This part of 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 face contact 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 material specified in this document are suitable for use in categories C, U and O as defined in 61753-1.