Topological supermodes in photonic crystal fiber

Topological states enable robust transport within disorder-rich media through integer invariants inextricably tied to the transmission of light, sound, or electrons. However, the challenge remains to exploit topological protection in a length-scalable platform such as optical fibre. We demonstrate, through both modelling and experiment, optical fibre that hosts topological supermodes across multiple light-guiding cores. We directly measure the photonic winding-number invariant characterising the bulk and observe topological guidance of visible light over metre length scales. Furthermore, the mechanical flexibility of fibre allows us to reversibly reconfigure the topological state. As the fibre is bent, we find that the edge states first lose their localization and then become relocalised due to disorder. We envision fibre as a scalable platform to explore and exploit topological effects in photonic networks.