Proposed is a method of optical data transmission. The method comprises different steps. A first optical signal and a second optical signal are generated, such that the optical signals possess a same wavelength, respective phases, which are modulated in dependence on respective data values, and respective polarization states, which are essentially orthogonal to each other. A combined optical signal is generated, by combining the optical signals, such that the combined optical signal possesses a polarization state with a predetermined variation. The combined optical signal is transmitter over an optical transmission line and received. Two time-discrete sampled signals are generated, by sampling the received optical signal along two orthogonal polarization planes. Two filtered signals are generated, by filtering the time-discrete sampled signals in the time-discrete domain, using a function that is indicative of the respective predetermined variation. Finally, respective data values are derived from the filtered signals.