Simultaneous observation of superluminal and slow light propagation in a nested fiber ring resonator

We observe both superluminal and slow light propagation simultaneously in a nested fiber ring resonator. The two outputs of the resonator exhibit different absorption characteristics that produce opposite dispersion performance. The transmission spectra of two outputs are demonstrated experimentally for a variety of coupler settings. In particular, the group delays of the resonator for various values of the coupling coefficients are demonstrated theoretically and experimentally. We also discuss potential applications of the resonator.