Abstract: A crush-resistant tube for a plastics packaged optical fibre (1, 2) is formed by helically stranding together five or more non-circular cross-section wires (3) which are created from circular cross-section wires during the stranding operation.

Abstract: A design of plastics packaged glass optical fibre in which the plastics packaging consists of a urethane acrylate primary coating, a silicone rubber secondary coating and a nylon tertiary coating, the three coatings coacting to provide a pair of substantially decoupled mechanical filters.

Abstract: A single mode optical fiber having a central core region of uniform composition and thickness and core end regions each having a core with a graded composition and increasing thickness towards the ends of the fiber. The fiber maintains a constant normalized frequency with a minimum bending loss. Methods are also provided for forming the fibers from a fiber optic preform.

Abstract: An optical fiber connector in which each fiber is terminated by a coupling element comprising a cylindrical transparent body having a concave reflector on one end facing into the body and a circular reflector on the opposite end facing the concave reflector. The circular reflector has a diameter less than that of the cylindrical body and is concentric therewith. This arrangement has the advantage that the main focussing elements are reflectors and therefore require far less curvature than lenses.

Abstract: A strain sensor providing an optical read-out that is suitable for use in electrically noisy environment or one subject to mechanical vibration consists of one or a set of single mode optical fibres wound round an expanding strain member. The principle of operation relies upon the fact that transverse straining of a single mode fibre destroys mode degeneracy thereby producing birefringence effects that can be rendered obversable using polarized light and a polarization analyzer.

Abstract: An optical fiber cable comprising a close-packed assembly of cylindrical strength members defining at least one cuspid interstice loosely receiving a single optical fiber therein.

Abstract: A coupling arrangement for mating electrical or optical connector subassemblies in which opposing coupling members are secured by a bayonet arrangement about their outer perimeters. Resilient (spring) fingers on at least one coupling member engage bayonet key-ways about the opposite member outer surface. The key-way and finger interface at the locked position is along at least one chamfered surface to permit the resilient fingers to deflect radially outwardly and "ride out" of the locked position to allow connector separation in response to excessive cable tension.

Abstract: A single mode optical fiber having a central core region of uniform composition and thickness and core end regions each having a core with a graded composition and increasing thickness. The fiber towards the ends of the fiber maintains a constant normalized frequency with a minimum bending loss. Methods are also provided for forming the fibers from a fiber optic preform.

Abstract: An optical power divider is disclosed for single mode optical fibers. The fibers to be coupled are inserted in converging bores in a lower refractive index glass block which is collapsed about the fibers and drawn down. In the drawn down region the fibers are reduced in cross-section so that an appreciable proportion of the optical energy will be guided by the fibers while propagating in the surrounding lower refractive index glass block.