H.H.B. Rocha

A performance study of an all-optical logic gate based in PAM-ASK

In this paper a numerical study of an all-optical logical gate based in a symmetric nonlinear directional coupler (NLDC) operating with two ultrashort fundamental soliton pulses of 2ps, modulated by PAM-ASK with binary amplitude modulation to represent the logical level 1 and 0, is presented. The performance of a symmetric dual core NLDC performing two-input logical functions is examined. Initially, we evaluate the effect resulting from an increment in the PAM coding parameter offset (ϵ), considering the anomalous Group Velocity Dispersion (GVD), nonlinear Self Phase Modulation (SPM) in a lossless configuration. We can conclude that is possible to get logical operations for the cores 1 or 2 since a phase control exists which is applied to the input pulse in fiber 1.

Optical Logic Gates Using Nonlinear Directional Coupler under Pulse Position Modulation

The implementation of optical logic gates in nonlinear fiber directional coupler is investigated numerically in soliton regime. The study shows that with a proper phase control it is possible to accomplish logical operations.

Signal coupling in nonlinear hybrid optical structures: A numerical approach

The numerical study of intensity-dependent picosecond solitonic pulse coupling in nonlinear fiber grating couplers, configured with in-phase or out-of-phase uniform Bragg gratings, is reported in the present work. The time domain non-linear coupled-mode equations that model the coupling dynamics in the devices under investigation are solved numerically by the choice of a fourth-order modified predictor-corrector method. The switching performance of the devices have been investigated as a function of the input power. Characteristically, the coupling effect is dependent on the operational power level, geometry, and, in particular, the mismatching between the adjacent gratings. In the linear regime, the numerical results indicate that the relative shift of the gratings can strongly modify the reflectivity of the optical modes, impacting on the extraction efficiency. As the intensity of the input pulses increases, the hybrid character of the devices vanishes, being the coupling results very similar, independently of the proposed arrangement.