The laboratory is responsible for the realization and dissemination of the SI unit of length "meter".
The meter is defined by the length of the path travelled by light in vacuum during a time interval of 1/299 792 458 of a second. The unit of length is thus linked up with the unit of time via the velocity of light.
The laboratory maintains different laser standards at different wavelengths: He-Ne/I2 at 633 nm, Nd:YAG/I2 at 532/1064 nm, optical comb in the visible and near infrared spectral range.
The laboratory issues calibration certificates for laser wavelength standards by comparing the frequency of the standards in controlled conditions and reporting in the certificate the absolute frequency and laser wavelength in vacuum. It’s up to the client laboratory to estimate the wavelength when used in different operating conditions.