design, delivers up to 47% faster data transmission and approximately 33% lower latency compared to conventional Single Mode Fiber (SMF), bringing significant advantages to the network that powers Azure.

Today, Microsoft is announcing a major milestone: the industrial scale-up of HCF production, powered by new strategic manufacturing collaborations with Corning Incorporated (Corning) and Heraeus Covantics (Heraeus). These collaborations will enable Azure to increase the global fiber production of HCF to meet the demands of the growing network infrastructure, advancing the performance and reliability customers expect for cloud and AI workloads.

Figure 1: Examples of HCF during the manufacturing process

Real-world benefits for Azure customers

Since 2023, Microsoft has deployed HCF across multiple Azure regions, with production links meeting performance and reliability targets. As manufacturing scales, Azure plans to expand deployment of the full end-to-end HCF network solution to help increase capacity, resiliency, and speed for customers, with the potential to set new benchmarks for latency and efficiency in fiber infrastructure.

Why it matters

Microsoft’s proprietary HCF design brings the following improvements for Azure customers:

• Increased data transmission speeds with up to 33% lower latency.
• Enhanced signal performance that improves data transmission quality for customers.
• Improved optical efficiency resulting in higher bandwidth rates compared to conventional fiber.

How Microsoft is making it possible

To operationalize HCF across Azure with production grade performance, Microsoft is:

• Deploying a standardized HCF solution with end-to-end systems and components for operational efficiency, streamlined network management, and reliable connectivity across Azure’s infrastructure.
• Ensuring interoperability with standard SMF environments, enabling seamless integration with existing optical infrastructure in the network for faster deployment and scalable growth.
• Creating a multinational production supply chain to scale next generation fiber production, ensuring the volumes and speed to market needed for widespread HCF deployment across the Azure network.

Scaling up and out

With Corning and Heraeus as Microsoft’s first HCF manufacturing collaborators, Azure plans to accelerate deployment to meet surging demand for high-performance connectivity. These collaborations underscore Microsoft’s commitment to enhancing its global infrastructure and delivering a reliable customer experience. They also reinforce Azure’s continued investment in deploying HCF, with a vision for this technology to potentially set the global benchmark for high-capacity fiber innovation.

“This milestone marks a new chapter in reimagining the cloud’s physical layer. Our collaborations with Corning and Heraeus establish a resilient, global HCF supply chain so Azure can deliver a standardized, world-class customer experience with ultra-low latency and high reliability for modern AI and cloud workloads.” - Jamie Gaudette, Partner Cloud Network Engineering Manager at Microsoft

Figure 2: HCF winding onto a spool during the manufacturing process

To scale HCF production, Microsoft will utilize Corning’s established U.S. facilities, while Heraeus will produce out of its sites in both Europe and the U.S.

"Corning is excited to expand our longtime collaboration with Microsoft, leveraging Corning’s fiber and cable manufacturing facilities in North Carolina to accelerate the production of Microsoft's Hollow Core Fiber. This collaboration not only strengthens our existing relationship but also underscores our commitment to advancing U.S. leadership in AI innovation and infrastructure. By working closely with Microsoft, we are poised to deliver solutions that meet the demands of AI workloads, setting new benchmarks for speed and efficiency in fiber infrastructure." - Mike O'Day, Senior Vice President and General Manager, Corning Optical Communications

“We started our work on HCF a decade ago, teamed up with the Optoelectronics Research Centre (ORC) at the University of Southampton and then with Lumenisity prior to its acquisition. Now, we are excited to continue working with Microsoft on shaping the datacom industry. With leading solutions in glass, tube, preform, and fiber manufacturing, we are ready to scale this disruptive HCF technology to significant volumes. We’ll leverage our proven track record of taking glass and fiber innovations from the lab to widespread adoption, just as we did in the telecom industry, where approximately 2 billion kilometers of fiber are made using Heraeus products.” - Dr. Jan Vydra, Executive Vice President Fiber Optics, Heraeus Covantics

Azure engineers are working alongside Corning and Heraeus to operationalize Microsoft manufacturing process intellectual property (IP), deliver targeted training programs, and drive the yield, metrology, and reliability improvements required for scaled production.

The collaborations are foundational to a growing standardized, global ecosystem that supports:

• Glass preform/tubing supply
• Fiber production at scale
• Cable and connectivity for deployment into carrier‑grade environments

Building on a foundation of innovation: Microsoft’s HCF program

In 2022, Microsoft acquired Lumenisity, a spin‑out from the Optoelectronics Research Centre (ORC) at the University of Southampton, UK. That same year, Microsoft launched the world’s first state‑of‑the‑art HCF fabrication facility in the UK to expand production and drive innovation. This purpose-built site continues to support long‑term HCF research, prototyping, and testing, ensuring that Azure remains at the forefront of HCF technology.

Figure 3: A) Preparing HCF to splice in the lab B) World’s first HCF fabrication facility located in the UK C) Testing in Azure Fiber’s Systems lab

Working with industry leaders, Microsoft has developed a proven end‑to‑end ecosystem of components, equipment, and HCF‑specific hardware necessary and successfully proven in production deployments and operations. 

Pushing the boundaries: recent breakthrough research

Today, the University of Southampton announced a landmark achievement in optical communications: in collaboration with Azure Fiber researchers, they have demonstrated the lowest signal loss ever recorded for optical fibers (<0.1 dB/km) using research-grade DNANF HCF technology (see figure 4). This breakthrough, detailed in a research paper published in Nature Photonics earlier this month, paves the way for a potential revolution in the field, enabling unprecedented data transmission capacities and longer unamplified spans.

Figure 4: (Left) Cross section of DNANF HCF (Right) Comparing loss (dB/km) from this HCF research with previous solid glass fiber (PSCFs) loss records at around 1550nm [1] 2002 Nagayama et al.¹[2] 2025 Sato et al.² [3] 2025 research-grade DNANF HCF Petrovich et al.³

This breakthrough highlights the potential for this technology to transform global internet infrastructure and DC connectivity. Expected benefits include:

• Faster: Approximately 47% faster, reducing latency, powering real-time AI inference, cloud gaming and other interactive workloads.
• More capacity: A wider optical spectrum window enabling exponentially greater bandwidth.
• Future-ready: Lays the groundwork for quantum-safe links, quantum computing infrastructure, advanced sensing, and remote laser delivery.

Looking ahead: Unlocking the future of cloud networking

The future of cloud networking is being built today! With record-breaking^[3] fiber innovations, a rapidly expanding collaborative ecosystem, and the industrialized scale to deliver next-generation performance, Azure continues to evolve to meet the demands for speed, reliability, and connectivity. As we accelerate the deployment of HCF across our global network, we’re not just keeping pace with the demands of AI and cloud, we’re redefining what’s possible.

References:

[1] Nagayama, K., Kakui, M., Matsui, M., Saitoh, T. & Chigusa, Y. Ultra-low-loss (0.1484 dB/km) pure silica core fibre and extension of transmission distance. Electron. Lett. 38, 1168–1169 (2002).

[2] Sato, S., Kawaguchi, Y., Sakuma, H., Haruna, T. & Hasegawa, T. Record low loss optical fiber with 0.1397 dB/km. In Proc. Optical Fiber Communication Conference (OFC) 2024 Tu2E.1 (Optica Publishing Group, 2024).

[3] Petrovich, M., Numkam Fokoua, E., Chen, Y., Sakr, H., Isa Adamu, A., Hassan, R., Wu, D., Fatobene Ando, R., Papadimopoulos, A., Sandoghchi, S., Jasion, G., & Poletti, F. Broadband optical fibre with an attenuation lower than 0.1 decibel per kilometre. Nat. Photon. (2025). https://doi.org/10.1038/s41566-025-01747-5

Useful Links:

• The Deployment of Hollow Core Fiber (HCF) in Azure’s Network
• How hollow core fiber is accelerating AI   | Microsoft Azure Blog
• Learn more about Microsoft global infrastructure