Abstract: A stranded wire strength member (2, 3) has a cable locking element (4) lying in the interstice between adjacent wires of the strength member. The locking element is of mild steel and has a surface coating (4a) of carbide grit which locks the adjacent wires of the strength member together in the region of a welded joint, to improve the load sharing capacity of the wires of the strength member.

Abstract: In order to eliminate the effect of water attack on silica optical fibres, the fibres are provided with a surface layer of silicon nitride or silicon oxynitride. The method proposed includes direct nitridation. This may be achieved by adding a nitriding atmosphere to the drawing furnace gases, or to the reactive gases (TiCl.sub.4 and SiCl.sub.4) incorporated in the flame of an oxyhydrogen torch for the formation of a compressive silica/titania layer on an optical fibre by a glass soot deposition and sintering process.

Abstract: A cable burying device (3) comprises several heavy hollow tapered elements (7, 8) coupled to each other (7A, 7B, 8A, 8B) to provide limited flexibility, which is towed along the seabed and which digs a trench, the cable (1) passing through the length of the device to become buried in the trench. A guide tube (2) to guide the cable (1) from the ship to the burying device (3) has a flexible lattice construction (FIGS. 6, 7, 8) which can be folded flat for ease of storage on the ship.

Abstract: A method of installing a cable, particularly but not exclusively in a duct filled with flowing liquid, wherein, as the cable is deployed, the strain in the cable is determined by sending a signal down the cable and receiving a signal back from the cable. The speed of deployment is adjusted according to the strain detected. Preferably the system is applied to optical cables, and a radio frequency signal is modulated on an optical carrier. optical connection to the cable on the rotating drum is made via an optical slip-ring. The front end of the cable has a silvered end termination for reflecting the modulated signal back along the fibre to be detected by an optical receiver, and there is a vector voltmeter for determining the phased difference between the signals to thus determine the strain in the cable.

Abstract: A non-contacting method of measuring the electrical resistance per unit length of a filament, such as a carbon-coated optical fibre, makes the filament the inner conductor of a co-axial transmission line and measures a propagation characteristic of that line. The transmission line may be divided into seven sections, with a signal injected on the second section, and a comparison of the resulting signals appearing on the fourth and sixth sections being used in a feedback loop to control the injected signal frequency in such a way as to hold constant either the relative amplitudes or the relative phases of the signals appearing at the fourth and sixth sections.

Abstract: In an optical fiber transmission system, signals are transmitted along a fiber optic path (11) in the form of substantially dispersion-free solitons. The transmission path includes a number of optical amplifiers (12) each of which determines, from the transmitted soliton signal purity, a gain control signal which is fed back to a previous amplifier in the path. This ensures soliton purity and optimizes the transmission power.

Abstract: A fractional-N frequency synthesizer having a programmable divider and a control circuit therefor, wherein said control circuit incorporates a digital delta-sigma modulator operating as an interpolator.

Abstract: An optical fiber is provided with a vitreous carbon coating by the pyrolysis of propadiene promoted by the retained heat of the fiber immediately after it has been drawn from preform.

Abstract: A fully self-aligned polycrystalline silicon emitter bipolar transistor. Self-alignment of the p.sup.+ base contact (12) is achieved by using oxidized sidewalls (8) (sidewall spacers) of the emitter mesa (7) as part of the p.sup.+ base contact implantation mask. Collector contact (13) alignment can be achieved using oxidized sidewalls (17) of polycrystalline silicon alignment mesas (14) defined in the same polysilicon as the emitter mesa (7) but deposited on oxide (2) rather than the implanted base region (5).

Abstract: An hybrid laser source has a ring structure including the optical path in a semiconductor amplifier chip (1) and optical fibres (2, 3 and 4). The fibre (2) is rare-earth doped and provides an additional gain medium in the ring, the chip providing its own gain medium. The two gain media are interactive and when the chip input current is modulated the source produces relatively high peak power ultrashort pulses (FIG. 1).

Abstract: A method of providing a through-hole connection between conductive layers of a multilayer circuit board assembly whose thickness is liable to expansion and contraction is described. The method includes inserting into through-holes in adjacent boards a tubular flexible conductive member and expanding that member in a position intermediate its ends to engage the through-holes. The boards are then urged together to further expand the tubular member so as to retain that member in the through-holes. Typically the conductive member comprises a tubular braid.

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: A joint for an optical cable has a tapered hollow insert (26) with high friction surfaces (26D) so that after jointing the optical package, the cable strength members (6A 6B) can be clamped onto the high friction surfaces of the insert by a wedging action. The surfaces prevent strength members moving axially and imposing longitudinal strain on the jointed package, and the arrangement is such that the differential strain between the strength member layers are minimized if not eliminated.

Abstract: A method is disclosed for addressing a matrix-array type liquid crystal layer. The cell has a plurality of pixels which are defined by regions of overlap between two sets of electrodes which sandwich a liquid crystal layer, each pixel having two states. The response time for switching between the two states is dependent upon the voltage across the liquid crystal layer, with a minimum occurring at a particular voltage. The method includes applying a strobe waveform to a selected member of a first set of the electrodes while a data waveform is applied to each member of the second set of electrodes. A waveform for switching a pixel defined by the selected member comprises a switching pulse of a given voltage magnitude and given duration. A waveform for not switching a pixel defined by the selected member comprises a non-switching pulse of a voltage magnitude greater than the given voltage magnitude of the switching pulse and a duration less than the given duration of the switching pulse.

Abstract: A passive distribution system for electromagnetic radiation using waveguides and couplers wherein radiation from a source is distributed to a number of destination points, including means at destination points for determining the power levels received at the destination points and means for transmitting from the destination points to the source location information representing said received power levels.

Abstract: A joint assembly for an underwater optical fibre cable provides a limited-movement sliding clamp arrangement for the kingwire ends (9, 11). The sea casing provides the main tensile strength member of the joint and a split liner provides the main compressive strength of the joint. Tapered clamps (22, 12, 27) are incorporated into bulkheads of the joint assembly and coupled with ring nuts which screw into the sea casing and cause the bulkhead to abut the split liner. First and second parallel storage plates (1,5) store excess fibre and fibre splices.

Abstract: A one-dimensional reflective-type diffraction grating is formed in a slab waveguide by a one-dimensional array of wells formed with substantially perpendicular walls.

Abstract: An off-line processor arrangement for a broadband accelerated convergence adaptive antenna array wherein signals from a plurality of antenna elements are applied to respective identical tapped delay lines (T) the outputs of which are fed through individual signal weighting means to a beamforming network (BFN), the arrangement including one or more lattice filter means (LF) to which the auxiliary antenna element signals are applied together with the output response of the beamforming network to compute sets of weight correction vectors (* W) with which to update weight coefficients and means for storing said updated coefficients, said stored coefficients being applied to the individual signal weighting means to weight the outputs of the tapped delay lines.

Abstract: An optical fibre gland for a submerged repeater comprising an insulating body (1) having a bore (4) accommodating a pressure tube (5). A high pressure end fitting (8) is secured to the tube and the body and a low pressure end fitting (12) is secured only to the tube. The tube and fibres are water and gas blocked and the construction is such as to enable the gland to operate satisfactorily over a wide temperature range.

Abstract: A cable anchorage for anchoring a submarine cable wire strength member comprises conically tapered parts (2,4,5), at least one of which has a surface (2C, 4B), roughened by tungsten carbine grit evenly distributed over and firmly bonded to the surface, prior to assembly of the parts of the anchorage. The grit size is chosen so that a sufficient locking mechanism is achieved but the grit indentations in the wire strength member are not deep enough to weaken the wires (3B, 3C).