Due to the ever-increasing digitization, the need for higher data transmission rates in fiber optic communication technology and the resulting demands on optical components are increasing at the same rate. A crucial point for wavelength division multiplexing (WDM) is the precise optical filtering of the individual wavelengths. This increases the demands on the optical diffraction gratings used in particular. For the exact determination of the respective diffraction angle and the resulting grating constant, MÖLLER-WEDEL OPTICAL GmbH offers the ideal solution with the GONIOMAT APLUS DGM.