J.H. García-López

Synchronization of coupled bistable chaotic systems: experimental study

We carried out an experimental study of the synchronization of two unidirectionally coupled Rössler-like electronic circuits with two coexisting chaotic attractors. Different stages of synchronization are identified on the route from asynchronous motion to complete synchronization, as the coupling parameter is increased: intermittent asynchronous jumps between coexisting attractors; intermittent anticipating phase synchronization; and generalized synchronization in the form of subharmonic entrainment terminated by complete synchronization. All these regimes are analysed with time-series, power spectra and phase-space plots of the drive and response oscillators. The experimental study implicitly confirms the results of numerical simulations.

Novel communication scheme based on chaotic Rössler circuits

We present a novel synchronization scheme for secure communication with two chaotic unidirectionally coupled Rossler circuits. The circuits are synchronized via one of the variables, while a signal is transmitted through another variable. We show that this scheme allows more stable communications. The system dynamics is studied numerically and experimentally in a wide range of a control parameter. The possibility of secure communications with an audio signal is demonstrated.

SYNCHRONIZATION OF MULTISTABLE SYSTEMS

We present the detailed study of synchronization of two unidirectionally coupled identical systems with coexisting chaotic attractors and analyze system dynamics observed on the route from asynchronous behavior to complete synchronization when the coupling strength is increased. We distinguish three stages of synchronization depending on the coupling strength which can be conventionally divided into three intervals. A relatively weak coupling induces asynchronous intermittent jumps between coexisting attractors and anticipating phase synchronization within windows where the systems stay in similar attractors; an intermediate coupling creates combined attractors that give rise to generalized synchronization in the form of subharmonic frequency entrainment; and a strong coupling results in complete synchronization. The results of numerical simulations are in good agreement with experiments carried out with piecewise-linear Rossler-like electronic circuits.

Secure Computer Communication Based on Chaotic Rössler Oscillators

We describe a communication scheme based on chaotic Rossler oscillators for transmission of secure messages via computers. The computers are synchronized through one of the channels via one of the variables of the Rossler sys- tem, while an information signal is transmitted through another channel by adding the message to another system variable. This scheme provides more stable communication because the information signal does not enter to the receiver and hence does not cause an error in synchronization. The method is tested with different types of information signals: audio, text, and image.

Experimental Implementation of a Biometric Laser Synaptic Sensor

We fabricate a biometric laser fiber synaptic sensor to transmit information from one neuron cell to the other by an optical way. The optical synapse is constructed on the base of an erbium-doped fiber laser, whose pumped diode current is driven by a pre-synaptic FitzHugh–Nagumo electronic neuron, and the laser output controls a post-synaptic FitzHugh–Nagumo electronic neuron. The implemented laser synapse displays very rich dynamics, including fixed points, periodic orbits with different frequency-locking ratios and chaos. These regimes can be beneficial for efficient biorobotics, where behavioral flexibility subserved by synaptic connectivity is a challenge.

Family of Bistable Attractors Contained in an Unstable Dissipative Switching System Associated to a SNLF

This work presents a multiscroll generator system, which addresses the issue by the implementation of 9-level saturated nonlinear function, SNLF, being modified with a new control parameter that acts as a bifurcation parameter. By means of the modification of the newly introduced parameter, it is possible to control the number of scrolls to generate. The proposed system has richer dynamics than the original, not only presenting the generation of a global attractor; it is capable of generating monostable and bistable multiscrolls. The study of the basin of attraction for the natural attractor generation (9-scroll SNLF) shows the restrictions in the initial conditions space where the system is capable of presenting dynamical responses, limiting its possible electronic implementations.

Control of Attractor Preference by Low-Pass Filtered Noise in a Multistable Fiber Laser

Abstract A diode-pumped erbium-doped fiber laser with pump modulation shows a large dynamic behavior including the coexistence of multiple attractors. In this work it is demonstrated numerically and experimentally that a low-pass noise filtering can control the probability for the appearance of a particular state. The results of numerical simulations with the use of a three-level laser model display good agreement with experimental results. We construct three-dimensional bifurcation diagrams of the probability using the noise amplitude and cutting frequency as control parameters. Finally, it is found the existence of one noise amplitude that cause one periodic orbit to appears more frequently compared to different noise amplitudes.