Corning Incorporated

Jerry D Nease

Bruce Warren Reding

Jerald B Dotson

A method for measuring the diameter of a transparent filament is provided which is substantially insensitive to ellipticity of the filament. The method comprises using an interference technique to measure the filament diameter at two locations which are spaced apart by an amount such that a plot of diameter versus angle of rotation for an elliptical filament calculated at the first location is approximately 90.degree. out of phase from the same plot calculated at the second location. Due to the phase difference, the average of the two measurements is substantially insensitive to ellipticity. For measurement apparatus comprising one laser and two detectors and for optical waveguide fibers having a cladding composed of fused silica, the two locations can be about 123.degree. apart. In other embodiments, a method for characterizing the non-circularity of a filament is provided. Apparatus for practicing the foregoing methods is also disclosed.

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Wilmington, NC, United States of America

Jerry D Nease