MANUFACTURE OF A CIRCUMFERENTIALLY RIGID FLEXIBLE TUBE FOR AN OPTICAL CABLE

摘要

A circumferentially rigid flexible tube for use in loosely housing at least one optical fibre in an optical cable - especially an aerial optical cable - is manufactured by forming a plurality of flexible elongate flexible bodies, each of which has a transverse cross-section approximating to a sector of an annulus and in each of which a multiplicity of non-metallic reinforcing elements are encapsulated in and evenly distributed throughout the cross-sectional area of an extruded body of electrically insulating plastics material; causing each flexible body as it emerges from the extrusion die to follow a helical path in such a way that the convex outer arcuate surface of the body is maintained outermost and so treating the body that the plastics material in which the reinforcing elements are encapsulated sets; laying up the helically advancing flexible bodies together to form a flexible tube of circular cross-section which is rotating about its longitudinal axis and feeding at least one flexible optical fibre into the bore of the tube as it is being formed; and taking up the flexible tube in such a way that any residual torsion in the tube is removed.