Multiplexing Coupler Realized with Y-branched GI Core Polymer Optical Waveguide for Mode Division Multiplexing in a $50-\mu \mathrm{m}$ Multimode Fiber

In this paper, a novel structure for a multimode Y-branched polymer waveguide type multiplexer (MUX) device for mode division multiplexing (MDM) is proposed. Since the insertion loss of GI core Y-branched waveguides remains low even with the tilted launch beam or a small size of cross-sectional core, we have proposed asymmetric Y-branched MUX device which has different core size at the end of two-port arm. In this paper, we investigate the optimum structure of the asymmetric Y-branched waveguides MDM MUX device using a beam propagation simulation.