Abstract: A flag anti-wrapping device for reducing friction and side loading, which are common causes of flag wrapping. The flag anti-wrapping device includes an inner race, an outer race, a plurality of roller bearings, and a cap. Roller bearings are placed in an annular cavity, which is defined by the outer race having an inner circumference with a diameter larger than an outer diameter of the inner race. Thus, a flag may rotate about a flagpole with reduced friction and side-loading. Thereby, eliminating side load binding and reducing wrapping of the flag about the flagpole.

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 laser has a resonant cavity defined by a pair of mirrors (6, 10) butted to respective ends of a 3 m fluorozirconate optical fibre (14). The fibre (14) has a .DELTA.n of 0.014 and a cut-off wavelength of around 790 nm and is doped to about 500 ppm (weight) with erbium ions. An optical pump source (12) provides a pump signal at 971 nm which excites the erbium ions into the .sup.4 S.sub.3/2 energy level to provide lasing at about 546 nm. The laser may alternatively be pumped by a pump signal in the band 791 nm to 812 nm, preferably 801 nm. The pump source is preferably a high power semiconductor laser (16).

Abstract: An 850 nm laser and/or amplifier comprises a single mode fluoro-zirconate optical fibre (20) doped with Er.sup.3+. CW operation of the normally self-terminating lasing transition .sup.4 S.sub.3/2 to .sup.4 I.sub.13/2 is achieved by applying excitation energy at 801 nm which both maintains a population inversion between the lasing levels and also populates the upper lasing level by a two-stage process of excitation to the .sup.4 I.sub.9/12 level from the .sup.4 I.sub.15/2 ground state and then to .sup.2 H.sub.9/2 level by ESA.

Abstract: A laser has a resonant cavity defined by a pair of mirrors (6, 10) butted to respective ends of a 3 m fluorozirconate optical fibre (14). The fibre (14) has a .DELTA.n of 0.014 and a cut-off wavelength of around 790 nm and is doped to about 500 ppm (weight) with erbium ions. An optical pump source (12 ) provides a pump signal at 971 nm which excites the erbium ions into the .sup.4 S.sub.3/2 energy level to provide lasing at about 546 nm. The laser may alternatively be pumped by a pump signal in the band 791 nm to 812 nm, preferably 801 nm. The pump source is preferably a high power semiconductor laser (16).

Abstract: A laser amplifier having an improved pump efficiency for a given pump power comprises a pump source (46) longitudinally coupled at a plurality of coupling points (47, 48, 49) to an optical fibre (41). By thus coupling the pump power into the fibre (41), a fraction of the pump power is applied to the fibre (41) at each of the coupling points (47, 48, 49). A significant improvement in pump efficiency may be achieved in this way.

Abstract: The invention relates to laser systems of the type comprising optical fiber amplifiers. A laser system comprises a first laser 1 and a second laser 2. The second laser 2 is pumped at a first wavelength .lambda..sub.1 and caused to lase at a second wavelength .lambda..sub.2. The first laser 1 has absorption bands .lambda..sub.1 and .lambda..sub.2. The output .lambda..sub.2 of laser 2 and the remnant pump at .lambda..sub.1 are coupled and both are used to pump the first laser 1, thus causing laser 1 to lase at a third wavelength .lambda..sub.3.

Abstract: An optical device comprises an optical waveguide, such as a single mode optical fiber (11), underlying a first layer (2) of material, such as a thin film, which has a refractive index higher than the refractive index of the waveguide (11) and which forms a planar waveguide capable of supporting and guiding at least one propagation mode of a higher order than, but matching the phase velocity of, the propagation mode or modes in the underlying waveguide. A reflection diffraction grating (4) is provided on or adjacent to the surface of the first layer (2) remote from the waveguide (11). The arrangement is such that an optical signal which is coupled from the waveguide (11) into the first layer (2) is reflected by the reflection diffraction grating (4) and is coupled back into the waveguide.

Abstract: An optical coupler device comprises a waveguide structure underlying a first layer of material which has a refractive index higher than the effective refractive index of the waveguide structure and which is capable of supporting propagation modes of a higher order than, but matching the phase velocity of, the propagation mode or modes in the underlying waveguide structure, said layer thereby forming a wave guiding structure.

Abstract: A selective filtering device for use in optical communications systems takes the form of a transversely coupled Fabry-Perot interferometer. One described embodiment comprises a first length of monomode optical fiber transversely coupled to a second fiber in a coupling region. One end of each fiber at opposite respective ends of the coupling region is provided with a suitable highly reflective surface, or example, an evaporated gold/aluminum deposit. In operation, a light input may be modified by the resonant cavity behavior of the Fabry-Perot cavity formed between the mirrored ends to provide filtered or enhanced outputs. The outputs may be further modified by alternative or additional light input via the ends of the fibers.

Abstract: Apparatus for cleaving an optical fibre (115) under axial tension, is provided with a cleaver blade (116) which is mounted as part of a rotatable cleaver assembly. The assembly is balanced about its axis of rotation and, as described, comprises a wheel (117) mounted on an axle (138). The cleaver blade (116) is attached to an arm which extends radially from the wheel (117). A hair spring (304) drives the assembly. The cleaving apparatus finds particular application in cleaving monomode fibres under normal working, rather than laboratory, conditions.

Abstract: Features of the endface of a dielectric member are assessed by means of a reflected diffraction pattern.A plurality of light beams 6, 7 which intersect in a region containing the endface 8 can be used to generate a diffraction pattern 10 which subtends an angle of at least 180.degree. at the endface 8. Such a diffraction pattern 10 contains information about the endface 8 and may be used, in particular, to locate the plane in which the endface 8 lies.Embodiments of the invention find particular application in the measurement of endface angles of optical fibres.

Abstract: A technique for aligning and coupling dielectric optical waveguides comprises threading the end of a waveguide through the central opening of a triad ball connector and forming by fusion a generally spherical glass bead on the end of the waveguide using, for example, an electric arc. The waveguide is then drawn back so that the bead contacts the balls of the triad connector to accurately locate the waveguide. The bead acts as a locating element and also has beneficial focussing properties.

Abstract: A pair of optical fibres which are to be joined are located with their end portions in coupling elements one of which is transparent to light. The coupling elements are located such that the ends of the fibres are in approximate alignment. Light is transmitted along one fibre so that it is received by the fibre in the transparent coupling element. Light which is not coupled into the core of the fibre is sensed by a sensor and the relative position of the fibres is adjusted until the level of sensed light is a minimum. The sensing of the light is carried out at positions spaced angularly about the waveguide so that an indication of the direction of any misalignment is obtained. The coupling elements are then secured in this position. The adjustment of the fibres can be carried out using a linear translation stage and a microprocessor which controls the stage in accordance with signals from the sensor.

Abstract: Features of the endface of a dielectric member are assessed by means of a reflected diffraction pattern.A plurality of light beams 6, 7 which intersect in a region containing the endface 8 can be used to generate a diffraction pattern 10 which subtends an angle of at least 180.degree. at the endface 8. Such a diffraction pattern 10 contains information about the endface 8 and may be used, in particular, to locate the plane in which the endface 8 lies.Embodiments of the invention find particular application in the measurement of endface angles of optical fibres.