Versatile coupling of a Plastic Optical Fibre bundle to an avalanche photodiode array

With the increasing use of optical fibre in both the telecommunications and home networking areas, the packaging and alignment of various optoelectronic devices has never been more critical. In particular coupling of Plastic Optical Fibre (POF) to detectors has become an important area of research. Most off-the-shelf POF has a core diameter of 980μm, while a typical photodiode may have an active area diameter of 50μm. Hence without some kind of physical alignment losses may become unmanageable. This paper describes efforts to couple Plastic Optical Fibres to an avalanche photodiode (APD) array. An imaging POF fibre-bundle is used to connect to the array in a low cost versatile manner. An array of up to ten fibres is used to form the bundle. Mechanical guide systems both on the substrate of the chip and on the package housing itself are used to align each individual fibre to a corresponding photodiode. The results from several focusing techniques are presented to overcome coupling losses encountered while focusing the beam from the POF onto the smaller detector active area. A multi fibre connector is used to connect other instruments at the opposite end of the fibre bundle. The primary application of this technology will enable the use of arrays of photon counting detectors in astronomy.