Abstract: Apparatus for fabricating fused optical fibre devices comprises a furnace provided with an electric heating element (5). A heat-distributing insert (7) is provided within the heating element (5), the heating element and the insert being sized and shaped to define a heating chamber for an optical fibre arrangement. The apparatus includes means for passing electric current through the heating element (5), and means (8) for supplying and maintaining an inert atmosphere within the heating chamber.

Abstract: An optical fibre feedthrough in which a polarization maintaining (PM) fibre is sealed within a metallic sleeve by a glass seal. The seal applies asymmetric stresses to the fibre which is orientated so that they reinforce its PM properties. This arrangement reduces the manufacturing tolerances needed to avoid destroying the PM properties of the fibre associated with symmetric stress seals. It has application to packages for opto-electronic components. A double optical fibre feedthrough is also disclosed.

Abstract: Method and apparatus for fabricating fused optical fibre devices includes a furnace provided with an electric heating element. A heat-distributing insert is provided within the heating element, the heating element and the insert being sized and shaped to define a heating chamber for an optical fibre arrangement. The method includes passing electric current through the heating element, and supplying and maintaining an inert atmosphere within the heating chamber.

Abstract: An electro-optic device, such as a Mach-Zehnder interferometer or a directional coupler, has a power dissipating electrode structure and a ground plane electrode, and is switchable between first and second distinct states by the application of respective first and second potentials to the power dissipating electrode. Thermally induced instabilities are minimized by biasing the ground plane electrode such that the first and second potentials are of substantially equal magnitude but of opposite sign. The power dissipating electrode may be a travelling-wave electrode connected to a 50 ohm transmission line.

Abstract: A transimpedance pre-amplifier circuit is arranged to have a complex pole response resulting from the interaction of the open-loop pole with the pole associated with a circuit feedback. The pre-amplifier circuit includes a transistor with a load capacitor connected in the transistor output circuit to determine the open-loop pole. The feedback includes a resistive element. The first stage of the pre-amplifier comprising the transistor may be followed by one or more further amplifying stages. The feedback to the input of the first stage may be from the output of one of the further stages. A receiver incorporating the pre-amplifier circuit includes only post-amplifiers connected to receive the output of the pre-amplifier. The response of the pre-amplifier makes it unnecessary to include a dedicated passive filter in the receiver and the post-amplifiers can have smaller bandwidths than in conventional receivers.

Abstract: In electro-optic waveguide devices such as directional couplers and Mach-Zehnder interferometers having travelling-wave electrodes which overlie the waveguides, temperature sensitivity is reduced by arranging the ground plane electrode to overlie only part of the width of its associated waveguide portion. The invention has particular application to z-cut lithium niobate.

Abstract: An optical fiber switch in which the switching force is applied directly to the fiber. A biasing force, generated by a bending of the fiber, is exerted on the fiber in a direction tending to urge the same toward the bottom of a first groove. The switching force is applied transversely to the direction of the biasing force, and moves the fiber out of the first groove and into a second, adjacent groove. When in the second groove, the biasing force on the fiber urges the same toward the bottom of the second groove.

Abstract: A method of making an opto-electronic component (13) comprises inserting a pre-assembled device carrier (1) into a mould, filling the mould (2) with light and/or thermally curable material, optically aligning the device assembly and, on achieving optical alignment, at least partially curing the material.

Abstract: A travelling wave optical modulator comprises a Z-cut lithium niobate substrate on which is formed a proton exchanged optical waveguide and a travelling wave electrode. The optical waveguide is removed from the electrode intermittently to bring an optical signal in the optical waveguide back into phase with an electric field passing along the electrode. The optical signal is delayed relative to the electric field thereby allowing modulation of the optical signal by a non-periodic electric field. The optical waveguide is defined within the boundaries of the top surface of the substrate.

Abstract: A technique for assembling semiconductor devices in which semiconductor elements, especially lasers or LEDs, are mounted on a first packaging element such as a heat spreader that is mounted on a second packaging element such as a heat sink. Handling of solder preforms is avoided by coating at least one of each of the pairs of surfaces to be brought into contact with a layer of solder and heating the assembly to melt both solder layers in a single operation. In a preferred embodiment a heat spreader is coated in solder on both sides and interposed between a semiconductor element and a heat sink and the assembly is heated. Molybdenum may be used as a layer to aid wetting and adhesion and gold/tin solder may be used. Slightly different solidification temperatures and compositons for the layers may result from different take up of metallization layers from the components into the solder.

Abstract: An optical transmitter assembly comprises a laser (2) and an optical detector (4) arranged to receive light output from the laser (2) indirectly via a spherical lens (3). The source (2) and the detector (4) are mounted on a common support structure (1), and the lens (3) is mounted directly on the detector (4).

Abstract: A method of making an opto-electronic component (13) comprises inserting a pre-assembled device carrier (1) into a mould, filling the mould (2) with light and/or thermally curable material, optically aligning the device assembly and, on achieving optical alignment, at least partially curing the material.