Polarization multiplexing with the Kramers Kronig receiver

We present two schemes extending the KK-receiver so as to accommodate for 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. This is the first direct-detection-based scheme that allows polarization multiplexing. It uses three photo-diodes 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 transmitter laser. It uses only two photo-diodes 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.