  Optical interconnects play a key role in the implementation of high-speed
short-reach communication links within high-performance electronic systems.
Multimode polymer waveguides in particular are strong candidates for use in
passive optical backplanes as they can be cost-effectively integrated onto
standard PCBs. Various optical backplanes using this technology and featuring a
large number of multimode polymer waveguide components have been recently
demonstrated. The optimisation of the loss performance of these complex
waveguide layouts becomes particularly important at high data rates (>=25 Gb/s)
due to the associated stringent power budget requirements. Moreover, launch
conditions have to be carefully considered in such systems due to the
highly-multimoded nature of this waveguide technology. In this paper therefore,
we present thorough loss and bandwidth studies on siloxane-based multimode
waveguides and waveguide components (i.e. bends and crossings) that enable the
implementation of passive optical backplanes. The performance of these
components is experimentally investigated under different launch conditions for
different waveguide profiles that can be readily achieved through fabrication.
Useful design rules on the use of waveguide bends and crossings are derived for
each waveguide type. It is shown that the choice of waveguide parameters
depends on the particular waveguide layout, assumed launch conditions and
desired link bandwidth. As an application of these studies, the obtained
results are employed to optimise the loss performance of a 10-card shuffle
router and enable >=40 Gb/s data transmission.
