Twisting-Rate-Controlled 125 μm Cladding Randomly Coupled Single-Mode 12-Core Fiber

A multicore fiber design with more than 10 coupled cores is investigated numerically and experimentally. It is revealed that a randomly coupled 12-core structure with a square lattice core arrangement can be realized within a 125 μm cladding by employing fiber twisting of more than a few π rad/m. A 125 μm-clad twisting-rate-controlled 12-core fiber is then fabricated and a relative core density of 12 compared with conventional single-mode fiber is achieved while maintaining a low spatial mode dispersion characteristic of 8.4 ps/√km at 1550 nm. Finally, we experimentally evaluated the performance of 12 spatial channels by conducting a 24 × 24 MIMO transmission experiment.