Elastic waves in rods and optical fibers

Abstract This paper is a review of elastic waves in rods. This mature subject has important new consequences in optical fibers. The modulation or scattering of light by acoustic waves in optical fibers can be either harmful, as in catastrophic stimulated backward Brillouin scattering, or it can be put to practical use. While much of the paper is a tutorial description of basic knowledge about rod vibrations, several experiments are described that involve the interaction of light with vibrations in optical fibers. These include light modulation by thermally excited rod modes in an optical fiber, Brillouin gain measurements in fibers that are both acoustically and optically guiding, and some optical communication applications of stimulated Brillouin scattering. Reference is also made to other uses of acousto-optics in fibers.