All optical XOR logic gate formed by unsupervised optical neuron networks

We propose a design for an all-optical logic exclusive-OR (XOR) gate in terms of intensity-modulation or phase-modulation approaches. In this study, the unsupervised optical neuron networks (ONNs) are based on reservoir computing (RC) and the echo state networks (ESNs). Thanks to the optical interfering effect in the directional coupler, it provides a nonlinear function for the reservoir computing. By scanning the phase through the phase shifter in our optical neuron networks, we find the optimized results and demonstrate the relationship between the input and output signals. The simulated results match the truth logic table in XOR gate. We also demonstrate the bit error ratio (BER) of the all-optical logic XOR gate. The BER for intensity-modulation approach is 1.55% at 90 degree, and the phase-modulation approach is 1.78% at 91 degree. Thus, the simulated results also indicate that the optical neuron network has potential to achieve an optical integrated circuit. If this idea could be fabricated as an optical logic device, the processing rate in the ONN is in light frequency. It will help us to process the binary data sequence more efficiently.