Back Propagation 1 Backpropagation 1 Cross-phase modulations 1 E-learning 1 Fiber nonlinearities 1 Gradient methods 1 Learning process 1 Light transmission 1 Nonlinear optics 1 Nonlinear waveform 1 Optimization 1 Performance 1 Quadrature amplitude modulation 1 Self phase modulation 1 Self-phase Span configuration 1 Stochastic systems 1 Wave length division multiplexed (WDM) 1 Waveform distortions 1 amplitude modulation 1 article 1 back propagation 1 calculation 1 learning 1 nonlinear system 1 polarization 1 stochastic model 1 waveform 1