Dual-Polarization On-Line 256 and 512 QAM Digital Coherent Transmission

We demonstrate the first dual-polarization on-line 5 Gbaud, 256 and 512 QAM coherent transmissions using an FPGA-based transmitter and receiver. Error-free operation with 14 % overhead FEC was achieved for 256 QAM-160 km and 512 QAM-20 km transmissions.