Societa Cavi Pirelli S.p.a.

Pirelli Cavi E Sistemi S.p.a.

Prysmian S.p.a.

Gianfranco Colombo

Pietro Anelli

The present invention relates to a cable, in particular an optical fiber cable, which is resistant to the radial permeation and to the longitudinal propagation of water. This cable contains a water-soluble polymer material which is a water-swellable and water-soluble material. In particular, this cable is characterized in that, following the ingress of water into this cable, the propagation of water is impeded on account of the combined effect of the swelling of the water-soluble material and the formation of an aqueous solution of said material which has a predetermined viscosity, so as to impede the passage of the residual water. Preferably, the water-soluble material is chosen from polyacrylamide, modified polyvinyl alcohol, vinyl alcohol/vinyl acetate copolymers, polyvinylpyrrolidone, and mixtures thereof, the material preferably being a vinyl alcohol/vinyl acetate copolymer. The material can advantageously be extruded to form tubular elements for containing optical fibers, for example, two-layer tubular elements in which the inner layer is made of water-soluble material and the outer layer is made of a conventional polymer such as PE, PP or PBT.

Water-resistant cable

Hydrogen absorbing mixtures for protecting optical fibers from damage by hydrogen and optical fiber telecommunication cables containing such a mixture or mixtures. The mixture includes at least one oxide selected from oxides of titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, cerium, tin, lead and wolfram, at least one catalyst selected from among the transition metals, the inorganic and organic compounds of the transition metals and the complexes of the said transition metals, both by themselves as well as supported by inert materials, and an anhydrous salt which, on chemically reacting with water, forms crystalline hydrated compounds which are stable at temperatures up to at least 90.degree. C. The anhydrous salt may be one or more of anhydrous calcium sulfate, anhydrous calcium chloride, anhydrous sodium sulfate and anhydrous copper sulfate. In a cable, the mixture is between the cable sheath and the optical fibers or is incorporated in the sheath if it is made of polymeric material. The mixture may be used alone or dispersed in a filler and may be coated on or incorporated in a component of the cable.

Hydrogen absorbing mixture for optical fiber cables and cables

Optical fibers of an optical fiber, telecommunication cable are protected with respect to hydrogen by including in the cable a mixture of molybdenum trioxide and a catalyst selected from the transition metals, the inorganic and organic compounds of the transition metals and the organometallic acids of the transition metals, such mixture being used by itself or being supported by inert materials. The mixture may surround the fiber or fibers, be applied as a coating on a component of the cable, be incorporated in a component of the cable or be included in a rod or tube adjacent to the fiber or fibers and within the cable sheath.

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Sesto San Giovanni, Italy

Gianfranco Colombo