This part of IEC 61280 is applicable to the measurement of attenuation and optical return loss of installed optical fibre cable plant using single-mode fibre. This cable plant can include single-mode optical fibres, connectors, adapters, splices and other passive devices. The cabling may be installed in a variety of environments including residential, commercial, industrial and data centre premises, as well as outside plant environments. This standard may be applied to all single-mode fibre types including those designated by IEC 60793-2-50 as Class B fibres. The principles of this standard may be applied to cable plants containing branching devices (splitters) and at specific wavelength ranges in situations where passive wavelength selective components are deployed, such as WDMs, CWDM and DWDM devices. This standard is not intended to apply to cable plant that includes active devices such as fibre amplifiers or dynamic channel equalizers.