Analysis of the decrease in attenuation achieved by properly bending plastic optical fibres

When light propagates along a plastic optical fibre that bends sharply, an important amount of power can be lost through radiation around the bend. An analysis is made of how to reduce the radiation loss by shaping the bend into a suitable curve. To calculate the total radiation loss around the bend, a geometric approach to describing propagation in multimode optical fibres is used. Radiation loss only occurs at reflection or turning points, and is described by the power-transmission coefficient T. For step-index optical fibres, T depends mainly on the angle of incidence at the interface and on the core and cladding refractive indices and, to a lesser degree, on the light wavelength. Different bend shapes can cause very different radiation losses around the bend. The purpose of this paper is to show which curves give rise to the lowest attenuations and identify the reasons