An optical frequency domain reflectometry (OFDR) system, the system comprising: - an optical radiation source capable of emitting optical radiation within a certain wavelength band, the radiation source being optically connected to a first coupling point arranged for splitting the radiation into two parts, - a reference path, the reference path being optically connected to the first coupling point, - a measurement path, the measurement path being optically connected to the first coupling point, the measurement path further comprising an optical circulator, the circulator being optically connected to a measurement branch arranged for measurements based on reflected radiation, - wherein said reference path and said measurement path are optically coupled in a second coupling point, - an optical detection unit capable of obtaining a signal from the combined optical radiation from the reference path and the measurement path via the second coupling point, - wherein the measurement path comprises a polarization dependent optical path length shifter (PDOPS, PDFS, 10), the shifter having the function of inducing, or creating, a first polarization and a second polarization for the radiation in the measurement path, said first polarization being different from said second polarization, and characterized in that - the shifter further having the function that the optical path length is different for the first polarization in the measurement path relative to the second polarization in the measurement path, the measurement branch comprises an optical fiber arranged for providing reflections for OFDR along a sensing length (l s) of the optical fiber, and wherein the polarization dependent optical path length shifter (PDOPS) is further arranged so that the optical path length difference (Δ PDOS) between the first polarization and the second polarization in the reflection spectrum is chosen so as to avoid overlap in the reflection spectrum between the first polarization and the second polarization. - an optical radiation source capable of emitting optical radiation within a certain wavelength band, the radiation source being optically connected to a first coupling point arranged for splitting the radiation into two parts, - a reference path, the reference path being optically connected to the first coupling point, - a measurement path, the measurement path being optically connected to the first coupling point, the measurement path further comprising an optical circulator, the circulator being optically connected to a measurement branch arranged for measurements based on reflected radiation, - wherein said reference path and said measurement path are optically coupled in a second coupling point, - an optical detection unit capable of obtaining a signal from the combined optical radiation from the reference path and the measurement path via the second coupling point, - wherein the measurement path comprises a polarization dependent optical path length shifter (PDOPS, PDFS, 10), the shifter having the function of inducing, or creating, a first polarization and a second polarization for the radiation in the measurement path, said first polarization being different from said second polarization, and - the shifter further having the function that the optical path length is different for the first polarization in the measurement path relative to the second polarization in the measurement path, the measurement branch comprises an optical fiber arranged for providing reflections for OFDR along a sensing length (l s) of the optical fiber, and