Abstract: A ferroelectric liquid crystal cell matrix address scheme that uses bipolar strobe pulses (20) to co-operate with bipolar data pulses (21,22) in a way that it can switch pixels into different states in a single refreshing not preceded by page blanking.

Abstract: A quantum confined Stark effect (QCSE) optical modulator element has one or more quantum wells each bounded by assymetric barriers. This provides a device in which the direction and magnitude of the electric field induced absorption edge shift corresponds to the polarity and intensity of an applied electric field.

Abstract: A one-shot method of making an optical fiber package (FIG. 1) for a submarine cable. A plurality of fibers (1) are fed into a space delimited by one or more elongate elements from which a tubular structure (3) can be formed, for example a C-section. A liquid filling material, such as a two-part exothermic curing polyurethne, mixed by static mixer (16), is injected into the C-section which is then closed by a die (17). The filling material rapidly cures to a resilient solid (2) in which the fibers are embedded before hauler (18) is reached. The fibers are spaced apart from one another and the tubular structure by means including a guide structure (14,15) as they enter the C-section and this is maintained in the cured material.

Abstract: An optical logic device consists of a bistable liquid crystal layer (BOD 1) of the thermally-induced birefringent (TIB) type settable by one or more write beams and rfead by a beam of a different wavelength or different light polarization. Thus the read and write beams are optically decoupled. Two such devices (BOD 1 and BOD 2) in tandem form a 3-input AND gate. Here beams A and B are write beams for the first device, (BOD 1), and beam C is the read beam for the first device. For the second device (BOD 2) the write beams are the output of the first device (BOD 1) and beam D, the read beam being beam E. The two read beams have different wavelengths from the write beam. In a second version, the liquid crystal layer is on the base of a prism via which the beams reads it. Write beams go right through the layer, while a read beam is "reflected" from the layer but is modulated by the state thereof. This is an OR gate. Logic assemblies can use combinations of such AND or OR gates.

Abstract: An extrnal fibre drawing furnace is maintained at or close to its normal working temperature while contaminants are removed between fibre pulls. Either a removable insert, replaceable gas port assembly, or cleanable gas transfer duct, enable this to be achieved while the furnace is maintained at or near its operating temperature, so that the down time is of the order of minutes rather than hours.

Abstract: An optoelectronic transducer (1) is connected with a fiber optic tail (22) by providing a casing (3) around the transducer having a flat wall (9) and by providing a termination body (20) on the fiber (22) with a thin wall flange (20A), aligning the optical axes (11, 29) and laser welding the flange to the casing.

Abstract: An arrangement for the deployment of towed aircraft decoys comprising a reel with a hollow hub or flange rotatably mounted on a support, the reel being wound with a composite tether-wire consisting of an optical fiber cable reinforced with a strain member, one end of the tether-wire being anchored to the hub or flange, and within the hub or flange a spiral spring member one end of which is anchored to the hub or flange and the other end of which is anchored to the support, the spring member having attached thereto a flexible optical fiber such that the fiber conforms to the configuration of the spring when the spring is wound or unwound according to rotation of the reel relative to the support, the flexible fiber being connected at one end with the anchored end of the optical fiber cable on the hub or flange and at the other end with an optical connector means on the support, whereby unreeling of the tether-wire results in rotation of the reel and consequent winding up of the spring.

Abstract: A process for fabricating a CMOS compatible bipolar transistor is described. The transistor, which is of the polysilicon emitter type, is fabricated by forming a p-type layer in a well, providing a polysilicon emitter in contact with the layer, using the emitter as a mask to implant p.sup.+ -type base contact regions, and applying contacts to the device.

Abstract: A semiconductor structure is configurable via a customizing mask either as a varicap diode or as a polysilicon emitter bipolar transistor. The structure forms part of an integrated circuit providing e.g. a voltage controlled oscillator for a crystal frequency standard.

Abstract: Isolation trenches are formed in a semiconductor, e.g. silicon, substrate by selectively doping the substrate and preferentially oxidizing the doped material. Typically the dopant is arsenic or phosphorus and preferably the substrate is doped to a level of at least 5.times.10.sup.19 cm.sup.-3.

Abstract: A multi wavelength optical network including a plurality of wavelength multiplexed nodes each having a single frequency optical signal transmitting means (13) and a multi wavelength optical signal receiving means (15), an optical transmission network including a passive optical coupling means (12) interconnecting said nodes whereby single frequency signals transmitted from each node are propagated via the coupling means to all the nodes, each node also including wavelength demultiplexing means (14) through which received signals are applied to the multi wavelength receiving means and timing and control means (17, 18, 19) arranged to control the timing of signals transmitted by the node over the network so that the signals from all the nodes are synchronous at the coupler.

Abstract: An optical sensor uses a torsion-mounted thin silicon paddle (1) with magnetically soft material on its back. A light beam falls on the front face and part of the beam is reflected to a photo-diode (4) whose output drives a current in a magnetizing coil (5). The magnetic field thus produced rotates the paddle out of the beam, which cuts off the light to the photo-diode. Thus the paddle oscillates with an amplitude which depends on the strain due to the torsion mounting. This modulates the light beam, and if they have different resonances several such sensors can share the same beam with a common read-out.

Abstract: A device for producing an optical delay in an optical signal having variable optical frequency, the optical delay varying with the optical frequency, comprises a chirped Bragg reflector formed in an optical fiber and a directional coupler for separating the reflected signal from the input signal. One application of the device is for chromatic dispersion equalization. Various methods of manufacturing the chirped Bragg reflector are described.

Abstract: An integrated circuit structure has a number of device areas each of which is configurable in a subsequent customizing process as a field effect transistor, a bipolar transistor or as a pair of those devices. Configuration of the structure is determined by correspondingly selective etching of a polysilicon layer disposed on the structure.

Abstract: A 1.times.N single mode optical waveguide coupler comprises a single input optical fibre (1), a slab-like mixer waveguide (3) and a plurality (N) of output optical fibres (2). As a result of interference effects light introduced into the mixer waveguide (3) via the centrally located input fibre (1) produces a linear array of output spots at various intervals along the length of the mixer waveguide. The length of the mixer waveguide is chosen such that the output optical fibres are aligned with one such array of output spots. The fibres may be adiabatically tapered to a smaller diameter in order to increase their modal spot size.

Abstract: In a transducer, e.g. a pressure transducer, the sensing element comprises a torsional oscillator provided with magnetic means for feedback of signals to maintain oscillation. Typically the sensing element is formed by selective etching from a body of single crystal silicon.

Abstract: A successive approximation analog to digital converter including at least one superconducting loop (FIG. 3-30; FIG. 8-68). Superconducting loops (61-64) may be used to store flux quanta used as reference levels in a digital to analog converter of the analog to digital converter. Alternatively, non-superconducting reference inductors (FIG. 3-38) can provide flux quanta reference levels. Switchable screens (34; 66) are interposed between the flux quanta stores and lobes (31; 74) in an addition/subtraction superconducting loop (30; 68). An analog signal is sampled and the corresponding magnetic flux coupled to a sensing lobe (32; 71) and concentrated at a flux concentrating lobe (33; 72). The reference fluxes are selectively coupled into the addition/substraction superconducting loop until a magnetometer (40;73) indicates zero net flux through the concentrating lobe, this corresponding to completion of the conversion.

Abstract: An edge emitting light emissive diode for coupling light into single mode fibre has at its front end a structure (7) similar to that of a ridge laser, this structure being terminated at its rear end with a planar region (8) which is unpumped.

Abstract: An apparatus for pulsed plasma treatment of a substrate surface includes means for removing spent gas from a region adjacent the substrate for each pulse. The apparatus may also include means for sweeping an intense plasma region across a substrate surface. Rapid gas exchange is provided by pressure pulsing the gas admission. This facility also provides means for rapidly alternating different gases.

Abstract: A phase modulator circuit includes a pair of similar long-tailed pair transistor amplifiers (TR11, TR12 and TR13, TR14) to which sinusoidal signals are fed. The transistor pairs form the collection loads of a further long tailed pair (TR21, TR22) fed with a modulator signal. The circuit generates an output of constant amplitude but modulated in phase in correspondence with the modulated signal. The circuit may be used in the supervisory unit of a telecommunication repeater.