Imaging Assisted Dual Sided Light Coupling Technique for Propagation Loss Estimation of Waveguide Interconnects

A simple, fast, and robust technique for estimating waveguide loss is presented using the scattered light imaging from swapped input-output ports at different wavelengths. The propagation loss is determined by normalizing waveguide output-to-input intensity ratios, making the method insensitive to optical fiber-to-waveguide coupling efficiency. And the spatial variation effects along the waveguide length are mitigated by focusing on relative loss values. The approach is demonstrated on SU8 based multimode waveguides, including both straight and S-bend configurations with 5 mm radius of curvature and bend angles of 15°, 18°, 20° and 25°. The measured losses for these waveguides are (-17,-18,-20,-21,-25 dB/cm at 450 nm,(-19,-22,-24,-27,-33 dB/cm) at 526 nm, and (-9,-11,-14,-14,-24 dB /cm) at 635 nm respectively.