High bit-rate optical interconnects on printed wiring board. Micro-optics and hybrid integration: Dissertation

Optical interconnects are foreseen as a potential solution to improve the performance of data transmission on printed wiring boards (PWB). Optical interconnects carry data signals as modulation of optical intensity, for instance through an optical waveguide, thus replacing traditional electrical interconnects. The aim of the research work was to study and develop board-level optical interconnection technologies that would be suitable for volume manufacturing with typical electronics production processes, such as surface-mount assembly and board manufacturing. More precisely, the work focuses on the hybrid integration of multi-channel optoelectronics transmitters and receivers, which are equipped with micro-optical structures enabling coupling to board-embedded optical waveguides. The presented integration schemes are based on the use of low-temperature co fired ceramic (LTCC) circuit boards with high-precision alignment structures. Two experimental set-ups were designed and implemented to study the feasibility of the proposed integration schemes. The first set-up enabled evaluation of three different kinds of optical coupling schemes, which are based on microlenses, micro-ball lenses and butt-coupling respectively. The other demonstrator is a parallel optical interconnect integrated on a standard PWB. The optical coupling is based on microlens arrays and a micro-mirror, which, together with four polymer multimode waveguides on the PWB, form the interconnections between the surface-mounted 4-channel transmitter and receiver components. The optical performance of the demonstrated structures is studied by modelling and characterisation. With the proposed improvements, the presented technologies are suitable for implementation of high bit-rate interconnections between ceramic-packaged integrated circuits or multi-chip modules on PWB.