Abstract: A method of fault location in a glass fibre optical waveguide comprises using a laser device to provide pulses of light, feeding the light pulses into a glass fibre optical waveguide, feeding light pulses reflected from the fault in the glass fibre waveguide into the laser device in which their character is changed and determining the location of the fault from the known propagation time of the reflected pulses.The invention also includes an arrangement for carrying out this method.

Abstract: A matrix to be used for fabricating disc shaped record carriers is produced by illuminating a photolacquer layer with a laser beam while the layer moves transverse to the beam axis and by controlling the beam so that it simultaneously produces a succession of spots modulated according to the information recorded and a continuous strip narrower than the spots and serving to provide a track guide for the scanning element of a playback device with which such a record carrier is to be used.

Abstract: A pickup system for playing back signals stored on the surface of a carrier in a form providing an optically detectable property which varies as a function of the time pattern of the stored signals, the storage being constituted by undulations or variations in the reflectivity of the carrier surface and the pickup system employing a laser beam which is reflected in a manner controlled by the stored information. The system includes a laser radiation generating element forming part of an optical resonator which also includes the carrier surface so that the intensity of radiation oscillations in the resonator is influenced by the surface and varies as the carrier moves relative to the laser element. The system also includes an output member for converting such intensity variations into an electrical signal representative of the stored signals.