METHOD OF AND APPARATUS FOR FLEXIBLE TWISTED BODY

An overhead electric conductor with optical fibres 3 loosely housed in the bore of a central core 1, which bore also contains a greasy water-impermeable medium 4, is manufactured by causing a preformed elongate metal member 2 of U-shaped transverse cross-section and the optical fibres to advance in the direction of their lengths, the rate of advance of the fibres being restrained. As the U-shaped elongate member 2 is transversely folded around the optical fibres 3, greasy water-impermeable medium 4 is injected into the bore of the elongate metal member 2 under a controlled pressure. The consistency of the greasy water-impermeable medium 4, the pressure and rate at which it is injected into the bore and the degree of restraint imparted to the optical fibres 3 is such that, in a predetermined length of the conductor, the length of the optical fibres exceeds the length of the bore by a controlled extent, preferably 1 to 30%.