Opto-mechanical properties of fibres—4: Optical anisotropy in ‘Terylene’ polyester fibres

The variation of refractive indices and birefringence of ‘Terylene’ polyester fibre with different draw ratios is studied dynamically by interferometry. The polarizing interference microscope is used with a fibre manipulation device. An empirical formula is deduced for the relation between the mean birefringence Δn and the draw ratio R of ‘Terylene’ polyester fibres which is useful in the adjustment of the drawing process. The effect of draw ratio on the refractive index profile is studied. Microinterferograms are given for illystration.