Fig. 1. Experimental setup of parametric process-based ONN. DCF, dispersion compensation fiber; HNLF, highly nonlinear fiber; MLL, mode-locked laser; OSA, optical spectrum analyzer; PC, polarization controller; PD, photodetector.

Fig. 2. Simulation coding block diagram. Self-implemented simulation functions: SMF_simu( ), HNLF_simu( ), and DCF_simu( ).

Fig. 3. (a) Simulated data sample (flattened, “1”) with MNIST-digit database before nonlinear interaction in HNLF (red, frequency domain) and after HNLF (blue, time domain); (b) tendency of accuracy in relation of input power decay.

Fig. 4. (a) Encoded optical spectrum with MNIST-digit database before and after nonlinear interaction in HNLF; (b) confusion matrices with and without nonlinearity, 1200 samples; (c) confusion matrices with and without nonlinearity, 6000 samples.

Fig. 5. (a) Confusion matrices with and without nonlinearity, 1200 samples; (b) linear discriminant analysis with and without nonlinearity, 1200 samples.