IEC 62074-1:2014(E) 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. This second edition cancels and replaces the first edition, published in 2009, and constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition: - substantial updating to the definitions; - the addition of informative Annexes C to G, giving examples of technical information concerning WDM devices. Keywords: fibre optic wavelength division multiplexing, WDM, requirements for optical, mechanical and environmental properties