Opto-mechanical properties of fibres—5: Refractive index profile of stretched ‘terylene’ polyester fibres

Abstract

The changes of cross-sectional area and refractive-index profile of ‘Terylene’ polyester fibres after stretching have been studied. The cross-sectional shape is determined from the diffraction pattern of a HeNe laser beam. Multiple-beam Fizeau fringes in transmission are used to determine the refractive index profile of these fibres at different draw ratios. A microstrain device connected to a wedge interferometer is utilized for this purpose. Microinterferograms are given for illustration.