Experimental study of Brillouin scattering in fluorine-doped single-mode optical fibers.

We experimentally investigate Brillouin scattering properties in fluorine-doped single-mode optical fibers. The effective acoustic velocities determined from the measured dependences of acoustic resonance frequencies on optical wavelength are approximately equal to the individual acoustic velocities in the core and/or cladding regions. Brillouin gain coefficients are experimentally characterized and compared with that in a standard GeO(2)-doped single-mode fiber. The result indicates that the acousto-optic coupling efficiencies in all fibers are almost 100%, which means that Brillouin threshold value can not be simply increased by fluorine doping. Moreover, it is found that the dependences of acoustic resonance frequencies on applied strain or temperature change are quantitatively enhanced by fluorine dopants, which is in opposite trend when compared with germanium ones.