Geometry Requirements for Photonic Lanterns in Spatial Division Multiplexing

We investigate using "photonic lanterns" as adiabatic mode converters for use in spatial-division multiplexing (SDM) systems to interface single-mode fibers to a multi-mode fiber. In a SDM system, minimizing the coupling loss and mode-dependent loss best utilizes all spatial modes of the fiber which increases the transmission distance, and minimizes the outage probability. We use modal analysis, the beam propagation method, and a transfer matrix technique to analyze the lanterns throughput along with its mode dependent loss and show that unitary coupling between single-mode fibers and a multi-mode fiber is only possible by optimizing the arrangements of the cores. Results include simulations of three core, 12 core, and 15 core lanterns to couple to six, 24, and 30 spatial and polarization modes.