Passive Optical Components for Chip-on-Board Type Optical Interconnection

摘要

Passive optical components for optical interconnection using hybrid optical printed-circuit boards (PCBs) where electrical and optical layers are integrated into one board has been studied. We present detailed fabrication processes and optical characteristics of optical PCBs and connectors for optical coupling between vertical and horizontal directions. Two kinds of optical PCBs, polymer-waveguide-embedded and silica-fiber-embedded PCBs, were prepared. For the polymer-waveguide-embedded PCB, the polymer waveguide was formed lithographically on a FR-4 board and its core has 100 μm width and 60 μm thickness. The waveguide-defined board was covered with another FR4 plate and then laminated at 185℃ under the pressure of 35 kg/cm~2. After lamination the transmission loss of the waveguide was -0.53 dB/cm. For the fiber-embedded PCB, fibers with 100μm core diameter were inserted in grooves formed on a FR-4 board and they followed a similar lamination processes. The propagation loss of the fiber-embedded board at 850 nm was negligible in board scale. We also prepared 2 types of connectors for optical coupling between the surface mounted transmitter or receiver modules and the optical PCBs; 45°-ended fiber block and 90°-bent fiber connector. The insertion losses of the 2 kinds of connectors were, respectively, -0.15 dB and -0.25 dB. The best combination between the optical PCBs and connectors in view of optical characteristics and packaging is fiber-embedded board and 90°-bent fiber connector. They show successfully optical link of 2.5 Gbps with a very low coupling losses of -4.4 dB and a low optical crosstalk of-53 dB.