Abstract: An optical fibre is provided with a coating by coating the fibre (1) with a coating material (4) on-line with the fibre drawing process (2) and employing a laser beam (6) to locally heat the coating material whereby to change its physical or chemical properties. Metallic glass coated fibres, useful for hermeticity and sensor applications, can thus be achieved in multikilometer lengths by fusing metallic glass forming alloy coatings to a fibre. Alternatively, polymer coatings may be cured by laser beam local heating.

Abstract: Use is made of stimulated Raman emission to induce gain in an optical signal (13) of a first wavelength. The optical signal (13) and a pump signal (14) are synchronously coupled to a length of optical fibre (15). The pump signal is at a second wavelength. The first wavelength corresponds to one Stokes shift from the pump signal. The pump signal is generated by a semiconductor laser (11) and thus only relatively low pump powers are involved in comparison with the conventional use of YAG lasers as the pumps, however significant gain is achieved despite the low pump powers. Preferably the optical fibre (15) has a high Raman cross-section and a low transmission loss, for example GeO.sub.2 doped SiO.sub.2 or pure GeO.sub.2.

Abstract: A mass transport process for use in the manufacture of semiconductor devices, particularly but not exclusively low threshold semiconductor lasers in the InP/InGaAsP system, involves the arrangement of a cover wafer (18) of the material to be grown adjacent to a semiconductor wafer (15) on which the material is to be grown, their disposition together with a crystalline alkali halide (20) in a crucible (16), and heating the crucible, which is almost but not completely sealed, in a hydrogen stream.For the manufacture of InP/InGaAsP lasers and the growth of InP, the alkali halide may comprise KI, RbI or CsI and a controlled amount of In metal (21) may be optionally contained in the crucible (16) to control the balance between growth of InP for defining the laser active region and erosion of InP from other areas of the wafer. Growth is achieved at temperatures comparable with liquid phase epitaxy processing temperatures.

Abstract: Amorphous metallic material in ribbon form is employed to provide hermeticity of cable elements, particularly optical fibres. The metallic glass CuZr has a low permeability for hydrogen, particularly when erbium is included. Thus sealing optical fibres (1) in amorphous metal tubes (3) will prevent increase in attenuation of such fibres when used in submarine cables by preventing contact with hydrogen generated in such cables during use thereof.

Abstract: An optical repeater for a submersible transmission system has a steel housing and a modular assembly carrying the electronic and opto-electronic components. Each module (20) of the assembly has heat conductive electrically insulating devices (30 to 33) secured to the periphery of the module (20) and embracing the inner surface of the housing (1). Each device comprises a resiliently biassed metal element (44).

Abstract: Certain materials (e.g. polymers, glasses) exhibit the photo-elastic effect, whereby when they are subject to stress become birefringent, which influences a light beam passing through the glass. This beam, e.g. from a laser is collimated and circularly polarized as it approaches the glass and is again polarized as it leaves the glass. This stress is applied, according to this invention, by magnetostrictive strips on the glass which are influenced, by the magnetic field to be measured or the AC bias field. A miniaturized arrangement using this principle is described.

Abstract: Optical four wave mixing is provided by interfering two waves on a liquid crystal layer (1) temperature stabilized just beneath its nematic/isotropic phase change transition temperature. The liquid crystal incorporates a guest dye to absorb the light producing a holographic thermal image which is accompanied by a holographic phase image. Illumination of this phase image with a `third wave` of different wavelength is then used to produce the required holographically diffracted `fourth wave`.

Abstract: Low concentration standard aqueous solution for analytical purposes is prepared from a water soluble glass body containing the standardizing material. The glasses are phosphorus pentoxide based glasses and provide release rates, e.g. of Na.sup.++, of 0.01 to 100 micrograms per cm.sup.2 per hour.

Abstract: A multiple output, power inversion adaptive antenna array comprises a number of antenna elements A1-An feeding a cascade beam former structure having groups of decorrelation stages D1.sub.1 -D1.sub.n-1, D2.sub.1 -D2.sub.n-2 etc. The outputs of the first stage in each group are scanned sequentially until the wanted signal is predominant, as determined by a wanted signal recognition CONTROL, at which time scanning of the switch S is halted.

Abstract: A radio receiver for frequency modulated signals in which direct conversion techniques are used to provide zero I.F. quadrature baseband signals I & Q. The I & Q signals are limited (11,12) to form square wave signals and pulse forming networks (13,14) derive pulse sequences the frequencies of which represent the polarity changes in the square wave signals. Each square wave is multiplied (15,16) by the pulse sequence derived from the other square wave to produce a unipolar pulse train. The two unipolar pulse trains are combined (17) to give a digital output signal the frequency of which is equal to the sum of the frequencies of the two pulse trains. Low pass filtering the output signal produces a simulation of the original baseband modulation.

Abstract: An accelerometer comprises a quartz beam 1 having on its upper and lower faces surface acoustic wave devices 2, 3 and 2', 3'. The beam is centrally mounted on quartz spacers 4, 5 which have metallized contacts for the lower SAW device. The spacers are carried on a quartz substrate 6 which is supported on a header 7 forming the base of a dual-in-line package. Mass-loading 8 is provided on each end of the beam 1.

Abstract: A device for the controlled release of an active material into an aqueous medium comprises a porous sintered body of a water soluble glass (11). The pores of the body are filled with a composition (12) consisting wholly or partially of an active material. The device may be provided with a low solubility coating (13). On immersion in an aqueous medium the glass (11) dissolves to become a sponge-like structure having a plurality of convoluted capillaries and from which the active material is released.

Abstract: A Hall effect device for responding to weak magnetic fields uses a small chip of gallium arsenide located between the overlapped ends of two flux concentrators. The spacing between the concentrators may be as small as 95 micrometers. The flux concentrator, which serve to enhance the device's sensitivity are made of amorphous magnetic material, i.e. a metallic glass, which has high permeability.

Abstract: Insulation flaws in electrical components are detected by measurement of electrical leakage before and after immersion in a mobile ionizing solvent, e.g. a lower alkyl alcohol. A significant increase in leakage is indicative of a flaw, e.g. a crack in the insulation.

Abstract: In a small business-type telephone exchange, calls are set up in TDM manner using PCM to convey speech and data if the exchange serves any data terminals. The exchange has subscriber line ports (SLC) each serving two lines and a smaller number of trunk line ports (TLC) each serving a trunk to a local exchange. Each port has a local processor (SIP) with analogue-digital and digital to analogue conversion circuitry (CODEC-FILTER-TSAC). The exchange also has a central processor (CCP) with its associated memories (ROM, RAM, EAROM).The ports and the central processor are interconnected by an intelligence bus (PCM BUS) and a signalling bus (SIG BUS). The central processor (CCP) and the port processors (SIP) co-operate in call setting with all communications between the processors over the signalling bus. During operation the central processor (CCP) polls the ports via the signalling bus (SIG BUS) for ports needing the services of the central processor and also to pass call control information to those ports.

Abstract: Lead-less tantalum capacitors are made using a lead frame (1) formed to provide connection terminals (3,4) separated by an H-shaped aperture (7) and a bent-up anode support station (5). A two-part mould (13,13a) is used to injection mould plastics around the capacitor bodies prior to detaching the capacitors from the lead frame by severing necks (15,16,17,18).A second embodiment has flat connection terminals which are bent around the encapsulated body.

Abstract: A demodulator logic for FSK signals on an RF carrier in a direct conversion radio receiver, wherein the received signals are mixed with a local oscillator to provide quadrature baseband signals, characterized in that the demodulator logic comprises two clocked D-type flip-flops, FF1,FF2 one baseband signal being applied direct to the clock input CK of one flip-flop and inverted to the clock input CK of the other flip-flop, the second baseband signal being applied to the D inputs of both flip-flops, one input Q from one flip-flop being algebraically combined with one output Q from the other flip-flop to provide a demodulator signal output of the receiver, the two flip-flop outputs being chosen so that for a given FSK value they always have the same logic value.

Abstract: Polysilicon elements of integrated circuits, for example gates (24) or interconnects, are provided with metallic silicide layers (26) in order to take advantage of the lower resistivity thereof. The polysilicon elements are defined on an oxide layer (23) disposed on a silicon substrate (20) before polysilicon metallization. After polysilicon metallization the metal and polysilicon are caused to interdiffuse to form silicide layers (26) covering the polysilicon elements (24).

Abstract: A cabling machine for making single optical fibre cable with two layers of stranded armid yarn enclosed in a yarn outer wrap which employs a vertical axis for cabling and uses peripheral pay-off of the aramid yarn (34,39) from bobbins 33 mounted on a pair of separately driven turntables (21,22) and peripheral pay-off of the yarn wrap (45) from a spool (44).