Fig. 1. Fiber transmission model and LDBP structure

Fig. 2. DSP structure of coherent receiver for dispersion and fiber nonlinear impairment compensation based on LDBP algorithm

Fig. 3. Parameter optimization of received signal sequence

Fig. 4. Single channel 12.5-GBaud 16QAM coherent optical transmission system

Fig. 5. SNR versus different launch power after 1 200 km transmission distance

Fig. 6. SNR versus different transmission distance at launch power of 1 dBm