Four-Dimensional 8-bit Modulation with KP4 Non-binary FEC for Short-Reach Coherent Optical Transmissions

C4-256 four-dimensional 8-bit modulation with non-binary FEC is firstly proposed and demonstrated for coherent optical transmissions, which outperforms its PM-16QAM counterpart by 0.7-dB for required OSNR at 10−8 post-FEC BER.