Optical Fiber Sensors Based on Brillouin Scattering

When Leon Brillouin wrote his thesis in 1920 about how thermal agitation affects light and X-ray scattering by a transparent homogeneous body, he never would have imagined that his discovery would still generate scientists’ passionate interest in the 21^st century. In his research, Brillouin concluded that density fluctuations in a medium result in thermally generated sound waves, and that such thermal agitation is capable of scattering incident lightwaves with shifted frequency. The presence of an acoustic wave in the medium contributes to the generation of two new spectral components—the Stokes and anti-Stokes waves with down- and up-shifted frequencies.