Single-mode chirally-coupled-core fibers with larger than 50 µm diameter cores.

In this paper, we report an advance in increasing core size of effective single-mode chirally-coupled-core (CCC) Ge-doped and Yb-doped double-clad fibers into 55 µm to 60 µm range, and experimentally demonstrate their robust single-mode performance. Theoretical and numerical description of CCC fibers structures with multiple side cores and polygon-shaped central core is consistent with experimental results. Detailed experimental characterization of 55 µm-core CCC fibers based on spatially and spectrally resolved broadband measurements (S(2) technique) shows that modal performance of these large core fibers well exceeds that of standard 20 μm core step-index large mode area fibers.