J. W. M. Menezes

All-Optical Half-Adder Using All-Optical XOR and AND Gates for Optical Generation of “Sum” and “Carry”

Abstract In this article, a numerical simulation study using the symmetric planar three-core non-linear directional coupler, operating with a short light pulse (2 ps), for the implementation of an all-optical half-adder is presented. The half-adder is the key building block for many digital processing functions such as shift register, binary counter, and serial parallel data converters. Optical couplers are an important component for application in optical fiber telecommunication systems and all integrated optical circuits because of very high switching speeds (as high as the femto-second range). In this numerical simulation, the symmetric planar three-core non-linear directional coupler presents a planar symmetrical structure with three cores in a parallel equidistant arrangement, three logical inputs (CP, A, and B), and two output logic functions (C and S). The CP(ΔΦ) input is a control pulse with a phase difference ΔΦ = Δθπ (0 ≤ Δθ ≤ 2) between inputs A and B (logical inputs of the half-adder) and one amplitude discriminator circuit. The half-adder uses two output logic functions of Sum(S) and Carry(C), which can be demonstrated by using XOR and AND gates, respectively. For the half-adder, the phase [ΔΦMIN, ΔΦMAX] intervals are studied, allowing the operation of the device as a half-adder. For the selected range of CP(ΔΦBETTER), the extinction ratio was studied, the compression factors for both Sum(S) and Carry(C) outputs of the symmetric planar three-core non-linear directional coupler.

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.

Study of the Performance of an All-Optical Half-Adder Based on Three-Core Non-Linear Directional Fiber Coupler Under Delayed and Instantaneous Non-Linear Kerr Responses

Abstract Recently, much attention has been given to the influence of the relaxation process of the non-linear response, because the usual assumption of instantaneous non-linear response fails for ultra-short pulses, and additional contributions coming from non-linear dispersion and delayed non-linearity have to be taken into account. This article presents a numerical analysis of the symmetric planar and asymmetric planar three-core non-linear directional fiber couplers operating with a soliton pulse, where effects of both delayed and instantaneous non-linear Kerr responses are analyzed for implementation of an all-optical half-adder. To implement this all-optical half-adder, eight configurations were analyzed for the non-linear directional fiber coupler, with two symmetric and six asymmetric configurations. The half-adder is the key building block for many digital processing functions, such as shift register, binary counter, and serial parallel data converters. The optical coupler is an important component for applications in optical-fiber telecommunication systems and all integrated optical circuit because of its very high switching speeds. In this numerical simulation, the symmetric/asymmetric planar presents a structure with three cores in a parallel equidistant arrangement, three logical inputs, and two output energy. To prove the effectiveness of the theoretical model for generation of the all-optical half-adder, the best phase to be applied to the control pulse was sought, and a study was done of the extinction ratio level as a function of the Δ > parameter, the normalized time duration, and the Sum and Carry outputs of the (symmetric planar/asymmetric planar) non-linear directional fiber coupler. In this article, the interest is in transmission characteristics, extinction ratio level, normalized time duration, and pulse evolution along the non-linear directional fiber coupler. To compare the performance of the all-optical half-adders, the figure of merit of the logic gates was used. All results were obtained numerically, considering a simple model for generation of an all-optical half-adder.

Hybrid Opto-Mechanical Current Sensor Based on a Mach-Zehnder Fiber Interferometer

In this paper, a new optical sensor based on a Mach-Zehnder interferometer, constructed with single mode optical fibers operating at 1.55 μm has been proposed and studied. The current sensing is obtained by mechanical perturbation applied to one of the single mode fiber, which constitutes the interferometer. This disturbance leads to an optical interference detected in the output of the interferometer and it is proportional to the magnitude of the current in the driver, measured with a reference sensor. The sensor has been tested with ac (60 Hz) up to 110 A. The obtained calibration curve presents a sensitivity between 0.8 and 1.54 mV/A. With a variation on the experimental arrangement, the sensor can be used in the monitoring of low and high amplitude currents. This new sensor can be efficiently used for monitoring the alternating electrical current in both small and large electric power suppliers and consumers.

High quality of logic gates from the return arm of a Sagnac fiber interferometer

Abstract In this paper, we analyze the characteristics of obtaining logic functions and logic gates in the reflected output of the Sagnac interferometer by unbalancing the interferometer through the effects of group velocity dispersion and self-phase modulation, mapped by the influence of the extinction ratio (XR) and also analyze the logic gates of better quality by proposing accuracy precision ratio (PR) defined. We studied the phase variation in the phase inserted to the input and we analyzed the related parameters of modulation. We investigated intrinsic features of reflection of the Sagnac interferometer and obtained the logic gates AND, OR, and XOR, and the logical functions ZERO, ONE, and . A specific situation happens when ρ = 0.3 and , where we find the logic gates AND, OR, and XOR. Of all results, the XOR logic gate was obtained in a greater phase variation interval. The XR had the highest contrast when ρ = 0.2 and |ɛ| = 0.028 W1/2. The proposed reconfigurable theoretical set-up gives a contribution to the design of optical networks by the analysis of the obtained logic gates and logic functions in an all-optical environment. The best quality logic gate is the AND gate presenting the |PRTOTAL| = 34.99 when .

Unbalance of the Sagnac interferometer through nonlinear asymmetry

ABSTRACT In this work, we studied the behavior of Sagnac interferometer powered by a CW signal and under the nonlinear effects of self-phase modulation, cross-phase modulation, and Raman, in two configurations (balanced and unbalanced) and five scenarios (by varying the value of the Raman fraction). In the balanced configuration, we observed that the presence of Raman effect in the loop changes the curves of transmissivity and reflectivity of the device, but only the components generated by the Raman effect (Stokes waves) are switched to the transmitted port. In the unbalanced configuration, we obtained an oscillating behavior as for transmissivity and reflectivity, which breaks the characteristic of nonlinear fiber mirror, thus enabling the transmission of the pumping wave for certain combinations of values of input power and Raman fraction.

Ultrashort Pulse Reflection through Nonlinear Fiber Bragg Gratings

We discuss numerical studies of reflection of an ultrashort pulse (1 ps) through 10 mm length nonlinear fiber Bragg gratings (NLFBG). The ultrashort pulse is a Gaussian function centered in the Bragg wavelength for low input intensities: lambda0 = 1550 nm. We used an inverse Fourier transform method never used before for nonlinear gratings to investigate the reflected time shapes. We determined how the nonlinear index affects the reflection responses for NLFBGs and subsequently its pulse reflection shapes. It was found that the nonlinear switching depends on nonlinear strength of grating.

Numerical analysis in triangular and planar three-core nonlinear optical fiber couplers (TNLDC) operating logical gates

In this paper, we investigate the switching process in triangular symmetric and planar symmetric three-core nonlinear fiber coupler (TNLDC) and we have numerically shown, via the coupled nonlinear Schrodinger equations (NLSEs), that logic gates AND, OR and NXOR can be constructed from a triangular TNLDC while the planar TNLDC produced logical gates AND, NAND, OR, and XOR. We consider two basic models. The first, one triangular symmetrical structure with three cores in an equilateral-triangle arrangement and using a control signal (CS) applied to the first core and the second model present a transverse symmetrical structure with three cores in a parallel equidistant arrangement (or planar symmetrical structure), however the position of the control signal (CS) is applied to the input of the first fiber (core 1). Looking at the transmission characteristics of the device, through the direct and cross channel, we did a study of the extinction ratio (Xratio) of these devices. In comparing the performance of both switches operating as logic gates we will use the figure-of-merit of the logic gates [FOMELG(dB)] defined as a function of the extinction ratio of the gate outputs.

Non-linear switching based on dual-core non-linear optical fiber couplers with XPM and Raman intrapulse applied to femtosecond pulse propagation

In this work, we investigated the optical switching process for three shapes of femtosecond pulses (soliton, Gaussian and super-Gaussian) propagating inside a symmetrical dual-core non-linear directional coupler by simulating their propagation via the coupled non-linear Schrödinger equations. In all simulations, we considered the dispersive effects of second and third order, besides the self-phase modulation and self-steepening non-linear effects. We studied three scenarios for each of the three pulse shapes under investigation. In the first scenario, we added only cross-phase modulation (XPM); in the second approach, we added only Raman scattering; in the third one, we combined both. The study was performed for distinct polarization modes and for different values of the Raman factor, with power range varying from 1 to 300 W. We noted that the XPM non-linear effect results in a decrease in the critical power threshold, whereas the Raman scattering causes an increase. For the first scenario (only XPM effect), the critical power threshold reduced from 113.72 to 104.69 W for the soliton pulse, from 111.49 to 100.77 W for the Gaussian and from 92.79 to 80.47 W for the Super-Gaussian pulse shape. For the second scenario (only Raman scattering), the critical power increased for a Raman factor varying from 1 to 10 fs, and the three pulse shapes reached thresholds above 150 W from a 5 fs factor, reaching more than 200 W for the super-Gaussian pulse as the Raman factor increased. For the third scenario (with both effects combined), we highlight that for a fixed XPM factor of 2, the critical power remained unchanged with the variation of the Raman factor. Hence, we observed that the Super-Gaussian pulse reached lower values for critical power when compared to the other pulse shapes.

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.