Forward Brillouin scattering in holey fibers

Forward Brillouin scattering behavior of a holey fiber (HF) is investigated experimentally. The shear and longitudinal acoustic velocities are evaluated from measurements of forward and backward Brillouin scattering, respectively. Experimentally obtained results reveal that the acoustic velocity ratio, given as alpha (=shear velocity V-S/longitudinal velocity V-L), decreases as the ratio of the total air-hole area to fiber cross-sectional area becomes large. This means that increasing the air-hole area in an HF's cross section lowers the shear velocity with respect to the mixed tortional-radial (TR2m) modes.