Fig. 1. Diagrams of stress distribution on neutral plane and flexible polymer waveguide with sandwich-like structure. (a) Diagram of flexible polymer waveguide with sandwich-like structure; (b) diagram of stress distribution on neutral plane

Fig. 2. Illustration of fabrication process of flexible waveguides

Fig. 3. Results of morphology characterization. (a) Three dimensional shape of waveguide obtained by laser confocal microscope; (b) cross-section micrographs of polymer waveguide observed by optical microscope; (c) typical top view of waveguides (SEM image)

Fig. 4. Transmission characteristics of flexible waveguide. (a) Diagram of waveguide coupling test system; (b) insertion loss of 10.5 cm waveguide channel; (c) measured propagation loss of waveguide using truncation method; (d) test results of waveguide channel crosstalk

Fig. 5. Relationship among bending loss, bending radius, and channel number. (a) Relationship between bending loss and bending radius; (b) insertion loss of waveguide after 1000 times bending with bending radii of 1 mm and 3 mm

Fig. 6. Experimental results of waveguide reliability. (a) TG and (b) DTG curves of polymer waveguide materials at heating rate of 10 ℃·min^-1 under N₂; (c) temperature-time curve of reflow soldering; (d) propagation loss of waveguides obtained by environmental reliability test