Assembly requirements for multi-channel coupling micro-optics in board-level optical interconnects

The compatibility to standard surface mount technology (SMT) seems to be the answer for cost-effectiveness that ultimately hinders the competitiveness of board-level optical interconnect technologies compared to their conventional but still evolving electrical counterparts. These short-distance optical links will be most likely employed as parallel high bit-rate busses and hence require multi-channel coupling. A multi-fiber based TIR micro-optic has been presented before. This paper describes the in-depth experimental investigation of all relevant coupling interfaces for an entire optical on-board link. By means of spatial optical loss measurements the maximum allowable misalignments between link components (VCSEL, microoptical coupling elements, integrated waveguides and p-in-photodiode array) are determined. As a result the SMT compatibility with passive alignment could be proven. Following the optical simulations using the ZEMAX^® optical design tool are verified with these experimental results. A simplified model of the fiber based coupling element and a source model of the used VCSEL will be presented. The tolerance analysis from the optical modeling is in very good agreement with the experimental data. Additionally, the paper proposes a novel integrated micro-optic that allows for volume manufacturing. The above derived results can be used for designing and optimizing the novel micro-optics.