Southampton achieves ‘record’ low signal loss with hollow fiber

06 Oct 2025

Based on fiber that guides light through core of air; achieves “lowest ever” signal loss.

Researchers from the University of Southampton have developed a novel optical fiber design that demonstrates significant improvements in speed, efficiency, and data capacity. The design was developed with collaboration from Microsoft Azure Fiber.

Described in a paper in Nature Photonics, the development introduces a fiber that guides light through a hollow core of air, rather than traditional solid glass, achieving the lowest signal loss ever recorded and enabling faster, more energy-efficient data transmission over long distances.

“This is a breakthrough in how we transmit information,” said Professor Francesco Poletti, Professorial Fellow at the University of Southampton and Chief Scientist at Microsoft Azure Fiber.

“For decades, the performance of optical fibers has remained largely unchanged. This new fiber design breaks through that barrier, demonstrating the potential for faster data transmission, lower energy use, and the ability to carry much more data. It’s a fundamental shift in global connectivity. This result is the pinnacle of over 10 years of research and development, made possible by the ingenuity, collaboration and dedication of an interdisciplinary team working across Microsoft and the University of Southampton,” Prof. Poletti said.

At the heart of this innovation is the Double Nested Antiresonant Nodeless Hollow Core Fiber (DNANF), a sophisticated structure invented by researchers at the Optoelectronics Research Centre (ORC) at the University of Southampton and Microsoft Azure Fiber. These fibers feature a central hollow core surrounded by ultra-thin glass membranes arranged in nested layers, and allow light to travel primarily through air, dramatically reducing the scattering and absorption that limit conventional fibers.

To put this in perspective: in the new DNANF fiber, light can travel 33km before its power is reduced by half. In contrast, standard telecom fibers, typically with a loss of around 0.2 dB/km, reach only 15km before experiencing the same reduction. This means the new fiber can more than double the transmission distance without needing amplification, unlocking the potential to cut future energy use and infrastructure costs.

“These advances in ultra-low-loss HCF will let Microsoft transmit more data with less power and dramatically lower latency across our global network,” said Jamie Gaudette, Partner Network Engineering Manager at Microsoft. “Together, with the team at the University of Southampton, Azure is redefining the physical layer to deliver a faster, more reliable and cost-efficient cloud experience to Customers worldwide.”

Key features of the technology

The Southampton announcements list the following features and capabilities of the hollow core optical fiber – if and when it may be deployed at scale:

• Faster: Approximately 47% faster, reducing latency, powering real-time AI inference, cloud gaming and other interactive workloads.
• Greener: lower signal loss means fewer amplifiers, cutting energy use and carbon footprint.
• More Capacity: A wider optical spectrum window enables exponentially greater bandwidth.
• Future-Ready: Lays the groundwork for quantum-secure links, quantum computing infrastructure, advanced sensing and remote laser delivery.

For more than 40 years, traditional glass-based fibers have been constrained by how much light they lose over long distances. DNANF fibers change that paradigm. By guiding light through air with unprecedented precision, they offer ultra-low loss across a wide range of wavelengths, more than double the usable spectrum of conventional fibers. The researchers believe this technology could become the backbone of future internet infrastructure, while also transforming data centre connectivity and cloud services.