We report superluminal propagation in optical fibers using Brillouin lasing oscillation in a ring cavity. Negative group velocity propagation through a 10-m single mode fiber has been experimentally demonstrated. An advancement of 221.2 ns was observed before the input signal, which was achieved with a very high slope efficiency of $211.3\mathrm{ns}/\mathrm{dB}$. This indicates that this way is suitable for long-distance low-loss superluminal propagation via optical fibers. Correspondingly, the group velocity is $-0.151c$ and the group index is $-6.636$—the highest group velocity ever reported for optical fibers.

• Received 19 March 2011

DOI:https://doi.org/10.1103/PhysRevLett.107.093903