Advances in fibre devices

Optical fibre devices are assemblies of fibre components, often incorporating special fibre designs, to form functional optical fibre circuits with a complexity which increases annually. Fibre circuits can be thought of as a discrete technology which can exceed the complexity of integrated optics and which has a number of important attributes. These are: low intrinsic losses, low interconnection losses, polarisation independence and relatively low manufacturing and assembly costs. However, it should be recognised that optical fibre devices are relatively large (ie long), they cannot easily be modulated, they have small electro-, acousto- and magneto-optic interactions, and a small third-order and a negligible second-order non-linearity. Notwithstanding these disadvantages, a number of successes have been achieved, notably four-port fused-taper couplers, photorefractive Bragg grating filters and the erbium-doped fibre amplifier (EDFA). It is the purpose of this review to provide a critical appraisal of current optical fibre device work and to examine future prospects for the technology in the light of a number of recent developments (eg new glasses). Fibre amplifiers will be covered elsewhere in the Conference