Fig. 1. Schematic of light ray transmission in a curved waveguide

Fig. 2. Change in local numerical aperture with x under different bending radii R

Fig. 3. Schematic of radiation loss and mode conversion loss for S-shaped waveguide

Fig. 4. Variation in radiation loss with the ratio z/ρ in S-shaped waveguide

Fig. 5. Schematics of fabricated waveguides. (a) Reference straight waveguide; (b) S-shaped waveguide with different bending radii

Fig. 6. Fabrication process of waveguide. (a) Fabrication of under cladding layer; (b) fabrication of waveguide core layer; (c) fabrication of upper cladding layer

Fig. 7. Typical waveguide morphologies. (a) SEM images of waveguide morphology; (b) cross-section micrographs of polymer waveguides observed by optical microscope; (c1) typical overhead view of three-dimensional morphology and (c2) typical sidewall of three-dimensional morphology of waveguide obtained by laser confocal microscope

Fig. 8. Schematic of waveguide insertion loss performance test

Fig. 9. Measurement results of insertion loss. (a) Insertion loss of all 60 channels in straight waveguide; (b) insertion loss of bending waveguide with different transition arcs

Fig. 10. Distribution of losses in fabricated S-shaped bending waveguides among the possible attenuation causes