All-optical logic gates based on XPM effect under the PAM-ASK modulation in a symmetric dual NLDC

Abstract

We investigate the possibility of achieving all-optical logical gates based in a symmetric double non-linear directional coupler (NLDC) working with pulses of 2 ps coded for the pulse amplitude modulation-amplitude shift keying (PAM-ASK), in a digital keying. The effects of group velocity dispersion, nonlinear self phase modulation and cross phase modulation (XPM) are taken into account in a lossless theoretical setup scheme. We analyze the amplitude and shape of the output pulses as a function of the modulation factor \((|\varepsilon |)\) to show that an OR gate can be readily realizable. Further, we also implement an optical sign phase shift in one of the NLDC input channels after the PAM-ASK modulator. We identify parameter regions on which the logical operations NAND, OR and XOR can be performed with the respective re-configurable scheme set by PAM-ASK modulation technique under the XPM effect.