Polarization-diversity Kramers-Kronig heterodyne receiver and method

An apparatus, comprising

• an input configured to receive a modulated optical data signal, the modulated optical data signal comprising components of a plurality of polarizations, the plurality of polarizations comprising at least a first polarization and a second polarization,
• a first optical detector coupled to the input to receive the modulated optical data signal, wherein the first optical detector is polarization-selective or polarization-sensitive to the first polarization and passes components of the modulated optical data signal comprising the second polarization, and wherein the first optical detector is configured to output a first electrical signal,
• a second optical detector coupled to the first optical detector to receive from the first optical detector the components of the modulated optical data signal comprising the second polarization, wherein the second optical detector is configured to output a second electrical signal, and
• a processor, the processor configured to
• apply a Kramers-Kronig, KK, process to the first electrical signal and to the second electrical signal, and
• output a data signal using the KK processed first and second electrical signals,
• wherein a combiner, like an optical coupler, is connected between the input and the first optical detector, the combiner configured to combine the modulated optical data signal with an unmodulated optical signal so that the unmodulated optical signal serves as a KK carrier for the first and second polarizations.