Abstract: An apparatus (12) is provided for use in determining a length at least representative of the length of a tube that defines a passage in an optical fibre cable (10) along which an optical fibre unit can be installed by blowing. The apparatus (12) comprises a pressure reservoir (32) in which a gas at a known pressure can be stored, outlet piping (34) connected with the pressure reservoir (32) and having an outlet end spaced from the reservoir for connection to a tube of the optical fibre cable (10). The apparatus has a pressure detecting arrangement (42) for detecting gas pressure in a tube connected with the outlet end of the outlet piping (34).

Abstract: An apparatus for installing an optical fibre cable in a duct. The apparatus has feed means engageable with the optical fibre cable for feeding the cable toward the duct, means for directing a gaseous flow into the duct for propelling the optical fibre cable along the duct and drying means disposed upstream of the feed means for removing moisture that may be present on an exterior surface of the duct.

Abstract: An apparatus for and method of installing a cable in ducting from a location intermediate the length of the ducting. The cable is provided in a coil at the location and some cable is passed from one end of the coil into a first portion of the ducting extending from the location to one end of the ducting. The remaining cable is passed from the other end of the coil into a second portion of the ducting extending from the location to the other end of the ducting.

Abstract: An optical fibre cable for blown installation has a tubular central strength member (114) about which tubes (112) loosely housing optical fibres (116) are stranded. The jacket (118) is preferably formed from a high density polyethylene material and is extruded over the core (100) on which rip cords (124) are positioned. Water blocking compound (126) is provided in each tube (112) in any spaces therein which would otherwise be void. Also a water blocking material (128) is provided between the sheath (121) and the layer defined by the helically wound wrapping tape (122) or binding yarn in any spaces between the tubes (112) which would otherwise be void.

Abstract: An aerial cable installation having an aerial cable suspended from a suspension point through a suspension device. This device has a clamp having two saddle members engaging the cable on diametrically opposite sides thereof and a plurality of nut and bolt assemblies extending through aligned holes in flanges of said saddle members for resiliently biasing the saddle members toward each other to clamp against the cable with a selected clamping force. To this end, each nut and bolt assembly includes a helical spring mounted on the bolt thereof between said flanges and the nut of the assembly and the springs are compressed a predetermined amout which is adjustable by tightening or loosening said assemblies.

Abstract: In a method of installing a cable in ducting from a location (60) intermediate the length of the ducting, the cable is provided in a coil (62) at the location and some cable (64) is passed from one end of the coil into a first portion of the ducting extending from the location to one end of the ducting and the remaining cable (66) is passed from the other end of the coil into a second portion of the ducting extending from the location to the other end of the ducting.

Abstract: An assembly for use adjacent an earthed suspension region 20 of an all-dielectric self-supporting cable 10 suspended in an electric field at the earthed suspension region from a tower or the like for limiting dry band arcing adjacent the earthed suspension region is disclosed. The assembly includes an electrically conductive device 21 clamped to the cable remote from the earthed suspension region 20 and structure defining a current path having an arc gap connected between the device 21 and the earthed region 20.

Abstract: A device 22 for use adjacent an earthed suspension region 20 of an all-dielectric self-supporting cable 10 suspended in an electric field at the region 20 from a tower or the like for limiting dry band arcing adjacent the region 20 is disclosed. The device includes members 34, 36 for defining a sleeve 26 for fitting to the cable adjacent this region 20 and elements 38, 40, 42, 44 for defining two closures 28, 30 for the sleeve. These closures are engageable with the cable at longitudinally spaced apart locations for forming with the cable and sleeve a closed zone 32 between the closures. Use of the device maintains the outer surface of the cable dry over a portion 24 thereof adjacent the region 20 which would otherwise be susceptible to dry band arcing.

Abstract: In order to install an optical fiber cable 110 in a duct 112 a plurality of vents 130, 132, 134 spaced apart along the duct are operated such that during blowing any vent 130 upstream of the leading end 138 of the cable is closed and when there is at least one vent 132, 134 downstream of the cable leading end at least the downstream vent 132 closest to the cable leading end is open for venting gas from the duct. In this way the pressure decay and pressure gradient profiles are modified during installation to improve installation performance.

Abstract: An assembly comprising a self supporting aerial cable and tension clamp means including gripping means for gripping the cable, the gripping means comprising at least one helically wound rod fitted over the cable's outer sheath, wherein ##EQU1## where C is the outer diameter of the cable, R is the diameter of the or each rod and W.sub.R is the outer diameter of the unstressed winding of the or each rod.

Abstract: The moisture content of compressed air being supplied by a compressor 24 to propel an optical fibre line 18 along a duct is monitored by a dew point meter 22 and adjusted such that it is maintained within a predetermined range. The adjustment is carried out by passing the compressed air through two passages 30, 32 arranged in parallel with one passage 30 being provided with means 20 for increasing the moisture content of the air passing therethrough and adjusting the relative flow rates through the two passages.

Abstract: An installation 10 comprising a line 12 extending between and suspended from a plurality of spaced apart aerial suspension locations 14 defines a passage for an optical fiber unit. The line comprises a plurality of elongate tensile resistant tubes 18 connected end-to-end by respective connectors 20. The line is secured to each suspension location by respective securing means 22 which are secured to said line at two spaced apart locations 28, 30 thereon such that the portion 26 of said line between these locations is untensioned and includes a connector 20. The securing means 22 is adapted to allow tensioning of the portion 26 of said line when the tensile load on the line adjacent thereto on either side of said suspension location reaches a first predetermined amount, and the connector 20 is adapted to cause the end-to-end connection of the tensile resistant tubes 18 connected thereby to break when the tensile load on said portion reaches a second predetermined amount.

Abstract: An optical fibre cable has a channel (2) loosely housing an optical ribbon element (3) and a non-optical ribbon element (3A) which both have an evenly distributed excess length of between 0.5% and 1% and adopt a regular undulating configuration in a thixotropic water blocking gel (28) in the channel.

Abstract: An all-dielectric optical fibre cable comprises a strength member rod having a roughened surface formed by a moulding process during manufacture of the rod using a woven tape imprint, which serves to improve adhesion between an extruded outer sheath and the surface of the rod. The cable is suitable as an all dielectric aerial cable for large unsupported spans eg 500M, alongside a high voltage electricity distribution system.

Abstract: An optical fiber cable package has a kingwire and a plurality of acrylate primary coated optical fibers all embedded in a one-shot extrusion of low melting point plastic, e.g. Hytrel 40. The fibers have a zero angle of lay. The package is particularly but not exclusively suitable for use in an optical fiber submarine cable.

Abstract: A design of optical fiber cable that is gas blocking has a set of four plastics packaged optical fibers (2) around a central strength member (1). The fibers and strength members are embedded in spaced apart relationship in a nylon 12 pressure extruded sheath (3) which has been annealed to provide a contraction in the region of 1/4%.

Abstract: A plastic fiber cable has a flame retardant sheath which contains between 10-40% by weight of an inert filler, preferably titanium dioxide, which provides the sheath with thixotropic non-drip properties so that as well as possessing non-flammability properties the sheath when molten will also not drip and thus will not expose more flammable materials, such as the strands, inside the sheath.