  We analyze fast and slow light transmission in a zig-zag microring resonator
chain. This novel device permits the operation in both regimes. In the
superluminal case, a new ubiquitous light transmission effect is found whereby
the input optical pulse is reproduced in an almost simultaneous manner at the
various system outputs. When the input carrier is tuned to a different
frequency, the system permits to slow down the propagating optical signal.
Between these two extreme cases, the relative delay can be tuned within a broad
range.

Optics