Abstract: An optical fibre sensor 11 has two monomode cores 13,14 arranged in a common cladding 15 to allow cross-talk of optical signals between the cores as a function of strain, temperature and optical wavelength. Optical signals are generated by a generator 16 at two wavelengths, at one of which cross-talk between the cores 13,14 is temperature independent. The generated optical signals are injected into the element 11 via an optical fibre lead 18 having a single monomode core 19 which is connected to one of the cores 13 of the element 11 at one end thereof and after cross-talk between the cores, optical signals are extracted from the element, for example via the same lead 18, and processed to determine temperature and strain at the element.

Abstract: A round birefraction dielectric wave-guide has in section a central round zone with a constant, or substantially constant, refractive index n1, an outer zone preferably with a constant refractive index n2 and an intermediate zone divided into 8 (or multiples of 8) angular sectors. Respective alternate sectors have refractive indices n3 and n4. Refractive index n3 may be constant but index n4 varies in inverse proportion to the square of the distance from the axis of the waveguide. N1 is greater than n2, n1 is greater tha n3 and n4 lies between n1 and n2. The wave-guide is subjected to torsion around the longitudinal axis of symmetry thereof and/or is spirally wound around a cylinder.

Abstract: An electrical termination comprises a cable lug 1 fitted to an end of an electric cable 3 and connected to a terminal 5 provided with an insulating bushing 6. An insulating shroud 13 comprising a rigid sleeve 14 and a removable closure element 15 fits over the terminal in spaced relationship thereto, with the space between the sleeve 14 and the bushing 6 at the end portion 19 of the sleeve 14 opposite the closure element 15 being closed by an annular insulating member 18. The sleeve and the closure element are provided with cooperating open end slots 20, 21 which define an aperture in the shroud in which a further insulating sleeve 23 fits so as to extend outwardly from the shroud. The cable lug 1 passes through the sleeve 23.

Abstract: A cable length of the type comprising a conductor, polymeric insulation 3 over the conductor, a semiconducting screen 4 over the polymeric insulation, a fault carrying screen 5 over the semiconducting screen, and a protective sheath 6 over the semiconducting screen has at least the leading end thereof partially prepared for jointing prior to laying of the cable. At the leading and or each end the cable is stripped back over successive increasing lengths 7, 8, 9 to its polymeric insulation 3, its semiconducting screen 4 and its fault carrying screen 5. A semiconducting sleeve 13 fits over the protective sheath 6, extends over the stripped lengths of fault carrying screen 5 and semiconducting screen 4 and abuts the end portion of the latter. A clamp 12 disposed within the sleeve 13 terminates the fault carrying screen 5 and a sleeve 19 of polymeric insulation is provided on the stripped length of polymeric insulation 3.

Abstract: A tubular sleeve 12 is applied over an elongate body 10 which has a diameter greater than the inner diameter of the sleeve. An end portion 12a of the sleeve is engaged over an end portion of the body 10 to form a partial fluid-tight seal therewith. The opposite end portion of the sleeve is temporarily closed and fluid under pressure is introduced to the interior of the sleeve to inflate it sufficiently to enable it to be floated along the elongate body. Then the sleeve is displaced along the body. The fluid may be air introduced to the sleeve interior through a valve 14 which also temporarily closes the sleeve end.

Abstract: In curing an extruded insulation layer of an electric cable by passing the cable through a catenary curing tube, a cable restraining device 8 is disposed at or just prior to the exit end of the catenary tube 11 and serves to apply to the cable 10 a restraint to oppose forces (developed by the hydrostatic pressure of the curing fluid) which tend to extrude the cable through the exit end of the curing tube. In the example shown, the device 8 comprises a set of resiliently flexible cones 9 and a clamping arrangement 12, 13 which is adjustable to adjust the degree of restraints.