Multicore Silica Photonic Crystal Fiber for Combined Space- and Angular-Division Multiplexing

The capacity of optical fiber communication systems is increasingly constrained by mode coupling effects in multimode fibers, limiting spatial division multiplexing (SDM) performance. To enhance SDM, novel fiber designs with low inter-core crosstalk are required. Here we theoretically investigate angular division multiplexing (ADM) in a novel multimode step-index silica multicore photonic crystal fiber (MC-PCF) with nine octagonally arranged cores. Using numerical solutions of the power flow equation, we analyze the impact of mode coupling on two- and three-channel ADM within each core, revealing that mode coupling limits the effective transmission lengths to approximately 100 m and 28 m, respectively, for a narrow launch beam. Although longer transmission distances may require further optimization of the fiber design and launch conditions, these distances are suitable for short- and medium-reach SDM/ADM systems, including data-center interconnects, laboratory networks, and other high-capacity optical links. The proposed MC-PCF exhibits significantly lower inter-core crosstalk than conventional multicore silica fibers.