Modulator unit for modulating the polarization of an optical signal, comprising: a light source; a polarization component separator; a phase modulator; a reflector; wherein the light source is designed to output an optical signal and emit the latter as an input signal in the direction of the polarization component separator, wherein the optical signal contains a first polarization component with a first polarization direction and a second polarization component with a second polarization direction; wherein the polarization component separator is designed to separate the first polarization component from the second polarization component and transmit the first polarization component via a first optical section and the second polarization component via a second optical section; wherein the first optical section is assigned a first signal propagation time and the second optical section is assigned a second signal propagation time, the first signal propagation time differing from the second signal propagation time; wherein, as a result of the difference between the first signal propagation time and the second signal propagation time, the polarization component separator is designed to introduce a time offset between the first polarization component and the second polarization component and transmit the first polarization component and the second polarization component on a joint optical path to the phase modulator; wherein the phase modulator is designed to modulate a first phase of the first polarization component in the first polarization direction and transfer the modulated first polarization component to the reflector; wherein the reflector is designed to retroreflect both the first polarization component and the second polarization component in the direction of the phase modulator and in the process modify the respective polarization such that the first polarization component with the first polarization direction receives the second polarization direction and the second polarization component with the second polarization direction receives the first polarization direction; wherein the phase modulator is designed to modulate a second phase of the retroreflected second polarization component in the first polarization direction and transmit the retroreflected first polarization component and the retroreflected second polarization component to the polarization component separator; wherein the polarization component separator is designed to eliminate the time offset between the retroreflected first polarization component and the retroreflected second polarization component and output the retroreflected first polarization component and the retroreflected second polarization component without a time offset via a joint optical path; wherein the modulator unit is designed to output the optical signal modulated thus as polarization-modulated output signal. a light source; a polarization component separator; a phase modulator; a reflector; wherein the light source is designed to output an optical signal and emit the latter as an input signal in the direction of the polarization component separator, wherein the optical signal contains a first polarization component with a first polarization direction and a second polarization component with a second polarization direction; wherein the polarization component separator is designed to separate the first polarization component from the second polarization component and transmit the first polarization component via a first optical section and the second polarization component via a second optical section; wherein the first optical section is assigned a first signal propagation time and the second optical section is assigned a second signal propagation time, the first signal propagation time differing from the second signal propagation time; wherein, as a result of the difference between the first signal propagation time and the second signal propagation time, the polarization component separator is designed to introduce a time offset between the first polarization component and the second polarization component and transmit the first polarization component and the second polarization component on a joint optical path to the phase modulator; wherein the phase modulator is designed to modulate a first phase of the first polarization component in the first polarization direction and transfer the modulated first polarization component to the reflector; wherein the reflector is designed to retroreflect both the first polarization component and the second polarization component in the direction of the phase modulator and in the process modify the respective polarization such that the first polarization component with the first polarization direction receives the second polarization direction and the second polarization component with the second polarization direction receives the first polarization direction; wherein the phase modulator is designed to modulate a second phase of the retroreflected second polarization component in the first polarization direction and transmit the retroreflected first polarization component and the retroreflected second polarization component to the polarization component separator; wherein the polarization component separator is designed to eliminate the time offset between the retroreflected first polarization component and the retroreflected second polarization component and output the retroreflected first polarization component and the retroreflected second polarization component without a time offset via a joint optical path; wherein the modulator unit is designed to output the optical signal modulated thus as polarization-modulated output signal.