Abstract: A reflection hologram is recorded in a photosensitive film on a substrate held in a support by interference between an illuminating beam and its return from a back reflector. A scanning device moves the beam from a laser angularly about a fixed apparent beam source position which remains stationary relative to the film to give improved hologram formation with the back reflector spaced from the film.

Abstract: Lack of versatility and efficiency in optical multiplexing/demultiplexing is countered by progressing incident light along a wavelength selective holographic reflection filter which reflects different wavelengths at different positions along the filter. Light from a fibre optic input cable is directed by mirrors to make successive passes at the filter at respective different positions therealong and detectors receive the respectively reflected wavelengths. The filter preferably varies the reflected wavelength continuously and progressively as the incident light progresses along the filter.