Dynamic In-Line Routing Between Distant Cores of a Multi-Core Fiber

Dynamic and coherent coupling between distant cores in a commercially available optical four-core fiber is demonstrated. Wavelength-selective excitation of cladding modes is experimentally realized by an acousto-optic mode coupler by which higher-order cladding modes are visualized and compared with simulations. By comparing the coupling conditions to a global cladding mode, the relative propagation constants of the local core modes are precisely measured at an accuracy level down to 10
^-6
. Core-cladding-core three-mode coupling operation dynamically switches optical signals between two arbitrary distant cores in the four-core fiber and achieves an inter-core switching efficiency of 55.4%.