Abstract: The eccentricity of an optical fiber core within a transparent fiber jacket is monitored by directing light towards the fiber and obtaining a returned light intensity profile as a function of the angle at which light is returned from the fiber. Any deviation from symmetry of the profile is an indication of eccentricity of the fiber core within the jacket. The method can be used for in-line monitoring when producing fiber with an extruded jacket. The technique is substantially simpler than known techniques which require the use of coherent light for generation of optical fringes.

Abstract: In a known optical cable, optical fibers are loosely laid in a number of grooves formed within an elongate plastics extrusion. Typically the grooves follow a helical path with periodically reversing pitch, the helices centered on a central longitudinal axis of the cable. A primary reason for the helical lay is to prevent the fibers from becoming stressed should a bend occur in the cable. A further benefit of loose laying of fibers in a helical groove of periodically reversing pitch is that any elongation of the cable core is not immediately transmitted to the fiber supported by it. The fiber will move from its initial loose laid position both in a direction towards the inside curve of the helix and in a direction towards the base of the grooves. When it bears against the cable core over an appreciable length, the fiber will then be subjected to tensile stress.

Abstract: Optical fiber wound onto a take-up reel after production is invariably tensioned such that results of characterization tests performed on the wound fiber are markedly different from such results obtained when the fiber is untensioned. Doubly winding the fiber to minimize tension is a laborious procedure. The invention covers a reel which has an adjustable hub circumference. Adjustment can be made with the fiber wound onto the hub so allowing rapid characterization of the fiber prior to restoring the fiber and the hub to their normal storage positions for fiber shipment.

Abstract: An optical switch having a light input side and a light output side where there are a plurality of optical waveguides with light collimating lenses on one of the sides with the lenses in spaced positions and, on the other side there is an optical waveguide with a light collimating lens. To enable light to be transferred between the latter waveguide and any of the other lenses, it is movable to bring its lens into any of a plurality of switch positions, each corresponding to the position of one of the other lenses, and means is provided to move the lens selectively between positions. In preferred arrangements, the plurality of lenses are arranged around at least one pitch circle but a linear arrangement of lenses is also possible. An electric stepping motor is ideally used for the switching operation.

Abstract: A narrow beam from a laser source-like light beam is projected on an object, the light scattered from the projected spot of the object is detected by light detecters at a plural number of the detecting positions. The distribution of the scattered light is detected by comparing the values of the densities of the scattered lights at the plural number of the detecting positions among each other in such a manner that it is determined from the distribution of the scattered light whether there is a defect on the projected spot or not.