GB2256499A - Electical cable having two insulated conductors and optic fibre - Google Patents

Abstract

An electrical supply cable e.g. for a domestic supply, includes inner 11 and outer 13 stranded conductors for the line and neutral supplies respectively. The cable further accommodates optical fibre element(s) 18 for the supply of telecommunications and/or television facilities. The electrical conductors 11, 13 are separated by insulation. <IMAGE>

Description

IMPROVEMENTS IN CABLES This invention relates to cables, and in particular to cables containing both electrical and optical elements.

There is an increasing interest in the provision of services, e.g. telecommunications and television, to domestic users via fibre optic transmission medium. The introduction of this technology has however been restricted by the difficulty of obtaining wayleaves for the installation of the cables by which the services are to be provided. A further problem where services are to be provided to new properties is that a further group of contractors is required in addition to those providing the conventional installation. This adds to the cost of the installation.

The object of the invention is to minimise or to overcome these disadvantages.

According to the invention there is provided an electrical power supply cable including a line conductor, a neutral conductor disposed around the line conductor and insulated therefrom, and one or more fibre optic transmission elements incorporated within said cable.

The cable may be installed by the electrical utility who will already have any necessary wayleaves.

Embodiments of the invention will now be described with reference to the accompanying drawings in which: Fig 1 is a cross-sectional view of an electrical cable incorporating fibre optic transmission elements; and Figs. 2 and 3 show alternative cable constructions.

Referring to Fig. 1, the cable includes a stranded central "Line" conductor 11, e.g. of copper or aluminium, which conductor is sheathed with a first suitably colour-coded layer 12 of a plastics material. A stranded 'neutral' conductor 13 us laid up on the plastics sheath 12 and is in turn sheathed by a second colour-coded layer 14 of plastics material. The structure is encased in a protective plastics outer sheath 15.

The second plastics sheath 14 and the outer sheath 15 are provided each with longitudinal recesses or grooves 16, 17. These grooves are in register whereby to form tubes for accommodating optical file elements 18, these elements being a loose fit in the tubes so as to minimise axial strain on the fibre during cabling and/or installation operations.

In use, the line conductor 11 and the neutral conductor 13 are coupled respectively to one phase conductor and the neutral conductor of a three phase street or main cable. The optical file elements 18 are.

coupled to corresponding elements carried either within the street cable or within an optical cable laid adjacent the street cable.

At the user end of the cable, the line and neutral conductors 11 and 13 are coupled to the supply meter and the optical elements are coupled to an optical termination unit disposed adjacent the meter.

Figs 2 and 3 show alternative cable constructions in which the fibre optic elements 18a are carried within plastics tubes lla, 13a which occupy the place of a corresponding conductor strand. The fibre elements are exposed when the cables are prepared for jointing. In the constructions of Figs. 2 and 3 the outer plastics sheath 15 (Fig. 1) may be dispensed with.

It will be appreciated that the cable constructions described above are not limited to domestic supply applications but may also be employed e.g. in the cabling of an office building.

Claims (7)

CLAIMS:

1. An electrical power supply cable including a line conductor, a neutral conductor disposed around the line conductor and insulated therefrom, and one or more fibre optic transmission elements incorporated with said cable.

2. A cable as claimed in claim 1, having a plurality of said elements accommodated within tubes.

3. A cable as claimed in claim 2 wherein said conductors each comprise respective conductor strands stranded together, and said tubes each occupy the place of a strand.

4. A cable as claimed in claim 3, wherein a said tube is stranded together with the strands of the line conductor.

5. A cable as claimed in claim 3 or 4, wherein a said tube is stranded together with the strands of the neutral conductor.

6. A cable as claimed in claim 2, wherein said tubes are formed by longitudinal recesses in a plastics sheath around said neutral conductor in registration with longitudinal recesses in an outer plastics sheath around said plastics sheath.

7. An electrical power supply cable substantially as hereinbefore described with reference to Fig. 1, 2 or 3 of the accompanying drawings.