This part of IEC 63267 defines the dimensional limits of an optical interface for reference connections necessary to meet specific requirements for fibre-to-fibre interconnection of non-angled and angled polished multimode reference connectors intended to be used for attenuation measurements in the field or factory.

Several grades of reference connections are defined in this document. The multimode reference connections are terminated to restricted IEC 60793‑2‑10 A1-OM2b to A1-OM5b fibre at the 850 nm band only. The geometrical dimensions and tolerances of the specified reference connections have been developed primarily to limit the variation in measured attenuation between multiple sets of two reference connectors, and therefore to limit the variation in measured attenuation between randomly chosen reference connectors when mated with connectors in the field or factory.