Polarization Multiplexing with the Kramers-Kronig Receiver

We present two schemes extending the Kramers-Kronig-receiver to polarization multiplexed transmission. One of the schemes relies on the Stokes receiver and allows for complex-valued polarization multiplexed transmission without using a local oscillator, and active polarization control at the receiver. It uses three photodiodes and requires three analog-to-digital converters (ADCs). The other scheme uses a local oscillator, and its implementation is suitable in all cases where the transmitter and the receiver operate at the same wavelength, so that the local oscillator signal can be extracted from the transmit laser. It uses only two photodiodes and two ADCs, and does not require optical hybrids. The performance of the first (Stokes-based) scheme is studied numerically, whereas that of the second scheme is studied both numerically and experimentally.