Fig. 8From: Research progress in optical neural networks: theory, applications and developmentsOptical spiking neural networks realized by WDM principle. a The structure of the first photonic neural network [58]. b Graphene spiking neuron [59]. c Bipolar integration-firing neuron with GST [60]. d The all-optical spiking neurosynaptic network structure formed based on the principle of WDM realized by PCM and MRR array [61]Back to article page