Fig. 1. Optical interconnection between SOI waveguides based on PWB

Fig. 2. PWB interconnection between SOI waveguides and multicore fibers^［38］

Fig. 3. PWB design and test between InP lasers and silicon chips

Fig. 4. Eight-channel transmitter communication chip based on PWB^［37］

Fig. 5. Micro-space optical device with an integrated degree based on two-photon polymerization

Fig. 6. Combining of free micro-space optical device to achieve on-chip interconnects^［43］