Researchers at the University of Bath have developed a new design for optical fibres to make them more robust.
Bending or twisting fibres can lead to light leaking out with a loss of data. The technique developed by the Bath team deploys topological ideas by including several light-guiding cores in a fibre, linked together in a spiral. Light can hop between these cores but becomes trapped within the edge thanks to the topological design. These edge states are protected against disorder in the structure.
“Whenever you fabricate a fibre-optic cable, small variations in the physical structure of the fibre are inevitably present. When deployed in a network, the fibre can also get twisted and bent. One way to counter these variations and defects is to ensure the fibre design process includes a real focus on robustness. This is where we found the ideas of topology useful,” said said Physics PhD student Nathan Roberts, who led the research.
The multicore structure forms the platform for a topological photonic crystal fibre (TopoPCF) that translates the strategies for topological band engineering into fibre. Fabricating the TopoPCF gives visibility of the propagation of edge states with visible light and bending for topological mode control. Bending the fibre leads to an effective disorder inside the topological state, which can be switched on and off through mechanical reconfiguration.
“Using our fibre, light is less influenced by environmental disorder than it would be in an equivalent system lacking topological design,” said Bath physicist Dr Anton Souslov, who co-authored the study as theory lead. “By adopting optical fibres with topological design, researchers will have the tools to pre-empt and forestall signal-degrading effects by building inherently robust photonic systems.”
Quantum networks are expected to play an important technological role in years to come. But the quantum states of light that transmit information are easily impacted by their environment and finding a way to protect them is a major challenge. This work may be a step towards maintaining quantum information in fibre optics using topological design.
“We have shown that you can make kilometres of topological fibre wound around a spool. We envision a quantum internet where information will be transmitted robustly across continents using topological principles,” said Roberts.
He pointed out that this research has implications that go beyond communications networks. “Fibre development is not only a technological challenge, but also an exciting scientific field in its own right Understanding how to engineer optical fibre has led to light sources from bright ‘supercontinuum’ that spans the entire visible spectrum right down to quantum light sources that produce individual photons – single particles of light.”