Abstract: A transmission line, such as an optical fiber (or wire) transmission line, is installed by first installing a conduit having one or more bores and subsequently inserting flexible, lightweight optical fiber members containing the optical fibers into the bores. The optical fiber members are propelled by employing the fluid drag of air, or another suitable gas, passed at high velocity through the bores.

Abstract: A transmission line, such as an optical fiber (or wire) transmission line, is installed by first installing a conduit having one or more bores and subsequently inserting flexible, lightweight optical fiber members containing the optical fibers into the bores. The optical fiber members are propelled by employing the fluid drag of air, or another suitable gas, passed at high velocity through the bores.

Abstract: A transmission line, such as an optical fibre (or wire) transmission line, is installed by first installing a conduit having one or more bores and subsequently inserting flexible, lightweight optical fibre members containing the optical fibres into the bores. The optical fibre members are propelled by employing the fluid drag of air, or another suitable gas, passed at high velocity through the bores.

Abstract: An optical communication system includes a head-end station, an optical fibre network and a number or sensors and actuators connected via the network to the head-end station. The head-end station includes one or more broadband sources and is arranged to output a broadband signal onto the network. The sensors modulate the broadband signal received from the head-end station and return narrowband components of the signal via the network to the head-end. There the different narrowband components are detected, for example using a demultiplexer and the resulting signals processed by control electronics. The head-end station also includes an optical circuit arranged to split a signal from a broadband source into different narrowband components. Electro-optic modulators (FOM) modulate the different narrowband components and the resulting narrowband signals are output onto the fibre network and transmitted to the actuators. The electro-optic modulators (FOM) are operated by the control electronics.

Abstract: A filter has a preselected attenuation/wavelength characteristic, in which spatially separated parts of the filter attenuate different wavelengths. The spatially-separated parts have different attenuation characteristics to attenuate different wavelengths in a predetermined manner to provide a selected attenuation/wavelength characteristic. In one arrangement an interference type filter includes a grating, the pitch of which varies spatially. In one instance, the structure to determine the proportion of radiation subject to interference includes a grating of spatially-varying effectiveness, but alternatively it may include an attenuation filter, the attenuation effect of the attenuation layer varying spatially. In another arrangement, the filter may include structure to separate received radiation into a spatially-disposed spectrum, and to attenuate different parts of the spatially-disposed spectrum in such a manner as to provide the selected attenuation/wavelength characteristic.

Abstract: An optical network having a spatially-multiplexed plurality N of optical waveguides is employed in conjunction with another, non-spatial signal multiplexing technique (e.g., frequency multiplexing) defining a plurality M of further optical signal channels thereby providing an enhanced number N.times.M of optical signal channels that can be selectively coupled to by optical signal processors.

Abstract: A transmission line, such as an optical fibre (or wire) transmission line, is installed by first installing a conduit having one or more bores and subsequently inserting flexible, lightweight optical fibre members containing the optical fibres into the bores. The optical fibre members are propelled by employing the fluid drag of air, or another suitable gas, passed at high velocity through the bores.

Abstract: A wavelength-selective arrangement interacts with optical radiation propagating in a transmission medium. The arrangement includes a selector member made of a polar organic material which exhibits piezoelectric properties, the selector member having an interaction surface for interacting with the radiation. The selector member is provided with structure for propagating surface acoustic waves along the interaction surface so as to create a grating and thereby determine its interacting properties in relation to the wavelength of the radiation, in a selectively variable manner.

Abstract: An optical network includes an erbium-doped silica-based optical fibre having a D-shaped cross-section. The wave-guide carries information signals at 1.53 .mu.m from a signal source and provides amplification to the information signals when pumped by an optical pump source operating at 0.994 .mu.m. Optical signals are tapped from the waveguide by means of evanescent couplers. The waveguide provides amplification to at least partially restore tapping loss to the information signal due to the optical taps. The core of the optical waveguide is chosen to substantially minimize the spot size of signals at the wavelength of the pump source so as to provide preferential extraction of the information signal in order to leave the pump source substantially undisturbed to be able to pump regions of the amplifying waveguide beyond the optical tap.

Abstract: Apparatus for conditioning of fluids such as fuel compositions. The fluid to be treated is brought into contact with an alloy comprising zinc, manganese, copper, a precious metal and silicon. The alloy may be surrounded by one or more magnets to enhance operation.

Abstract: Apparatus and methods for conditioning of fluids such as water, aqueous solutions and fuel compositions. The fluid to be treated is brought into contact with an alloy comprising zinc, manganese, copper, a precious metal and silicon. The alloy may be electrically connected to earth ground during operation.

Abstract: An optical interconnection network includes an optical bus formed by a D-fibre embedded in a thermoplastic substrate with the flat of the D-fibre flush with the top surface of the substrate. A module similarly constructed is dimensioned to be a push fit in a wall structure formed on the substrate with the fibres and in a position to evanescently couple optical signals from one fibre to the other.

Abstract: A transmission line, such as an optical fibre (or wire) transmission line, is installed by first installing a conduit having one or more bores and subsequently inserting flexible, lightweight optical fibre members containing the optical fibres into the bores. The optical fibre members are propelled by employing the fluid drag of air, or another suitable gas, passed at high velocity through the bores.

Abstract: A wavelength selective optical waveguide coupler (1) comprises a first undulatory optical D-fiber (2) and a second optical D-fiber (4) embedded in respective substrates (4,8). The fibers (2,6) are located adjacent one another, the undulations of the fiber (2) defining a set of regularly spaced optical coupling regions. This provides a readily formed coupler able to be accurately set to selectively couple a pre-selected wavelength by relatively coarse macroscopic adjustment.

Abstract: A sheath for optical fibres comprises a compound sheath having an inner sheath of high modulus and density, and an outer sheath layer of low density material. The outer sheath layer may be of foamed polyethylene and the inner sheath of polypropylene, both conveniently formed by extrusion. Such fibre members are installed by first installing a conduit having one or more bores and subsequently inserting the flexible, lightweight optical fibre members containing the optical fibres into the bores. The optical fibre members are propelled by employing the fluid drag of air, or another suitable gas, passed at high velocity through the bores.

Abstract: A method and apparartus for setting the orientation of an optical fibre (6) having at least one planar section extending along its length comprises a light source (3) for generating a beam of light which impinges on the fibre (6). Light reflected by the fibre is detected by a light detector (5) and the fibre is rotated by means of a tube (1) into which it is inserted while the intensity of the detected light is monitored. When the intensity becomes a maximum then the planar face is facing in a known direction.

Abstract: An optical switch which selectively transmits or does not transmit light from an input optical fibre (10) to an output optical waveguide (11,12) has one of the input (10) and output (11,12) optical waveguides an optical fibre which is flexible and mounted to be capable of movement towards and away from the other, and an electrode (14) arranged to subject the one optical waveguide to an electrostatic field. In use, application of an electrical potential to the electrode (14) causes the one optical waveguide to move in a direction to enable or prevent optical coupling between the waveguides and hence operation of the switch. The optical fibre is a D-fibre so that it is more flexible in that direction is providing the fibre with a degree of self-alignement. It is preferred that the one optical waveguide is entirely electrically non-conducting and that the optical switch includes more than one electrode (14) to provide a non-uniform electrostatic field.

Abstract: A transmission line, such as an optical fibre (or wire) transmission line, is installed by first installing a conduit having one or more bores and subsequently inserting flexible, lightweight optical fibre members containing the optical fibres into the bores. The optical fibre members are propelled by employing the fluid drag of air, or another suitable gas, passed at high velocity through the bores.

Abstract: An optical fibre has a coating of, for example, liquid crystal polymer which causes temperature-dependent stress-induced changes in the optical fibre such as to counteract temperature-induced changes in the transmission delay of the fibre.

Abstract: A method of preparing a junction between the cores of two D-optical fibers comprises bending a first fiber around a curved surface and causing its flat face to face outwards, superposing a second D-fiber on the first fiber, bending the second fiber around the curved surface causing its flat face to fact towards the curved surface, and controlling the lateral position of the superposed fibers on the curved surface to provide a predetermined separation between the cores of the fibers. When both fibers are arranged in a plane normal to the axis of the curved surface the flat faces of both fibers lie strictly parallel to the surface and thus the flat faces of both superposed fibers are substantially in contact with one another so that the cores of both fibers are close together.