IEC 62150-5:2017 specifies test and measurement procedures for the wavelength channel tuning time of tuneable transmitters. It applies to laser transmitters, and to the transmitter portion of transceivers. This procedure examines whether the device or module satisfies the appropriate performance specification. The method described in this document uses optical filters to transfer the transition of the output wavelength to the transition of the optical power. This is because the transient response of the output wavelength before stabilization at steady-state of the target wavelength channel is too fast to measure using a wavelength meter or an optical spectrum analyser. Reference optical filter sets are described in Annex A.