Abstract: A modulator unit for modulating the phase of a polarization component of an optical signal contains a polarizing beam splitter and a phase shifter. The beam splitter splits an input signal into a first and a second polarization components having different polarization directions and sends the components in opposite directions via an optical ring containing the phase shifter. A polarization rotator is arranged in the optical ring, which changes the polarization direction of passing optical signals, so that the polarization components arriving at the phase shifter are polarized in the same direction. The phase shifter changes the polarization directions of the incoming optical signals such that they are polarized orthogonally to one another in the phase shifter. One polarization component is modulated. When the optical signals leave the phase shifter, their polarization direction is brought back to the original polarization direction.

Abstract: A modulator unit for modulating the polarization of an optical signal includes a light source, a polarization-dependent phase modulator, and a reflector. The light source outputs an optical signal and emits it as the input signal directed at the phase modulator. The optical signal contains a first and a second polarization components having a first and a second polarization directions, respectively. The phase modulator modulates a first phase of the first polarization component in the first polarization direction and passes on the modulated input signal to the reflector. The reflector retroreflects the received optical signal towards the phase modulator and changes its polarization by 90°. The phase modulator modulates a second phase of the second polarization component of the retroreflected optical signal in the first polarization direction. The modulator unit outputs the modulated optical signal as the polarization-modulated output signal.