Optical fibre cable

Claim 2

An optical fibre cable comprising a longitudinally extending crush resistant central core formed with a plurality of circumferentially spaced, longitudinally extending ribs which lie at an angle to the core axis, and define grooves between the ribs, a plurality of fibres extending along the grooves, and a protective sheath surrounding the core and fibres, the sheath comprising an inner metal layer and an outer water impermeable polymeric layer, the metal layer extending around the core and being carried upon outer ends of the ribs to dissipate crushing loads upon the metal layer directly down the ribs.

Claim 3

A cable according to claim 1 wherein the metal layer is formed with circumferentially extending corrugations.

Claim 4

A cable according to claim 1 wherein the metal layer has overlapped ends to form an axially extending overlap, the metal layer is coated on its outer surface with a polymeric material, said material being compatible with the polymeric layer, and the polymeric layer being an extruded layer and being heat bonded to the coating layer.

Claim 5

A cable according to claim 3 wherein both surfaces of the metal layer are coated with the polymeric material, and the two coatings are bonded together at the overlapped ends.

Claim 6

A cable according to claim 1 wherein the protective sheath further includes another metal layer surrounding said outer water impermeable layer, and a further water impermeable polymeric layer surrounds said other metal layer.

Claim 7

An optical cable comprising a longitudinally extending crush resistant central core formed with a plurality of circumferentially spaced ribs which extend longitudinally of the core and around the core at an angle of the axis of the core, the ribs being tapered outwardly towards their outer ends and defining grooves between the ribs, a plurality of fibres extending along the grooves, and a protective sheath surrounding the core and fibres, the sheath comprising an inner metal layer having corrugations lying at a different angle to the core axis from the angle of the ribs, overlapped ends to form an axially extending overlap, and a coating on its outer surface of a polymeric material, the sheath also comprising a layer outwardly of the metal layer of polymeric material compatible with and bonded to the polymeric material of the coating.

Claim 8

An optical cable comprising a longitudinally extending crush resistant central core formed with a plurality of circumferentially spaced ribs which extend longitudinally of the core and around the core at an angle of the axis of the core, the ribs being tapered outwardly towards their outer ends and defining grooves between the ribs, a plurality of fibres extending along the grooves, and a protective sheath surrounding the core and fibres, the sheath comprising an inner metal layer having corrugations lying at a different angle to the core axis from the angle of the ribs, overlapped ends to form an axially extending overlap, and a coating on its outer surface of a polymeric material, the sheath also comprising a layer outwardly of the metal layer of polymeric material compatible with and bonded to the polymeric material of the coating.