Tapering of single-mode optical fibres

In the paper, the local-mode evolution in a single-mode optical fibre is examined during tapering. Observed mode coupling effects are explained using the mode coupling theory between the fibre core and cladding. Alternatively, the taper is viewed as a multimode waveguide and local-mode interference of relevant modes explains the power transfer between the core and cladding. Practical applications of such tapers as all-fibre devices are highlighted.