Fig. 1. Schematic diagram of neuron

Fig. 2. Schematic diagram of neuron network

Fig. 3. Simulation setup of OSNR monitoring system

Fig. 4. Schematic diagram of proposed DNNs

Fig. 5. Test results of OSNR estimation by DNNs

Fig. 6. Averaged error of estimated OSNR versus number of DNN layers under different amount of training dataset

Fig. 7. MAE versus epoch during the 5-layers DNN training by 550 000 dataset

Fig. 8. Test results of OSNR estimation by the proposed DNN