The invention relates to determining a polarization dependent property of an optical device under test, wherein a response signal is received from the device under test in response to an optical stimulus signal having an reference state of polarization, an output state of polarization of the response signal is determined, a reference information about the reference state of polarization is received, the reference state of polarization is determined on the base of the reference information and a predefined function describing the dependency of reference information versus the reference state of polarization, and the polarization dependent property is determined on the base of the reference state of polarization and the output state of polarization.