Characterization of optical fiber preforms by line-focus-beam acoustic microscopy

摘要

An ultrasonic method of line-focus-beam acoustic microscopy is applied to an analysis of the mechanical properties of silica-based optical fiber preforms. A first-deposition-stage optical fiber preform with GeO/sub 2/ and F dopants and 80-mm outer diameter, fabricated by the vapor phase axial deposition (VAD) method, is used in the experiments. The leaky surface acoustic wave (LSAW) velocity profile along the radial direction is measured at 225 MHz and compared with that calculated from the chemical composition obtained by electron probe microanalysis. It is found that the LSAW velocity profile corresponds mainly to the dopant distribution, and the difference between the measured and calculated velocity distributions suggests that a residual stress distribution in the preform is detected in the measured profile.