Transition, radiation and propagation loss in polymer multimode waveguide bends

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Abstract
Design curves for insertion loss of multimode polymer waveguide 90° bends are reported as a function of bend radius for several waveguide widths. For the first time, to our knowledge, in multimode rectangular waveguides the insertion loss is resolved into its components of transition, radiation and propagation loss, in order of decreasing strength, separating them from input and output coupling loss by calibration and comparison of experimentally measured and beam propagation method (BPM) modeled curves. We used the method of nested bends for the first time in multimode polymer waveguides to calculate the propagation loss on a small substrate without using destructive cut-back. The lowest loss of 0.74 dB occurred for a 50 μm square cross section, Δn=0.0296, 13.5 mm radius waveguide bend.