Ultrafast two-bit all-optical analog-to-digital conversion based on femtosecond soliton sequence sampling.

Realization of two-bit all-optical analog-to-digital conversion for an analog signal sampled by a femtosecond soliton sequence is investigated. Two approaches are suggested. The first one is based on filtering the broadened soliton spectrum after evolution over half of the soliton period in a standard single-mode fiber. In the second approach, the pulse is temporally sampled at the specified times after propagating through one soliton period. The sampled soliton sequence must be amplified to achieve an initial peak power of between 0 and 75 kW for the first method and between 0 and 66 kW for the second method. The soliton pulse-width is 50 fs. Based on the resulted peak power, the "0" or "1" bit is generated with reference to the threshold values. Subsequently, the digital gray code is produced at the outputs. The effect of inaccuracy in filter frequency and fiber length are also studied in this paper. The first method is sensitive to variations in the filter frequency, whereas the second method is affected by the fiber length inaccuracy

Sliding mode control improvement by using model predictive, fuzzy logic, and integral augmented techniques for a quadrotor helicopter model

In this paper, a new control method is adopted based on merging multi-input Integral Sliding Mode Control with Boundary Layer (ISMC-BL), Model Predictive Control (MPC), and Fuzzy Logic Control (FLC). The aim of this merging is to take advantage of MPC ability to deals with constraints and to gain optimal solution. Moreover, FLC is considered in designing the sliding surface based on fuzzy rules and tracking error. This method is simulated on a nonlinear quadrotor helicopter model. The results have revealed that the proposed control approach, which is a multiinput Model Predictive Fuzzy Integral Sliding Mode Control with Boundary Layer (MPFISMC-BL), is a robust, stable, optimal, and intelligent control scheme. This finding could contribute to improve the control of similar systems

Disturbance rejection for a 2-DOF nonlinear helicopter model by using MIMO fuzzy sliding mode control with boundary layer

In this paper, one helicopter model with two degrees of freedom (2-DOF) is controlled by fuzzy sliding mode control with boundary layer (FSMC-BL) while exposed to disturbance. The model is a nonlinear and multi-input multi-output (MIMO) system that requires a MIMO, robust, stable, and nonlinear control to reject the disturbance. These requirements have been satisfied by SMC. In this paper, boundary layer removes the chattering phenomenon and fuzzy logic tunes the switching gains of SMC control law online. The simulation results which are achieved for step and sinusoidal disturbances applied to both pitch and yaw angles, are compared with those of PID control based on linear quadratic regulator algorithm (LQR-PID). Considerable improvement in control signal and yaw angle is observed by using FSMC-BL

Strategy on implementing genetic algorithm on FPGA for polarization control application

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Realization of microcontroller-based polarization control system with genetic algorithm

Realization of a PIC32 microcontroller-based polarization control system is described. Genetic algorithm is used for control purposes. The controller measures the signal intensity to estimate the genetic value. To reach optimum performance, the code is optimized by using the best genetic parameter to achieve the fastest execution time. This algorithm consumes low size of memory besides providing fast speed. The implementation of microcontroller allows for more economic polarization control solution

Propagation characteristics of femtosecond soliton and development of wavelength converter and analog-to-digital converter model

Research interests on femtosecond solitons have increased along with upgrading in ultrafast optics. Moreover, all-optical devices have been developed based on ultrashort solitons. Despite the wide attraction of femtosecond solitons, which lies in providing high resolution, high intensity, and high bandwidth, attempt in this realm is associated with more complexity and more problems due to manifestation of higher order linear and nonlinear effects. To get around these obstacles, many researches have been conducted during the last decades in both, reducing the destructive effects on pulse propagation and developing optimal devices based on ultrashort solitons. This dissertation investigates the potential of overlapping 50 femtosecond soliton in improving the propagation characteristics as a low power ultrafast pulse over standard single-mode fiber (SSMF). Pulse stream propagation is also explored. Moreover, realization of two all-optical devices, ultrafast wavelength conversion,and two-bit analog-to-digital conversion, are investigated for ultrashort solitons. First, improving the 50 femtosecond pulse propagation is realized by substituting input pulse with a reduced-order overlapping soliton pair. This approach decreases the pulse time delay compared to fundamental soliton and increases the pulse stability compared to reduced-order soliton. In the pulse stream, in addition to using overlapping soliton pair, perturbation is also applied to the fiber by step change in the second order dispersion to avoid pulses from collision. Second, survey on the realization of wavelength conversion, which is based on second-order 50 femtosecond dark solitons with hyperbolic secant pulse, is accomplished by introducing localized dispersion perturbation along the optical fiber. It is shown that the realization of 1×2 channel wavelength converter for femtosecond pulses is possible. Ultimately, realization of two-bit all-optical analog-to-digital conversion is explored for analog signal sampled by a 50 femtosecond soliton sequence. Two methods are exploited. The first one is based on filtering the broadened soliton spectrum after evolution over half of the soliton period. In the second one, pulse is temporally sampled at the specified times after propagating through one soliton period. The utilized methods in this research have fast response and relatively simple design in comparison to the existing solutions. Consequently, the main contributions include research for improving femtosecond pulse and pulse stream propagation over short fiber lengths, realization of all-optical wavelength conversion for dark soliton with hyperbolic secant pulse, and two-bit alloptical analog to digital conversion for femtosecond soliton