Abstract: An underwater optical fiber cable for laying at great depths in which an optical fiber core containing a plurality of optical fibers is protected by a peripherally segmented metal tube, each metal segment, in cross-section, having the shape of a sector of an annular, which is surrounded by at least one layer of elongated metal elements wound helicoidally around the tube, each element having radially extending sides which have radial lengths less than the peripheral lengths of the peripheral surfaces of the element. The layer or layers are surrounded by a watertight, conductive metal sheath and preferably, the sheath is surrounded by a plastic sheath.

Abstract: Telecommunication elements each comprising one or more optical fibers surrounded by one or more layers of a plastic are wrapped with a non-metallic protective layer. The protective layer is enclosed by a metal tube which has at least portions which press into the protective layer so as to provide dimensional stability to the elements and protective layer within the tube. The metal tube may have a cylindrical inner wall or be a corrugated tube, and such tube protects the optical fibers with respect to electrical discharges.

Abstract: An optical fiber element comprising an optical fiber surrounded and protected from mechanical stresses by three layers of plastic material, the intermediate layer having a modulus of elasticity substantially less than the moduli of elasticity of the adjacent inner and outer layers and less than one Kilogram/mm.sup.2.

Abstract: A direct current, electric, submarine cable which may be used in long lengths and at great depths and which has improved voltage breakdown characteristics with respect to voids which form in the insulation. The cable has a conductor surrounded by an inner semi-conductive screen which is surrounded by cellulose paper tape insulation which is surrounded by an outer semi-conductive screen which is surrounded by a metal sheath. The paper tape is impregnated with a compound comprising a viscous hydrocarbon oil containing a substance having polar groups, the amount of the substance being sufficient to make the volume resistivity of the compound 100 times lower than the volume resistivity of the tape with the compound therein.

Abstract: The invention concerns an improvement in taped cables having large diameter and suitable for use at voltages up to and over 1000 kV. The taping of one or more layers is wound according to a double-start or multi-start helix, said helix having an inclination less than 75.degree..

Abstract: A submarine cable and an electric power line using such cable for transmitting electric power at high voltge from a first point adjacent the surface of a water body to a second point adjacent the surface of a water body, a portion of the cable lying in great water depths where the hydrostatic pressure is high. The cable comprises at least three sections, each section having its insulation dimensioned or selected for operation at the high voltage when subjected to the ambient pressures. The section, or sections, lying at great depths has insulation with a voltage breakdown strength which varies with pressure, the strength increasing with pressure, so that the insulation thereof may be less than would be required if the such sections were to be used under pressures less than those at the great depths.