Fibre Twist Creates A New Pathway For Light

A team of researchers from University of Cambridge, University of Bath and international collaborators, have designed a new optical fibre structure that keeps light flowing smoothly even through bends, twists or structural imperfections. This development could enable ultra-reliable communications, precision sensing and emerging quantum technologies by reducing signal loss over long distances.

“Topological states of light have many potential uses in communications and quantum technologies, and it is exciting to see them realised in such a scalable and ready-to-use platform as optical fibre. Going forward, I am especially interested in the variety of yet-unexplored topological phenomena that optical fibre is uniquely able to demonstrate.”- Anton Souslov

Light powers everything from communications to sensing, yet even tiny imperfections can scatter it and weaken signals.

In the new study, published in Nature Photonics, researchers have addressed this challenge by developing an optical fibre with several light-guiding cores (the central paths that light travels through) made from standard telecommunications materials.

Conventional optical fibre guides light along a single core. This allows light to travel freely in two directions: forwards and backwards. Any tiny imperfection in the core can scatter the light, either leaking it out of the fibre or reflecting it backwards from the intended direction of travel. This can degrade or even destroy the signal.

Scientists have tried adding more cores to carry more data at once. Adding more cores can, in principle, create additional channels for carrying more data but, in practice, light tends to ‘couple’ between neighbouring cores. This mixes channels, introduces noise and limits how much information a multi‑core fibre can reliably carry.

In contrast, this new fibre-based photonic topological insulator provides protected pathways that keeps light flowing in the intended direction rather than scattering. This makes the fibre analogous to electronic topological insulators, in which flow is restricted only to the edge.

“The new fibre solves the problem in a surprisingly simple way,” explains co-author Dr Peter Mosley from the Department of Physics at the University of Bath. “By introducing a controlled twist during fibre fabrication, we induce topological behaviour that creates special pathways to keep light locked on course, allowing it to flow around defects rather than scatter from them. It’s a clean, scalable way to strengthen photonic interconnects.”

The new twisted fibre’s many cores, combined with a built-in twist, creates special protected states of light that naturally follow the twist and avoid coupling into other cores. When the light meets a defect, it simply flows around it instead of scattering. As a result, it makes signal transmission potentially far more robust.

Following extensive design and simulation work, the topological fibre was fabricated in the Centre for Photonics at the University of Bath and tested in the university’s state-of-the-art optics laboratories.

“This is the first demonstration of an optical fibre with two-dimensional topologically protected light guidance,” said Mosley. “Even though we used only short lengths of fibre for this demonstration, our work shows a path toward protecting signals in mass-produced optical fibres that could be used in large data-centre networks.”

The twist is integrated into the standard manufacturing steps already used by fibre fabricators, so no special processing is required. As a result, the fibre retains many of the advantages of a conventional optical fibre. Unlike existing materials used for topological insulators, which are typically limited to small pieces of solid material, the fibre can be produced in extended lengths, remains flexible, and transmits light with minimal loss.

This technique is fully compatible with existing fibre-production methods while adding resilience to defects. These features make it a strong candidate for the ultra-reliable light-based connections needed to transmit data between chips, devices and electronic components, as well as for directing light signals in advanced communications, precision sensing applications and emerging quantum technologies where uninterrupted, stable light flow is essential.

“Topological states of light have many potential uses in communications and quantum technologies, and it is exciting to see them realised in such a scalable and ready-to-use platform as optical fibre. Going forward, I am especially interested in the variety of yet-unexplored topological phenomena that optical fibre is uniquely able to demonstrate,” said Dr Anton Souslov, Associate Professor at the Cavendish Laboratory, University of Cambridge, and study co-author.