It is widely believed that the velocity of information ${\ensuremath{\upsilon}}_{i}$ encoded on an optical pulse is equal to the group velocity ${\ensuremath{\upsilon}}_{g}$, at least when ${\ensuremath{\upsilon}}_{g}$ is less than the speed of light in vacuum
c. On the other hand, several authors suggest that ${\ensuremath{\upsilon}}_{i}=c$, although the size of the signal traveling at this velocity may be small, thereby making it difficult to measure. Here, we measure ${\ensuremath{\upsilon}}_{i}$ for pulses propagating through a resonant ``slow-light'' medium where ${\ensuremath{\upsilon}}_{g}\ensuremath{\approx}0.006c$. We find ${\ensuremath{\upsilon}}_{i}=1.03{c}_{\ensuremath{-}0.25c}^{+0.49c}$, or that ${\ensuremath{\upsilon}}_{i}\ensuremath{\approx}168{\ensuremath{\upsilon}}_{g}$, clearly demonstrating that the speed of information cannot be generally described by ${\ensuremath{\upsilon}}_{g}$, but is characterized by its own velocity.
Dispersion properties of an optical medium can be greatly changed using electromagnetically induced transparency (EIT) and other nonlinear effects. Thus, the group velocity of light pulse can be much smaller (greater or even negative) than light speed in vacuum, which is called slow (fast) light. Slow and fast light are very useful in optical processing, such as optical buffer, switching, and storage devices. Usually, slow and fast light cannot be generated simultaneously in the same medium. In this paper, we propose applicable level structures to generate controllable slow and fast light simultaneously at two frequencies, with the same polarization.