  The propagation of short lightpulses in waveguiding structures with optical
feedback, in our case optical microresonators, has been studied theoretically
and experimentally. It appears that, dependent on the measurement set-up,
ballistic transport or interference in the time domain of fs and ps laser
pulses can be observed. The experiments are analyzed in terms of characteristic
time scales of the source, the waveguide device and the detector arrangement
and are related to Heisenberg's uncertainty principle. Based on this analysis a
criterion is given for the upper bitrate for error free data transmission
through optical microresonators.
