Observation of hole burning in spectrum of SBS in optical fibres under CW monochromatic laser excitation

The theoretical description of SBS is based on the assumption that the scattered radiation is homogeneously broadened (Lorentzian gain profile). On the other hand there are several observations that both the width and shape of the line may differ from this classical description. In particular, in silica optical fibers considerable broadening of the Brillouin scattering spectrum, compared to bulk silica, has been reported, attributed to imperfections in the fiber, though as yet the nature and form of the broadening has not been determined. In this work the authors report first direct experimental results that show the SBS spectrum in optical fibers to be inhomogeneous in nature