Generation and characterization of tunable optical skyrmions in mode-division-multiplexing fibers

Mode-division-multiplexing (MDM) technology in few-mode optical fibers offers new opportunities for advancing topological optics. In this Letter, we report, for the first time to our knowledge, the generation of tunable skyrmions in an MDM fiber. We also propose a direct and precise method for identifying the coefficients of the modes that constitute skyrmions and reconstructing the expected topological textures using only intensity images in experiments. Our work contributes to the development of novel generation schemes and accurate characterization for skyrmions.