Analysis of bent step-index optical fibres by the beam propagation method

The field distribution and loss in a single-mode bent optical fibre are analysed by the beam propagation method. The steady-state field at large propagation distances is compared with the field obtained by a perturbation theory. Transition loss and pure bend loss are also compared with other theoretical results. The reduction in bend loss is demonstrated by introducing an offset core and a trench section which is placed at the outer side of the bend. Differential-power-loss calculation reveals how the offset core and the trench reduce the bend loss