The Azure team’s breakthrough, tested over 1,200 km of fiber, cuts transmission loss to below 0.1 dB/km and expands bandwidth, promising faster, cheaper, and more energy-efficient data networks.
Microsoft has achieved a breakthrough in the hollow core fiber technology, reducing data transmission loss to just 0.091 dB per kilometer, the lowest ever achieved and significantly below the 0.14 dB/km limit that has constrained fiber networks for decades.
The research, published in Nature Photonics by scientists at Microsoft Azure Fiber in Romsey, UK, and the University of Southampton, demonstrated the first optical fiber to outperform conventional glass-core fibers in both signal loss and bandwidth capacity.
Microsoft’s hollow core fiber experiment maintained a loss of below 0.1 dB per km across an 18 THz bandwidth and operated with less than 0.2 dB per km loss across a 66 THz window when manufacturing impurities were eliminated.
“Although this was a pilot project, it involved over 1,200 km of fibre, now installed underground and actively carrying live traffic,” Francesco Poletti, partner researcher at Microsoft Azure, told Network World. Microsoft CEO Satya Nadella announced at the company’s 2024 Ignite conference that 15,000 km of hollow core fiber would be deployed across the Azure network in the coming months, he added.
Microsoft is already deploying the technology at scale
The achievement represents a significant advancement since Microsoft’s December 2022 acquisition of Lumenisity Limited, a University of Southampton spin-out that had developed early hollow core fiber technology. When Microsoft acquired Lumenisity, the company’s hollow core fibers achieved around 2.5 dB/km loss – better than previous hollow core attempts but still far worse than traditional glass fibers at 0.14 dB/km.
Microsoft’s acquisition included Lumenisity’s 40,000-square-foot manufacturing facility in Romsey, UK, described as the world’s first dedicated hollow core fiber production plant. However, the technology needed substantial improvement to become commercially viable against established glass fiber networks.
The breakthrough published in Nature Photonics shows Microsoft’s researchers improved the technology dramatically, achieving 0.091 dB/km – more than 25 times better than the acquired technology and, for the first time, better than traditional glass fibers.
Breaking through decades-old limitations
The significance of Microsoft’s achievement becomes clear when compared to the industry’s struggle with fiber performance limits. Traditional silica glass fibers have hit a performance wall.
“Despite unrelented progress in the field of optical communications since 1970, the minimum attenuation of silica glass fibres has remained approximately unchanged,” the researchers wrote in their paper, noting that losses improved only marginally from 0.154 dB/km in 1985 to 0.1396 dB/km in 2024.
The hollow core approach uses air as the transmission medium, surrounded by a precisely engineered glass microstructure. This design allows light to travel 47% faster while maintaining signal quality. “This approach not only reduces attenuation and other signal degradation phenomena, but it also increases transmission speeds by 45%,” according to the research paper.
The technology also delivered a seven-fold reduction in chromatic dispersion compared to conventional fibers. The paper noted this “enables simplifications in the transceiver’s digital signal processing complexity and energy consumption” for coherent transmission systems.
Potential for significant cost savings
The improved performance could translate to substantial cost reductions for enterprise networks. Poletti said the technology’s lower signal loss means networks can extend distances between expensive amplifiers or operate existing amplifiers at reduced power levels.
“It is entirely plausible that future network architectures could skip one in every two or three amplifier sites, resulting in significant reductions in both capital expenditure and operational expenditure,” Poletti explained.
The reduced chromatic dispersion also simplifies equipment requirements. “The fibres’ 6–7x lower chromatic dispersion enables simplification of the transceiver’s digital signal processing, contributing to both reduced complexity and operational power consumption,” he added.
Industry validation through trials and deployments
Microsoft wasn’t the only company to recognize the technology’s potential. Other major operators tested the technology independently before Microsoft’s large-scale deployment.
Comcast became the first US internet service provider to deploy hollow core fiber end-to-end in April 2022, implementing a 40-kilometer connection in Philadelphia. The company reported data traveled 150% faster with 33% lower latency compared to traditional fiber.
BT conducted trials using 10-kilometer lengths at its research facility for 5G networks and quantum communications applications. European network provider euNetworks deployed the technology commercially on a 45-kilometer route between London data centers.
Manufacturing challenges remain
Despite these successful trials and Microsoft’s commercial deployment, volume production faces significant hurdles. “While the same general fabrication equipment used for conventional all-glass fibres is employed, the manufacturing processes for HCF are fundamentally different,” Poletti said. “This necessitates the development of custom machinery to enable full automation.”
The manufacturing process requires precise control of membrane thicknesses around 500 nanometers. The complex nested tube design adds complexity compared to conventional fiber production, though Microsoft is leveraging its resources to address scaling challenges, he added.
“Financial trading was the earliest sector to benefit, with its well-funded operators contributing to the initial development of the technology,” Poletti noted.
Applications are expanding to other high-value segments. “A likely next phase of adoption could involve enhancing the efficiency of AI workloads and enabling more flexible regional placement of data centres,” Poletti said.
Market availability timeline
Microsoft deployed the technology first, but broader industry access appears likely as production scales. “Microsoft was the first to recognize the potential of the technology and to place its trust in it, taking on the initial development risks,” Poletti said. “However, it is reasonable to anticipate that, over time, the technology will reach the broader market and deliver benefits across the entire telecommunications and data communications ecosystem.”
The research showed the technology could operate across wavelengths from 700 nm to over 2,400 nm, potentially enabling much broader bandwidth applications than current telecommunications systems. Modeling suggested optimized designs could achieve even lower losses of 0.018 dB/km with larger core designs.
Industry transformation potential
The researchers concluded their paper by stating the breakthrough “has the potential to enable the next technological leap in data communications.” For enterprise networks facing growing bandwidth demands from AI workloads and digital transformation, the technology offers performance improvements that seemed impossible just years ago.
“If we succeed in scaling up production, reducing manufacturing costs, and fostering a robust ecosystem, we believe HCFs have the potential to transform the entire telecommunications industry,” Poletti said.
