448 Gbit/s, 32 Gbaud 128 QAM coherent transmission over 150 km with a potential spectral efficiency of 107 bit/s/Hz

We realized a single-carrier, polarization-multiplexed 32 Gbaud 128 QAM coherent transmission. Digital frequency-domain equalization enabled us to achieve waveform distortion compensation of a wideband data signal with high frequency resolution. Thus, we successfully increased the QAM multiplicity to 128 at 32 Gbaud, and transmitted 448 Gbit/s data over 150 km with a potential spectral efficiency of 10.7 bit/s/Hz. This is the highest multiplicity and spectral efficiency yet achieved in a coherent QAM transmission at a baud rate of as high as 32 Gbaud.