Reduction of light-scattering loss in silica glass by the structural relaxation of “frozen-in” density fluctuations

Temperature dependences of light-scattering intensity in silica glasses were measured over a wide temperature range from 300 to 1 900 K. It was found that in OH-free silica glass, the diffusive density fluctuations are completely “frozen-in” at the glass transition temperature, while in OH-containing glass, OH gives rise to the structural relaxation of these “frozen-in” density fluctuations over 400 K below the glass transition temperature. This structural relaxation, expected to be caused by the introduction of some dopants with the same role of OH, can be used for reduction of the light-scattering loss in silica fibers.