Few-mode multicore fibers for long-haul transmission line

•Designee issues in FM-MCFs are presented.•Proposed FM-MCFs to date are reviewed.•Design and measured characteristics of a fabricated FM-MCF are presented.

Few-mode multicore fibers (FM-MCFs) that enable dense space-division multiplexing (DSDM) have the potential to drastically improve the fiber capacity. In designing the FM-MCFs, several issues that originate from multicore fibers and few-mode fibers must be considered. In this paper, these design issues such as inter-core crosstalk (IC-XT) and dispersion mode delay (DMD) are discussed. A three-mode 12-core fiber with low-DMD low-IC-XT achieves long-haul DSDM transmission over 500 km. The design concept, fiber design, and characteristics of the fabricated three-mode 12-core fiber are also described.