Optimization of the coupling between a tapered fibre and a p-i-n photodiode

With increasing information flow, direct illumination of the photodiode intrinsic layer from the end of a fibre becomes a necessity. The active area size of the photodiode is much smaller than the spot size in the fibre. This paper proposes an optimized scheme for direct coupling between the fibre and the device. Different fibre extremities are investigated. It is shown that optical coupling could be optimized with an acid-etched taper ended by a lens of 13 mu m diameter or by a pulled and melted fibre with certain conditions of profiles.