Polarization-multiplexed 1 Gsymbol/s, 128 QAM (14 Gbit/s) coherent optical transmission over 160 km using a 1.4 GHz Nyquist filter

Abstract
We have transmitted a polarization-multiplexed 1-Gsymbol/s, 128 QAM (14-Gbit/s) coherent optical signal over 160 km using a 1.4-GHz Nyquist filter. A heterodyne technique was used between a frequency-stabilized C2H2 laser and high-speed local oscillator.