Abstract: The invention relates to a measuring arrangement for an optical spectrometer, in particular a photon density wave spectrometer, having a measuring chamber, which can be loaded with a sample to be measured, and a coupling-in/coupling-out device which is configured to receive excitation light from a light source and couple it into the sample to be measured in the measuring chamber and to receive measuring light formed in the sample to be measured on account of the excitation light which has been coupled in and to emit said measuring light to a detection device, wherein the coupling-in/coupling-out device has an optical switching device and a plurality of light guide elements which couple to the latter, have a respective optical waveguide and can be connected according to at least one selectable measuring configuration using the optical switching device in order to couple in the excitation light and receive the measuring light according to the at least one selectable measuring configuration, and wherein outputs