Singlemode and Multimode Taper Optical Fibre Devices: Modelling, Testing and Fabrication

The evanescent field intensity outside a fibre can be increased several orders of magnitude by tapering it. Several tapered optical fibre based evanescent field devices have been reported in the literature. Cambridge University, UK, reported work on miniature dye lasers using a tapered fibre in a loop arrangement; but more importantly, a tapered single mode fibre bent into a small loop. This latter tapered device was used as an imunoassay for cholera antitoxin immunoglobulins and was based on fluorescence spectroscopy. The Naval Research Laboratories, USA, have reported on a MM tapered fibre which is chemically tapered to a point and can be used as a fluorescence based biosensor.