Rayleigh scattering-assisted narrow linewidth Brillouin lasing in cascaded fiber

We report a single frequency lasing phenomenon with a narrow linewidth of ~3 kHz in cascaded fiber that is composed of three types of low-loss communication fibers. The Rayleigh scattering of the Brillouin Stokes light created in the middle fiber section along both directions is enhanced by the other two fiber sections. When the Brillouin gain of the middle fiber exceeds the effective loss of the Brillouin stokes light in a roundtrip, a narrow linewidth lasing is observed on the top of the Brillouin spectrum line of the middle fiber. To the best of our knowledge, it is the first report on Rayleigh scattering-assisted Brillouin lasing with single frequency and narrow linewidth in cascaded low-loss communication fibers.