Fig. 1. Architecture of the proposed GRNN-NLE for QAM CO-OFDM system

Fig. 2. Simulation setup of CO-OFDM system

Fig. 3. Q factor versus σo in CO-OFDM system with (a) 16QAM and (b) 32QAM at different laser linewidths; (c) Q factor versus laser linewidth in the CO-OFDM system with different errors rg of objective function

Fig. 4. (a) Q factor versus laser linewidth using W/O-NLE, BPNN-NLE and GRNN-NLE; (b) training running time of BPNN-NLE and GRNN-NLE versus laser linewidth

Fig. 5. For the proposed CO-OFDM system, 32QAM constellation diagrams at the receiver after using GRNN-NLE (blue) and without nonlinear equalizer (red). (a) Laser linewidth ν=0.3 MHz; (b) ν=0.7 MHz