Fused taper single mode fibre couplers

This thesis contains a complete study of the symmetric fused taper single mode fibre coupler. A new fabrication technique for the coupler is developed and a stable and reliable coupler package is designed and implemented. Fundamental aspects of tapers and taper couplers are examined experimentally and the cladding mode nature of these structures is discovered. The cladding mode picture gives an elegant simplification of the description of used taper couplers in terms of the interference of the two lowest order cladding modes of the composite waveguide formed through the lateral fusion and tapering of the two fibres. Through this picture the relationship of the coupler's performance to the extent of tapering, the rate of tapering, the cross-sectional geometry and length of the coupling region, the refractive index of the external medium and the wavelength and polarisation state of the incoming light can be explicitly revealed. (DX84538)