  In this letter we experimentally demonstrate that the signal velocity,
defined as the earliest time when a signal is detected above the realistic
noise floor, may be altered by a region of anomalous dispersion. We encode
information in the spatial degree of freedom of an optical pulse so that the
imprinted information is not limited by the frequency bandwidth of the region
of anomalous dispersion. We then show that the combination of superluminal
pulse propagation and realistic detectors with non-ideal quantum efficiency
leads to a speed-up of the earliest experimentally obtainable arrival time of
the transmitted signal even with the overall pulse experiencing unity gain.
This speed-up is reliant upon non-ideal detectors and losses, as perfect
detection efficiency would result in the speed of information being equal to
the speed of light in vacuum, regardless of the group velocity of the optical
pulses.
