IEC 61755-3-10: 2016 defines certain dimensional limits of a 125 mm diameter single mode silica fibre optical interface and an alignment bore to meet specific requirements for non-angled fibre-to-fibre interconnection as defined in IEC 61755-2-1. The silica fibre materials specified in this document are suitable for use in categories C, U, E and O as defined in IEC 61753-1. Keywords: 125 mm diameter single mode silica fibre optical interface