Optical measuring system for determining polarization-optical properties of a sample, which comprises a polarization state generator (PSG) which is configured for preparing a measuring light which is propagating along an analysis beam path with a defined polarization state; a sample receptacle which is arranged downstream of the PSG in the analysis beam path and which is adapted for receiving the sample; a polarization state analyzer (PSA) which is arranged downstream of the sample receptacle in the analysis beam path; a detector which is arranged downstream of the PSA in the analysis beam path for detecting the measuring light, wherein the PSA and the detector are configured for capturing a polarization rotation αP(λeff) of the measuring light which is caused by the sample; and an evaluation and control unit for evaluating measuring signals from the detector and/or PSA and/or PSG, wherein a wavelength-spectrum of the measuring light contains at least a first wavelength λ1 and a second wavelength λ2, wherein the detector is configured for detecting measuring light with the first wavelength separated from measuring light with the second wavelength, and wherein the evaluation and control unit is configured for calculating a polarization rotation αP(λ0) of the measuring light which is caused by the sample at a standardized wavelength λ0 in dependency from (a) a first polarization rotation αP(λ1) at the first wavelength λ1, (b) a second polarization rotation αP(λ2) at the second wavelength λ2, (c) a first transmission T(λ1) at the first wavelength λ1, and (d) a second transmission T(λ2) at the second wavelength λ2.