Abstract: A one-time-use camera comprises a film cartridge and a lighttight enclosure which contains the film cartridge and can be opened to remove the film cartridge. Further, the one-time-use camera has a flash unit which is characterized in that a frangible support device for the flash unit is located to be destroyed when the lighttight enclosure is opened to remove the film cartridge.

Abstract: Optical fiber elements, such as narrow pass-band filters, dispersion equalizers, and channel dropping filters, are constructed from 2.times.2 single mode optical fiber fused tapered couplers having formed on one side of coupling regions Bragg distributed gratings in the two fibers from which the coupler is constructed. By making the gratings at a point where the fibers remain fused together in side-by-side contact it is ensured that they lie equidistant from the coupling region.

Abstract: An optical fibre amplifier in which a length of optically amplifying fibre is spliced between a pair of 2.times.2 tapered fused fibre couplers each constructed from a length of amplifier type profile fibre and a length of transmission type profile fibre. In each coupler, one of two constituent fibres has been pre-stretched so as to match the propagation constants of the two fibres within the coupling region of that coupler.

Abstract: A wavelength multiplexing tapered fused fibre coupler is used to splice a second length of optical amplifier fibre between first and third lengths in such a way that pump power bypasses it. The second length is therefore unpumped and acts as a notch filter smoothing out the spectral gain characteristic of the first and third lengths.

Abstract: In the manufacture of a wavelength multiplexing 2.times.2 tapered fused fiber coupler by progressive stretching, the birefringence of the coupler resulting from the progressive stretching is subsequently nulled-out by elastic twisting of the coupler. The progressive stretching is performed, under temperature conditions providing a profile in the coupling region of the coupler having the property that the coupling strength for one of the principal polarization planes of the coupler remains substantially constant during said elastic twisting.

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: An active optical fibre star coupler having a length of amplifying optical fibre (1) optically connected at one end to a wavelength combining coupler (2) and at the other end to via a beam expanding element (3) to a set of output optical fibres.

Abstract: A method of making a single mode optical fibre directional coupler in which a pair of fibres (30,31) in side-by-side contact is subjected to a succession of drawing operations produced by traversing the fibres longitudinally through a flame (34) while stretching them between a pair of carriages (32,33) driven at slightly different speeds.