Topological one-way Weyl fiber

Topological photonics enables unprecedented photon manipulation by realizing various topological states, such as corner, edge, and surface states. However, achieving a topological fiber state has remained elusive. Here, we demonstrate a topological fiber state in a Weyl gyromagnetic photonic crystal fiber. By applying an in-plane magnetic bias to a gyromagnetic photonic crystal fiber with broken parity-inversion symmetry, we create an asymmetrical Weyl band gap that supports one-way fiber states associated with type-II Weyl points. Dispersion and topological invariant calculations reveal a transition from Weyl surface states to one-way Weyl fiber states. Electromagnetic field simulations confirm the existence of these one-way Weyl fiber states and their robust transport, even in the presence of metallic obstacles along the transport path. Our findings offer an intriguing pathway for exploring topological states and guiding the design of topological fibers.