Simple technique to achieve fast light in gain regime using Brillouin scattering

We describe a novel technique based on stimulated Brillouin scattering for propagating fast light (signal advancement) with low distortion in optical fibers. The essence of the technique relies on the presence of two separate gain resonances in the Brillouin gain spectrum generated by cascading two different fiber segments showing distinct Brillouin shifts. It can be shown that in between these two gain spectra, a reduced group index can be obtained. To further optimize our results, we broadened the pump spectrum by introducing a modulation of the current driving the pump laser to achieve a delay-bandwidth product close to the optimum conditions. This scheme eliminates the need of an external optical modulator and offers the advantage of a much reduced signal distortion.