APPARATUS FOR DETERMINING THE REFRACTIVE INDEX PROFILE OF OPTICAL FIBRES AND OPTICAL FIBRE PREFORMS

摘要

The apparatus comprises an opaque screen, which is placed between a light source and a fibre or preform whose refractive index profile is to be determined. The screen has an oblique slit which forms a beam illuminating a plane section of the fibre or preform, and an optical system forms a nearfield image of the beam incident on the fibre or preform and a far-field image of the refracted beam, in two perpendicular directions on a photosensitive screen. The image formed on the screen is scanned by the scanning system of a television camera of which the photosensitive screen forms part, and the deflection function and hence the refractive index profile are obtained from the coordinates of the points of maximum brightness by using a computing system.