In short-range interconnect applications, one question arises frequently: When should optical solutions be chosen over
electrical wiring? The answer to this question of course depends on several factors like costs, performance, reliability,
availability of testing equipment and knowledge about optical technologies, and last but not least, it strongly depends on
the application itself. Networking in high performance computing (HPC) is one such example. With bit rates around 10
Gbit/s per channel and cable length above 2 m, the high attenuation of electrical cables leads to a clear preference of
optical or active optical cables (AOC) for most planned HPC systems. For AOCs, the electro-optical conversion is
realized inside the connector housing, while for purely optical cables, the conversion is done at the edge of the board.
Proceeding to 25 Gbit/s and higher, attenuation and loss of signal quality become critical. Therefore, either significantly
more effort has to be spent on the electrical side, or the package for conversion has to be integrated closer to the chip,
thus requiring new packaging technologies. The paper provides a state of the art overview of packaging concepts for
short range interconnects, it describes the main challenges of optical package integration and illustrates new concepts
and trends in this research area.