Measurement technique of OH-ion distribution profile in rod preform of silica-based optical fiber waveguides

To study the OH-ion contamination mechanism in silica-based optical fiber waveguides, a method for measuring the OH-ion distribution profile in fiber-rod preforms has been developed. Using a low-OH-content optical fiber as a light probe of the measuring set, high spatial resolution of several tens of micrometers was obtained. Using this technique, the OH-ion distribution profiles in nondoped silica-rod preforms were measured optically at 2.73 microm. The OH-ion distribution profile observed closely agreed with the calculated diffusion profile, from which the diffusion coefficient of OH-ion in silica glass was estimated to be ~7.0 x 10(-9) cm(2) sec(-1) at 1600 degrees C.