256 Tbit/s/ch polarization-multiplexed DQPSK transmission over 300 km using time-domain optical Fourier transformation

We demonstrate a 2.56 Tbit/s/ch polarization-multiplexed single-carrier transmission over 300 km using subpicosecond DQPSK signals. We adopted an ultrafast time-domain optical Fourier transformation technique to reduce waveform distortions. For such an ultrashort optical pulse, depolarization components resulting from second-order polarization-mode dispersion (PMD) become a dominant factor as regards signal distortion because of the broad signal bandwidth. The influence of inter-polarization crosstalk induced by second-order PMD, is presented in detail.