(A) Study on optical interconnection components and systems for waveguide-laminated optical PCBs

Abstract

Optical components for waveguide-laminated optical printed-circuit boards (OPCBs) such as transmitter and receiver (Tx and Rx) modules, waveguides for OPCB, and connectors have been studied to reduce the optical losses and to in-crease the stability of the optical interconnection system. The optical link system between field programmable gate array (FPGA) microprocessors was demonstrated applying the studied components. An one-unit optical waveguide in which each fiber strand does not have cutting-off points until reaching board surface was designed for laminating into printed-circuit boards (PCBs) to fabricate OPCBs. The optical loss occurring in free-space interfaces was fundamentally eliminated by employing the one-unit optical wave-guide. This OPCB structure reduced the insertion loss to a quite low value, 0.42 dB, which is a much lower value, compared to the 4.7 dB loss of the wave-guiding system developed in the previous work of our Photonic Computer Systems (PCS) laboratory. After the thermal stability test for the verification of lamination process at 200℃ for 4 hours, the insertion loss of the one-unit optical waveguide was not changed within the measurement error range. The optical loss variations by misa-lignments to the lateral and longitudinal directions of the one-unit optical wave-guide were investigated, and it is expected to give useful information for optical link system design. Optical Tx and Rx modules were designed and characterized for the application to the optical link system between FPGA microprocessor ICs based on the one-unit optical waveguide-laminated OPCB systems. The PCB part of the module was fa-bricated with a dimension of 9.5 mm × 10.5 mm × 1 mm to have compact and her-mitic assembling on the OPCB system. Their signal lines were simulated to be well impedance matched. They were designed to have 0.5-mm-high sidewalls to protect the packaged components inside them. The optical link evaluation of the packaged Tx and Rx modules...