The next internet revolution may come through a hollow strand of glass.
Instead of the solid glass cores that dominate today’s internet cables, researchers at the University of Southampton have developed a fiber that guides light through tiny air-filled channels.
By letting signals travel through air rather than glass, the design reduces energy loss and allows light to move more efficiently over long distances.
In conventional fibers, about half the signal is lost every 15–20 kilometers, requiring frequent relay stations to boost and retransmit data.
The new hollow design extends that distance to around 33 kilometers before losing half the light.
“If new technology comes along and says you can skip one building every two or three, that’s a very significant cost saving,” explained lead researcher Francesco Poletti.
The fibers can also carry more than 1,000 times the power of conventional versions and transmit signals across a broader range of wavelengths.
That includes single-photon pulses of visible light, which are typically used in quantum communication systems. This dual capability makes the breakthrough significant not only for existing networks but also for emerging quantum technologies.
Faster highways for data
Hollow optical fibers are not entirely new. Previous designs have been used in specialized applications, such as connecting computing units inside data centers where speed is critical.
Because light travels about 45 percent faster through air than through glass, hollow fibers offer an immediate advantage. But until now, they have been too costly or impractical for wide-scale deployment.
Poletti, a photonics and materials-science researcher at Southampton, has been refining this particular design for more than ten years.
The key lies in its unique structure: five small cylinders, each containing two nested cylinders, are attached to the rim of one larger cylinder.
This precise arrangement ensures that only specific wavelengths of light fit within the hollow core, keeping pulses tightly confined instead of leaking away. “We really think this could be transformative,” Poletti said.
From lab to market
The challenge has been to manufacture these fibers at scale without losing their delicate geometry.
Conventional optical fibers are made by melting and stretching solid glass into thin strands. In contrast, the Southampton team starts with a larger glass preform about 20 centimeters wide, with the hollow channels already built in.
As the fiber is stretched down to about 100 micrometers in diameter, the hollow spaces are pressurized to preserve the structure.
Commercialization is already underway. Lumenisity will produce the fibers, a start-up spun out of Southampton.
Microsoft acquired the company in 2022, underscoring industry interest in the technology’s potential. If the fibers prove durable and cost-effective, they could make today’s telecommunications systems faster and cheaper while also supporting the next generation of quantum communication networks.
“This result is very interesting for the quantum communication community,” said Tracy Northup, an experimental physicist at the University of Innsbruck in Austria.
Until now, hollow fibers have been prohibitively expensive even for small-scale laboratory experiments, she noted. “We in the research community can hope that scaled-up production may bring prices down significantly in the future.”