Twisting optical fiber creates a robust new pathway for light

Light powers everything from communications to sensing, yet even tiny imperfections can scatter it and weaken signals. To address this, a team led by the University of Bath in the UK – working with the University of Cambridge and international partners – has developed a new structure that keeps light flowing smoothly even through bends, twists or damage, with the potential to operate over unprecedented distances.

This new fibre‑based photonic topological insulator provides protected pathways that keeps light flowing in the intended direction rather than scattering.

These features make it a strong candidate for:

• The ultra-reliable light‑based connections needed to transmit data between chips, devices or electronic components, and
• Directing light signals in advanced communications (such as high-bandwidth or even quantum communications), precision sensing (including in medical imaging and environmental monitoring) and emerging quantum technologies, where uninterrupted, stable light flow is essential.

The researchers found that by using standard telecom‑grade materials to create an optical fibre with multiple light‑guiding cores, and then introducing a simple twist during fabrication, they could form a pathway that remains resilient to defects and disorder, ensuring light continues to propagate smoothly.

Their study is published today in the prestigious journal Nature Photonics.

Robust signal transmission

Conventional optical fibre used in telecommunications guides light along a single core, allowing it to travel freely in two directions – forwards and backwards. Any tiny imperfection in the glass 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.

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.

The new twisted fibre avoids these problems. Its 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, signal transmission has the potential to be far more robust.

Because the twist is added during the normal manufacturing steps that fibre fabricators already use, no special processing is required. The resulting fibre therefore shares many of the characteristics of a standard optical fibre. It:

• Can be produced in extended lengths – unlike existing materials used for topological insulators, which are typically limited to small pieces of solid material
• Remains flexible
• Transmits light with minimal loss

In short, this technique is fully compatible with existing fibre‑production methods while adding resilience to defects.

State-of-the-art optical labs

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 labs.

Study co‑author Dr Peter Mosley, from the Department of Physics at Bath, said: “By adding a controlled twist as the fibre is created, we’re able to induce topological behaviour that lets light flow around defects rather than scatter from them. It’s a clean, scalable way to build robustness into photonic interconnects.

“This is the first demonstration of an optical fibre with two-dimensional topologically protected light guidance. 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.”

Dr Anton Souslov, associate professor at the Cavendish Laboratory at the University of Cambridge and study co‑author said: “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.”

ENDS.