Abstract: An optical fiber cable having a tube in which is inserted at least one optical fiber and a mixture of a water-mediated expanding powder and a material with a particle size less than that of the water-mediated expanding powder is inserted in the tube. The percentage of the powder in the mixture is in an amount such as to block the flow of water to within a distance of less than about three meters from the point of ingress of the water in twenty-four hours and such as to bring about an increase in attenuation in the optical fiber, after it has been housed in the cavity, of less than 0.02 dB/km.

Abstract: In a method of manufacturing an optical fiber cable comprising optical fiber units 12 disposed within an extruded sheath 14 with water absorbent powder 16 being provided between the optical fiber unit or units and the sheath, the fiber units pass through an extruder cross-head 36 extruding said sheath 14 together with a tape 22 transporting the water absorbent powder 16. The tape is formed upstream of said extruder crosshead 36 into a channel into which said water absorbent powder is delivered and the tape is adhered to the inside surface 24 of said sheath 14 by fusion thereto.

Abstract: An optical fibre, comprising a glass core 10 surrounded by a glass cladding (11) of lower refractive index, is provided with inner and outer relatively high modulus plastics layers (12 and 14) spaced apart by a relatively low modulus layer 13. The low modulus layer is applied from an aqueous dispersion, and is dried but not sintered. This leaves the layer (13) in a form in which it has little adherence to the underlying inner plastics layer (12), thereby enabling the outer layer (14) to be readily peeled by mechanical means.

Abstract: Method and apparatus for manufacturing a cable having a channel for receiving energy conductors, e.g. optical fibers, with a channel cover which has a weak bond with the material forming the channel to facilitate removal of the cover. The plastic material which provides the channel and the plastic material which forms the cover are simultaneously extruded around optical fibers in two flows which are separated in advance of enclosing the fibers and which join with a weak bond as the flows meet thereafter. In the apparatus, the extruder has a tubular element through which the fibers are fed and the tubular element divides the plastic material into two separate flows in advance of a die. The tubular member is adjustable in position with respect to the die to balance or equalize the plastics flow.

Abstract: An optical fibre, comprising a glass core 10 surrounded by a glass cladding (11) of lower refractive index, is provided with inner and outer relatively high modulus plastics layers (12 and 14) spaced apart by a relatively low modulus layer 13. The low modulus layer is applied from an aqueous dispersion, and is dried but not sintered. This leaves the layer (13) in a form in which it has little adherence to the underlying inner plastics layer (12), thereby enabling the outer layer (14) to be readily peeled by mechanical means.