This International Standard applies to fibre optic wavelength switches. The term "fibre optic wavelength switch" can be used to describe a wide range of devices, assemblies and systems both active and passive. Therefore, it is necessary to elaborate on the scope and object of this standard. This specification is intended to cover those devices and assemblies which have the following attributes. – While the switch actuation means is by necessity active, the optical paths through the switch are passive. Thus, neither optical amplification nor opto-electronic conversion is encompassed. – The switch function is restricted to the routing of light rather than intentional power division plus routing. Thus, signal broadcast functions are not encompassed. – They have two or more ports for the transmission of optical power and have two or more states in which power may be routed or blocked between these ports. – The ports are optical fibres or optical fibre connectors. Wavelength switching normally involves separation of the individual wavelength streams of light which are re-routed and then recombined. Thus, wavelength switches may involve multiple optical junctions and multiple-stage switching layouts interior to the switch. However, the specifications relate to the optical performance from port to port of the overall assembly. System control and monitoring with their related electronics and software are not covered by this specification. The switch assembly may have optical means to facilitate such functionality (such as optical taps or wavelength monitoring means), but any related degradation in switch performance should be covered by the overall switch specifications. This specification deals with switches that incorporate passive optical paths, and, therefore, it may be assumed that the signal performance, other than through attenuation, is independent of the signal format. However, particularly in the case of wavelength switching, some technologies for switching and for wavelength discrimination may have an influence on the signals being carried on the channels. Some factors that must be considered are: spatial crosstalk, crosstalk in the wavelength domain, and polarization effects. This standard establishes uniform requirements for the following points: – fibre optic wavelength switch requirements; – quality assessment procedures.