Abstract:
A distributed optical fibre sensor cable, for sensing perturbations suct as pressure, comprises a length of optical fibre (10) and means adapted, in response to the perturbation to be sensec. to mechan,cally deform separate portions of the length of the fibre at sensing elements (11, 12, 13) periodically along their length in order to cause optical power launched into a mode of propagation in the core (14) and guided thereby to be coupled to an unguided mode, for example a cladding (15) mode. The coupling is optical wavelength selective and a number of separate sensing elements are each addressed with a different wavelength ( * 11, * 12, * 13) for spatial resolution along the length of the cable.
Abstract:
A multi-mode radio transceiver comprising a sequence of bi-directional circuit modules including a radio frequency input/output amplifier module (1), a radio frequency/baseband I and Q quadrature channel conversion module (2), an analogue/ digital conversion module (3), a digital signal processor (4, 5), and a digital signal input/output interface (6), with a control means (7) whereby for transmission a radio frequency signal is formed from analogue quadrature I and Q channel components of a digitised signal at baseband and translated to the radio tranmission frequency and for reception the radio frequency signals are transformed into I and Q quadrature analogue components at baseband and subsequently digitised.
Abstract:
57 In order to prevent diffusion of silicon from under a titanium disilicide interconnect (1) and into an overlying aluminium layer (6), the disilicide is selectively nitrided at the points where interconnection between the disilicide and aluminium is required via holes (4) in a silicon dioxide layer (3). The titanium nitride contacts (5) thus formed in a truly self-aligned manner provide a good barrier to silicon diffusion whilst having an acceptable low resistivity.
Abstract:
For launching and recovering tethered remote controlled submarine vehicles a reinforced flexible free-flooding tube 3 adapted to be deployed from a ship is provided with one end of the tube remaining attached to the ship, the tube having passed therethrough an umbilical cable 1 for a remote controlled submarine vehicle. The cable and tube are deployed from a winch drum 2. The upper end of the tube has a conical termination 4 which locates in a support 6 mounted outboard of the ship. The lower end of the tube may have a docking latch to assist in recovery of the vehicle.
Abstract:
On line coating of optical fibre (20) adopts silicon nitride or oxynitride to provide an hermetic seal using chemical vapour deposition. Non-contacting gas seals (3, 4) at the top and bottom of the reaction chamber are so constructed that fibre vibration is avoided, (6) surface flaws are minimised and the coating minimises stress corrosion.
Abstract:
A magnetic angular position sensor having a ferrofluid filled spherical chamber (2) in a cylindrical housing (1), within which floats a body comprising a buoyant core (3) carrying a magnet (4). Hall effect devices (7) are located in recesses (6) in the ends of the housing. The housing also carries a calibration solenoid (8).
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 (1) is collimated and circularly polarised as it approaches the glass (4) and is again polarised 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 miniaturised arrangement using this principle is described.
Abstract:
Infrared optical fibres are provided with hermetic coatings (6) by decomposition or reaction of volatile compounds of the coating material at the surface of the fibre. Materials having melting points greater than the fibre's glass transition temperatures may thus be applied at temperatures lower than the glass transition temperatures. The fibre (1) may be sufficiently hot from a preceding fibre formation (2,3) process in line with the coating process to enable the decomposition or reaction, or additional heating of the fibre by radiation may be necessary in the reaction chamber (7).
Abstract:
A limiting differential amplifier circuit comprises first and second controllable current sources (l 1 , l 2 ) fed with the differential input signal (V m ) and a controllable differential load circuit (l L1 , l L2 ) and a feedback element (β), the feedback element comprising transistors (T 1 T 2 ) sensing the common mode output voltage and a diode (D 1 ) for translating the current generated into a control voltage (V c ) to control the differential load circuit whereby to provide high-voltage gain in the differential signal mode and low common-mode gain.
Abstract:
A joint transform correlator in which a servo-feedback system (18) is included which employs the correlation signal output to electronically modify the representation of the 'archetype' in the reference scene portrayed in one of the spatial light modulators (12) of the correlator to make it a closer match to any 'quarry' discovered in the investigation scene portrayed in the other spatial light modulator (11).