Abstract
Diffraction patterns of HeNe laser beam, Becke-line, two-beam and multiple-beam interference, have been applied to study the optical properties of cuprammonium fibres. The area enclosed under the fringe shift is considered to represent the optical path difference integrated across the fibre, and it has been used to determine the refractive indices of fibres for light vibrating parallel and perpendicular to the fibre axis, hence the birefringence.