This part of IEC 61755 defines dimensional limits and material properties of a 2,5 mm and a 1,25 mm diameter cylindrical composite ferrule optical interface to meet specific requirements for PC fibre-to-fibre interconnection. The composite ferrule uses different materials in the end face contact zone and in the ferrule to sleeve contact zone. The specified materials for each zone are Zirconia (ZrO2) for the ferrule to sleeve contact zone and Cu-Ni-alloy for the end face contact zone. Ferrules made from the material specified in this document are suitable for use in categories C, U and O as defined in IEC 61753-1. NOTE If mated within the same family (cylindrical PC ferrule) the ferrules specified in this document are intended to have the same optical attenuation performance grade for connections with all ferrules described in IEC 61755-3 documents.