title: Superluminal propagation at negative group velocity in optical fibers based on Brillouin lasing oscillation.
abstract: 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  ns/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.
authors.affiliation: Department of Physics, Key Laboratory for Laser Plasmas (Ministry of Education), Shanghai Jiao Tong University, Shanghai, 200240, China.
authors.forename: Liang
authors.initials: L
authors.lastname: Zhang
authors.forename: Li
authors.initials: L
authors.lastname: Zhan
authors.forename: Kai
authors.initials: K
authors.lastname: Qian
authors.forename: Jinmei
authors.initials: J
authors.lastname: Liu
authors.forename: Qishun
authors.initials: Q
authors.lastname: Shen
authors.forename: Xiao
authors.initials: X
authors.lastname: Hu
authors.forename: Shouyu
authors.initials: S
authors.lastname: Luo