Abstract: A waveguide cable comprises an axially extending polymer sleeve, or group of sleeves, the molecules in the sleeve(s) being longitudinally orientated. The or each sleeve contains one or more dielectric optical waveguides. A plurality of elongate filamentary strengthening members encased in polymer sleeves extend axially of the cable around the polymer sleeve or sleeves.

Abstract: A submarine communications cable comprising a plurality of optical fibres extending longitudinally, an electrically conductive tube surrounding the plurality of fibres with radial clearance, the electrically conductive tube allowing the transmission of electrical power between repeaters and being rigid so that when incorporated in the cable it resists hydrostatic pressure at the sea bed.

Abstract: Apparatus for winding tape around an elongate core comprises a frame structure which supports one or more reels of tape. The frame structure carries a bobbin which is rotatable with the frame structure about the core. Tape passes from the reel to the bobbin and extends between a pair of contacts before passing through a slit to the core. The contacts are normally open but if the tape touches one of these that contact closes and the speed of the motor, which drives the frame structure is adjusted to maintain the tape between the contacts. This arrangement ensures a substantially constant pitch of the tape around the core.

Abstract: A method of coating a fibre in which a sleeve of polymer is extruded, fibre is fed into the sleeve as it is formed, and the diameter of the sleeve is reduced by a drawing process to produce a sleeve of polymer which loosely envelops the fibre. We also provide a fibre having a tubular sleeve of polymer, the sleeve having its molecules orientated to lie longitudinally with respect to the axis of the fibre. The sleeve has relative strength in a longitudinal plane and relative weakness in a transverse plane.

Abstract: A method of coating a fibre in which a sleeve of polymer is extruded, fibre is fed into the sleeve as it is formed, and the diameter of the sleeve is reduced by a drawing process to produce a sleeve of polymer which loosely envelops the fibre. We also provide a fibre having a tubular sleeve of polymer, the sleeve having its molecules orientated to lie longitudinally with respect to the axis of the fibre. The sleeve has relative strength in a longitudinal plane and relative weakness in a transverse plane.

Abstract: A launcher for waves of selected mode in an optical dielectric waveguide having a core surrounded by cladding, in which the launcher includes a prism of refractive index greater than that of the waveguide and preferably greater than that of the core of the waveguide which is placed against the waveguide either before or alongside an outwardly tapering portion of the waveguide. Light from a laser is directed through the prism on to the waveguide to induce the waves in the waveguide. A matching fluid, which may set to a solid, improved the coupling of the prism to the waveguide. A detector of similar construction is also described, the tapering of the waveguide being inward.