This part of IEC 62074 applies to fibre optic wavelength division multiplexing (WDM) devices. These have all of the following general features: • they are passive, in that they contain no optoelectronic or other transducing elements; however they may use temperature control only to stabilize the device characteristics; they exclude any optical switching functions; • they have three or more ports for the entry and/or exit of optical power, and share optical power among these ports in a predetermined fashion depending on the wavelength; • the ports are optical fibres, or optical fibre connectors. This standard establishes uniform requirements for the following: • optical, mechanical and environmental properties.