Bicc Public Limited Company

Bicc Plc

Other

John E Taylor

Jonathan E Nevett

Ian W Keene

Stephen P Driskel

Malcolm D Barnett

Christopher J White

An optical fibre element for use in an optical cable comprises a flexbile elongate member having within and partially bounded by the elongate member throughout its length an elongate compartment; at least one optical fibre loosely housed in the elongate compartment; and means for retaining the optical fibre within the elongate compartment. The elongate member is resiliently set in such a form that the central longitudinal axis of the member follows a longitudinally extending path which, between any two longitudinally spaced positions, is greater in length than the rectilinear distance between the two positions. When the resiliently set elongate member is subjected to a longitudinally applied tensile force, the elongate member will tend to straighten in a lengthwise direction against the action of its resilient set, thereby to reduce the tensile force applied to the optical fibre. When the tensile force is removed, the elongate member will return under the action of its resilient set towards its original form. Two or more such optical fibre elements may be assembled together to form an assembly of optical fibre elements for use in an optical cable.

Optical cable

An elongate flexible core 1 especially suitable for use in an optical cable to be employed as an aerial cable has in its outer circumferential surface circumferentially spaced, longitudinally extending grooves 3 in which optical fibres 34 will be loosely housed and comprises extruded plastics material and a multiplicity of longitudinally stressed elongate flexible non-metallic reinforcing element each substantially encapsulated in the extruded plastics material, the multiplicity of non-metallic reinforcing elements being substantially evenly distributed throughout the cross-sectional area of the core. The non-metallic reinforcing elements preferably extend helically around the axis of the core a long length of lay and preferably constitute 60 to 70% by volume of the extruded plastics material. The non-metallic reinforcing elements are preferably made of an aromatic polyamide and the plastics material may be a thermoplastics material, a thermosetting material or a thermotropic liquid crystalline polymer. The core 1 may be a single elongate flexible body or it may comprise a plurality of elongate flexible bodies extending helically around the axis of the core.

Optical cable with nonmetallic reinforcing elements

An optical cable having a bore in which is loosely housed two helically extending optical fibre ribbons and which is filled with a greasy water-impermeable medium is manufactured by feeding four flexible cords of electrically insulating material into circumferentially spaced, longitudinally extending grooves in the outer surface of a stationary rigid tubular elongate guide of circular cross-section, helically lapping two optical fibre ribbons around the guide and the flexible cords so that the cords support the helically lapped ribbons, applying longitudinally to and transversely folding around the guide and the optical fibre ribbon a flexible strip of electrically insulating material to form a tube, introducing water-impermeable medium in a liquid or semi-liquid state through a bore in the guide and into the tube and extruding around the tube a sheath of electrically insulating material. Preferably, at a position downstream of the position at which water-impermeable medium is introduced into the tube, the flexible cords are fed through a die downstream of and in axial alignment with the guide so that the cords will lie along the center of the filled tube and will not inhibit movement of the helically lapped optical fibre ribbons when the cable is flexed or stretched.

Optical cable manufacture

An overhead electric conductor comprises a central tubular metal core, at least one layer of helically wound bare metal wires surrounding the core and, loosely housed in the bore of the core, at least one optical fibre element. The optical fibre element comprises a flexible tube of elongate transverse cross-section in which is loosely housed an optical fibre ribbon structure and which is resiliently set in such a form that it follows a path of smoothly curved undulations, the axes of curvature of which lie parallel to one another and normal to the axis of the tube. Should a tensile force applied to the overhead conductor be transferred to the loosely housed optical fibre element, the flexible tube of the element will tend to straighten in a lengthwise direction against the action of its resilient set thereby to reduce any tensile force that might otherwise be applied to the optical fibres and, when the tensile force is removed, the tube will return under the action of its resilient set towards its original form.

Overhead flexible electric conductor

In an optical fibre element comprising a flexible tube in which optical fibres are loosely housed, the tube is resiliently set in such a form that it follows a longitudinally extending path which, between any two longitudinally spaced positions, is greater in length than the rectilinear distance between the two positions. Preferably, the tube is resiliently set to follow a path of smoothly curved undulations, the axes of curvature of which lie parallel to one another and normal to the axis of the tube. When the resiliently set tube is subjected to a longitudinally applied tensile force, the tube will tend to straighten against the action of its resilient set, thereby to reduce the tensile force applied to the optical fibres.

Optical fibre element housed in a tube resiliently set in a form such

An electric conductor suitable for use in an overhead electrical and optical transmission system comprises a layer or layers of helically wound wires, at least one elongate compartment within and extending throughout the length of the conductor and, loosely housed in the elongate compartment, at least one optical fibre ribbon structure comprising a plurality of optical fibres and flexible elongate reinforcing elements of resilient material arranged side by side and embedded in an elongate body of plastics material, each resilient reinforcing element being set in such a form that the ribbon structure follows a path of smoothly curved undulations whose axes of curvature lie parallel to one another and normal to the longitudinal axis of the ribbon structure. If, when the conductor is installed or in service, the undulating ribbon structure is subjected to a tensile force, the ribbon structure will straighten in a lengthwise direction against the action of the undulating resilient reinforcing elements thereby reducing the tensile force otherwise applied to the optical fibres and, when the tensile force is removed, the ribbon structure will return towards its original undulating form.

An optical fibre ribbon structure suitable for use in an optical cable or other application where there is a risk that optical fibres will be subjected to a tensile force comprises a plurality of optical fibres and flexible reinforcing elements of resilient material arranged side by side and embedded in an elongate plastics body. Each resilient reinforcing element is set in such a form that the ribbon structure follows a path of smoothly curved undulations whose axes of curvature lie parallel to one another and normal to the longitudinal axis of the ribbon structure. When the undulting ribbon stucture is subjected to a tensile force, the ribbon structure straightens in a lengthwise direction against the action of the resilient reinforcing elements thereby reducing the tensile force otherwise applied to the optical fibres. When the tensile force is removed, the ribbon structure returns towards its original undulating form.

Optical fibre ribbon structure

An erosion-preventing structure for use in strengthening a river bank or in desert reclamation is formed from a stack of toroidal objects such as used vehicle tires. The toroidal objects are disposed in a plurality of relatively offset layers which are held against relative movement and adjacent tires in a layer are secured together.

Formation of barriers

In effecting a joint between two optical fibres an elongate gauge having a cross-sectional shape and size corresponding to that of each of the optical fibres to be jointed is laid on a substantially flat surface of a soft, substantially non-resilient metallic body, e.g. annealed copper, and is pressed into the surface to form in, and between two edges of, the surface a groove of a substantially complementary cross-sectional size. The gauge is removed and the two optical fibres are aligned in the groove so formed in such a way that neighboring ends of the optical fibres substantially abut. A second body having a flat surface is applied to the grooved surface in such a way that its flat surface is in interfacial contact with the grooved surface, and the two bodies are secured together.

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Maidenhead, United Kingdom

John E Taylor