Every moment of our lives today depends on invisible rivers of light. From video calls across continents to streaming movies, from cloud computing to the endless flow of information between data centers, the internet’s nervous system is made of glass. These glass strands—optical fibers—carry pulses of light across oceans, mountains, and cities, binding humanity in a web of instant communication.
For decades, these fibers have been marvels of human engineering. They transmit information at nearly the speed of light, with incredible reliability. But behind the smooth flow of your online life lies a stubborn limitation, one that scientists have wrestled with for over forty years: attenuation, the slow fading of light as it travels down the fiber.
Reducing this loss means signals could travel farther without needing expensive amplifiers, enabling faster, more efficient global communication. And for four decades, the world has been waiting for a breakthrough.
The 40-Year Plateau
Optical fibers rely on a core of silica glass to guide light. Silica has been pushed to its absolute limits, delivering a minimum attenuation of about 0.14 decibels per kilometer. To put that in perspective: after about 100 kilometers, much of the light signal is gone, forcing the installation of repeaters—electronic devices that amplify the signal—at regular intervals along undersea cables and terrestrial networks.
For forty years, no significant leap forward has been made in reducing this loss. Engineers tried new materials, better coatings, and innovative designs, but the plateau remained. It was as if humanity had reached a ceiling in its ability to push light through glass.
But what if glass isn’t the best medium for light at all?
A Radical Idea: Guiding Light Through Air
The speed of light in vacuum is the ultimate speed limit of the universe. Light moves slower in glass—about 30% slower than in air. If optical fibers could guide light mostly through air instead of silica, signals could not only travel faster, but also with lower loss.
This is the dream of hollow-core fibers (HCFs): fibers whose core isn’t solid glass but air, surrounded by a delicate lattice of engineered glass structures. In theory, they promised both lower attenuation and higher speed.
The problem? Reality didn’t cooperate. For decades, hollow-core fibers underperformed. Their losses were higher than silica fibers, their designs were fragile or impractical, and scaling them up for real-world use seemed impossible.
That is—until now.
A Breakthrough from Southampton
In a study published in Nature Photonics, researchers from the University of Southampton, working with Microsoft, announced a breakthrough that may change the internet forever.
They developed a new kind of hollow-core fiber, known as a nested antiresonant nodeless hollow-core fiber (DNANF). Unlike traditional fibers, its core is air, encased in a meticulously engineered microstructure of glass. The design minimizes three stubborn sources of loss—leakage of light, surface scattering, and microbending—allowing the fiber to guide light with unprecedented efficiency.
The results are nothing short of historic.
The new fiber achieves a record low attenuation of 0.091 decibels per kilometer at 1,550 nanometers, breaking past the long-standing silica record of 0.14 dB/km. Even more impressively, it maintains low losses of around 0.2 dB/km over a massive 66 terahertz bandwidth, while delivering 45% faster transmission speeds compared to conventional silica fibers.
For the first time, hollow-core fibers don’t just match silica—they surpass it.
What This Means for the Internet
The implications of this discovery ripple across the digital world. With lower losses, signals could travel longer distances without amplification, dramatically reducing the cost and energy demands of undersea cables that link continents. Data could flow faster between servers and devices, unlocking new levels of efficiency in global networks.
The study’s authors emphasize that these fibers allow low-loss transmission over a huge range of wavelengths—from 700 nm to over 2,400 nm. This means engineers can optimize communication systems around wavelengths that balance performance and cost, or even explore bands of the spectrum previously considered inaccessible.
In practical terms, this could mean:
- Faster, more energy-efficient internet connections worldwide.
- Longer unamplified spans for undersea and terrestrial communication cables.
- More reliable and cheaper data transmission.
- New opportunities in high-power laser delivery, sensing, and scientific applications.
A Glimpse of Tomorrow
The researchers are confident this is just the beginning. With further refinements—such as improving manufacturing consistency, eliminating trace absorbing gases, and refining the geometry of the fibers—they believe attenuation could fall even further, possibly to 0.01 dB/km.
That number is staggering. It would allow light to travel ten times farther without amplification, revolutionizing how we design global communication infrastructure. It could reshape the economics of the internet, cutting costs while boosting performance.
As the authors put it, these hollow-core fibers have the potential to become a “pivotal waveguiding technology,” driving the next leap in data communications.
The Human Story Behind the Light
Science is not just about numbers—it’s about vision. For decades, hollow-core fibers were an idea that looked perfect on paper but refused to work in practice. Countless researchers hit dead ends, improved designs only to see worse performance, or gave up hope of beating silica.
And yet, the work continued. The University of Southampton’s team and their partners kept refining, modeling, and testing. They built fibers up to 15 kilometers long, not just as proofs of concept, but as real-world demonstrations. They turned a fragile dream into a working technology.
It is a reminder of what science is at its best: persistence against the impossible, driven by the conviction that reality always holds deeper possibilities.
Lighting the Future
Our digital age is defined by how quickly and reliably we can move information. From artificial intelligence to virtual reality, from scientific collaboration to personal connection, everything depends on the silent streams of light racing through glass threads beneath our feet and across our oceans.
Now, a new chapter is opening. Hollow-core fibers may soon carry our voices, our data, our dreams faster and farther than ever before. What once seemed an unreachable plateau has given way to new horizons.
The future of the internet may not be written in glass after all—but in air, in light, and in the brilliance of human ingenuity.
More information: Marco Petrovich et al, Broadband optical fibre with an attenuation lower than 0.1 decibel per kilometre, Nature Photonics (2025). DOI: 10.1038/s41566-025-01747-5
