Optomechanical design and characterization of a printed-circuit-board-based free-space optical interconnect package

We present a proof of concept and a feasibility demonstration of a practical packaging approach in which free-space optical interconnects (FSOI’s) can be integrated simply on electronic multichip modules (MCM’s) for intra-MCM–board interconnects. Our system-level packaging architecture is based on a modified folded 4f imaging system that has been implemented with only off-the-shelf optics, conventional electronic packaging, and passive-assembly techniques to yield a potentially low-cost and manufacturable packaging solution. The prototypical system as built supports 48 independent FSOI channels with 8 separate laser and detector chips, for which each chip consists of a one-dimensional array of 12 devices. All the chips are assembled on a single substrate that consists of a printed circuit board or a ceramic MCM. Optical link channel efficiencies of greater than 90% and interchannel cross talk of less than 220 dB at low frequency have been measured. The system is compact at only 10 in.3 (25.4 cm3) and is scalable, as it can easily accommodate additional chips as well as two-dimensional optoelectronic device arrays for increased interconnection density.