Abstract: A drawer for a fibre management cabinet has a number of splice cassettes mounted on it by means of hinges. Each cassette hold a single splice. Fibres leading into a splice cassette are fed through the hinges of that splice cassette.

Abstract: A splice tray for accommodating optical fibers comprises a body with a plurality of splice holders at fixed locations thereon, the body having fiber access points at which fiber can enter and leave the body. Fiber paths are provided on the body leading from the access points to and from each splice holder, and each holder is adapted to receive and hold a splice reinforcer within which a fiber splice is present. The length of fiber is accommodated on either side of the splice. An adapter is used with a clip-on power meter to take readings of the transmissivity of fibers stored on storage leaves mounted on the tray body.

Abstract: In order to allow an optical cable to be accessed by spur cables at various points along its length after it has been laid, connection housings are provided at intervals along its length. A loop of the main cable is passed into each housing so that at a later date there is an excess of cable to enable connections to be made to it. Each housing contains fittings such as manifolds and organizer trays where the optical fibers are spliced and includes several access ports which are covered over until it is required to connect a spur cable to the main cable.

Abstract: Apparatus for laying an optical fiber unit into one of a plurality of parallel helical or reversing helical grooves in the outer surface of a cable core conveys the core along a path. A downstream guide is freely rotatable about the core path and has an aperture for feeding the fiber unit into the groove and an inward projection for following one of the grooves to maintain registration of the downstream guide with the groove. An upstream guide is indpendently rotatable about the core path and adjacent the downstream guide, and guides the fiber from a fiber supply toward the downstream guide. A servo drive is responsive to the rotation of the downstream guide relative to the upstream guide to drive the upstream guide such as to reduce that relative angle.

Abstract: An optical fibre cable comprising a generally non-metallic central core encased in a rigid metallic tube, at least one layer of longitudinal strength members which, or the inner one of which, overlays and is in contact with the rigid metallic tube, and a sheath overlaying the strength member layer, the layer of strength members including, in a respective gap or gaps, at least one longitudinally-welded metallic tube within which is encased at least one optical fibre.

Abstract: A support assembly for non-metallic cable incorporating a metallic support fitting and a preformed metallic stress limiter, the latter including a generally mushroom-shaped hollow body having a tubular stem portion inserted between one end of the support fitting and the cable, and a generally part-toroidal head portion having an outer profile which is smoothly curving.

Abstract: A submarine cable having an optical fibre core includes, as a longitudinal strength member of the core, a thermotropic plastics tube (8) having a generally rectangular-section longitudinal central passage and encased in a protective sheath (4), and at least one optical fibre ribbon (6), whose width is slightly less than the width of the passage, housed loosely within the passage, the ribbon (6) thereby being constrained to undulate in two dimensions in a longitudinal plane normal to its major surfaces. Preferably the tube (8) has a thickness substantially smaller than its width, so that its outer surface is also generally rectangular in section.

Abstract: Method of splicing optical fibres having a glass core and at least one plastics cladding layer comprises: stripping the or each cladding layer from the fibre ends, fusion splicing the bare fibre ends, placing the splice region in an open channel of a flexible mould, the channel being of uniform section, filling the gap between the bare, splice region and the inner wall of the channel with a curable plastics material, closing the flexible mould so that the channel walls close together and assume an internal shape complementary to that of the cladding layer or layers whereby to expel the surplus plastics material, curing the plastics material remaining within the mould, and opening the mould.

Abstract: A coupler for at least two optical fibres in which at least one port is redundant, e.g. a 1.times.2 or a 1.times.3 coupler, is formed by first terminating the fibre end which is to form that redundant port, and then coupling the fibres e.g. by fusion.

Abstract: An optical fibre cable especially for submarine use has a core (1) surrounded by a layer (5, 6, 7) of strength members which include both wires (6) and laser-welded metallic tubes (7) containing the optical fibers (5).

Abstract: A comb-like support structure for optical cords has slots of uniform width having resiliently-compressible walls which grip frictionally the cords. Intermediate portions of the cords are simply pushed into corresponding slots from one end. The cord support is conveniently mounted in one wall of a distribution frame for optical fibre transmission systems.

Abstract: An optical fibre cable includes, within a surrounding cover, at least one optical fibre extending longitudinally, and a hydrogen-absorptive material comprising a metal cation and an organic anion, preferably dispersed or dissolved in a water-blocking compound. The hydrogen-absorptive material may be a metal salt, preferably a silver salt, of a carboxylic acid, or else a metal loaded ion exchange resin.

Abstract: An optical fibre cable, especially an aerial cable, has, within an outer sheath four or five strength members with at least one optical fibre package accommodated in an interstitial space formed by the strength members. Such a cable can be constructed to have sufficient tensile strength for installation between towers up to 1000 meters apart.

Abstract: A distribution frame for an optical fibre transmission system comprises a cabinet incorporating at each side at least one side panel supporting a surplus length of cable, a pair of inner panels spaced from the side panels and organizer trays, arranged to accommodate surplus lengths of fibres from the cables, supported between the inner panels, the latter panels also supporting couplers for enabling the cable fibers to be connected to further fibres, the ends of which are accommodated in the spaces between the inner and side panels.

Abstract: In the manufacture of a cable having a plurality of filamentary members such as wires, optical fibres or the like within an extruded thermoplastic sheath the members are twisted into a periodically reversing helical configuration immediately prior to the extrusion of the sheath around them, and the extruded sheath is rapidly cooled on emergence from the extruder head so as to cause the extrudate to set and thereby retain the members in the twisted condition.

Abstract: An optical fibre cable contains a quantity of hydrogen trapping material distributed along it for example within each channel containing one or more optical fibres.

Abstract: An optical fibre cable has a plurality of longitudinally extending closed channels (6) formed in a protective cover, and each bounded by part of the outer wall (5) of the cover, wherein said wall (5) is formed with at least one region (8) of reduced thickness extending along a channel (6) so as to form a line of weakness which facilitates penetration of the cover to give access to the optical fibre (7) or fibres within the channel (6). A rip cord (9) may be embedded in the wall (5) so that by pulling the rip cord (9) a slit (10) is formed in the wall (8).

Abstract: In the production of an optical fibre cable a core (3) of thermoplastics material is extruded with a plurality of longitudinally-extending grooves (15) in its outer surface around an electrical conductor (1) and is initially cooled: then following the introduction of one or more fibres (11) in at least one of the grooves the core assembly is passed through an induction heating unit (17) in which the conductor is heated to an extent sufficient to soften at least the adjoining region of the core, and the core is twisted to cause the grooves to take up a helical or periodically reversing helical path, and is again cooled to leave the grooves in that condition.

Abstract: In a telephone line feeding arrangement, the line current is monitored by a multi-resistor network (R.sub.p R.sub.s) and the output of the network applied to the inputs of an operational amplifier (A3). The output of this amplifier, which is a voltage whose value depends on the line current, is compared by a comparator (A4) with a reference voltage (V.sub.R) to produce a control voltage for a variable voltage (VVS), the output of which provides line feeding voltage.In an alternative, the monitoring is effected by connecting the two line wires each via a resistor to one of the inputs of an operational amplifier (A6) whose output is a voltage dependent on line voltage. This voltage is applied to an input of another operational amplifier (A7) where it is in effect added to a reference voltage (V.sub.R). The output of this amplifier (A7) is used to control the variable voltage source (VVS), which in turn controls a constant current source (CCS) whose output provides line current.

Abstract: In a fully digital telephone switching system, a digital switch may serve a number of PCM sub systems each having separate forward and reverse highways and each serving a number of subscribers' lines. The highways are grouped in blocks of eight, from which intelligence is received in serial byte-interleaved form and converted by serial-parallel converters to parallel byte-interleaved form. While in this form they are switched to other channels and applied to a super-multiplexer which they leave in parallel byte-interleaved form from which they are restored by another converter to serial byte-interleaved form for application to the switch's outputs. For the reverse channel the arrangement is the reverse of the above, i.e. serial-parallel conversion, switching and parallel-serial conversion to the line multiplex highways. For local calls a loop-back connection is provided via a fixed delay of half a frame time. Thus, if the outputs fail, the arrangement can still handle local calls.