The spectral dispersion curve and the refractive index profiles of polypropylene fibre are determined. Multiple-beam Fizeau fringes, a two-beam interference Pluta microscope, a manual variable wavelength system and the automatic variable wavelength interference technique (VAWI) are used to compare the results. A comparison of the optical properties measured using these four techniques is outlined. Also, the advantages, accuracy and limitations of these techniques are dealt with. Microinterferograms are illustrated.