Abstract: An amplifier/filter combination including a fibre amplifier (4) and a fibre reflection/transmission filter (5) coupled to said amplifer. The fibre amplifier amplifies an input signal (1) in response to pump light (2) received from a laser. Preferably the fibre filter (5) is a chirped Bragg fibre filter which is arranged to filter out the unabsorbed portion of the pump light from the output amplified signal and which reflects the unabsorbed portion (7) of the pump light back to the amplifier (4) for re-absorption therein. The amplified signal (6) is transmitted by the filter (5) to a receiver.

Abstract: The optical fibre lattice signal processor comprises at least two coupling devices through which two optical fibres pass in a manner permitting optical coupling therebetween. The optical coupling devices are arranged in parallel with respect to each other and each fibre experiences a 180.degree. turn between the couplers. Recursive and non-recursive arrangements are provided for, together with equal and arbitrary delays.

Abstract: An optical device comprising a length of optical fibre of predetermined convex configuration supported by fibre mounting and/or attachment means, the convex outer part of the optical fibre having a portion thereof removed therefrom closely adjacent to or even just entering the core of the optical fibre to produce a substantially flat surface therealong on which a reflective diffraction grating of predetermined form is provided according to the function requirements of the device.

Abstract: Optical apparatus for determining for example by display on an oscilloscope the refractive index profile across an optical fibre including an ellipsoidal reflector and a scanning system for a laser beam directed towards one focus of the ellipsoidal reflector at which point the fibre to be examined is placed and including a detector which is relatively small in size situated at the other focus of the ellipsoidal reflector.

Abstract: A holographic data storage system for the storage and retrieval of data which includes in combination input means adapted to produce a number of coherent beams; wavefront matching means comprising at least one cylindrical lens for facilitating the discrimination of date; a storage medium adapted to store a number of data tracks, and capable of movement in a plane perpendicular to the plane of incidence; stepping means which is adapted to direct the number of beams produced by the input means on to the storage medium in a manner whereby a number of data tracks are recorded or retrieved, and read out means capable of controllable selective retrieval of date.

Abstract: This invention relates to an optical system for the production of a beam of light having a uniform intensity distribution. The optical system includes at least one Fresnel biprism for converting a beam of light having a non-uniform intensity distribution into a beam of light having a uniform intensity distribution.