Backpropagation 1 Channel wavelength 1 Coherent communication 1 Deep learning 1 Digital backpropagation Digital signal processing 1 E-learning 1 Non-linearity compensation 1 Optical fiber communication 1 Optical fibers 1 Optical-fiber communication 1 Stackings 1 Training time 1 Transmission link 1 Wavelength division multiplexing transmissions 1 deep learning 1 digital backpropagation 1 digital signal processing 1 nonlinearity compensation 1 optical fiber communication 1