Design and demonstration of optical-PCB-based optical serial bus for high-speed computer interfaces

Abstract

This thesis proposes optical printed-circuit board (OPCB) based optical serial bus (OSB) for high-speed computer interfaces. The proposed OPCB embeds an waveguide component which is formed using silica fiber as a waveguide medium and seamlessly linking the 90°-bent parts to the planar optical layer. The component was designed through considerations of optical loss, mechanical and thermal stability, module packaging, and applicability in PCB system in determination of fiber-core-diameter, bending radius, waveguide-mounting material and packaging structure. The insertion loss for the whole waveguide component was as low as -0.145 dB and not significantly degraded by thermal stress similar to the PCB lamination process. In the packaging of optical transmitter (Tx) and receiver (Rx) modules, we used a ceramic lid on which optical devices and IC chips were integrated and guide holes were formed. The optical Tx/Rx modules assembled on the waveguide plate showed a successful data transmission up to 8 Gb/s. An OSB system was designed and demonstrated using USB bus signals. The OSB system is composed of optical modules, direction circuits for isolating bidirectional signal and level shifters for interface matching between direction circuit and optical modules. The direction circuits showed successful control and isolation between downstream and upstream of bidirectional signals. Moreover, optical link tests between optical modules identified data transmission with the OSB signal, and showed clear eye-diagram in spite of -38.3 dB of attenuation. The results demonstrate that this investigation could be applied for high-speed computer interfaces based on an OPCB.