120 Gbit/s, polarization-multiplexed 10 Gsymbol/s, 64 QAM coherent transmission over 150 km using an optical voltage controlled oscillator

We report a polarization-multiplexed, 10 Gsymbol/s 64 QAM coherent transmission over 150 km using an optical voltage controlled oscillator (OVCO). The OVCO enables us to realize a low phase noise optical phase-locked loop (OPLL) due to its wideband operation independent of the frequency modulation (FM) bandwidth of an LD. As a result, 120 Gbit/s, 64 QAM data were successfully transmitted over 150 km with a power penalty as low as 1 dB.