We present an approach in which the differential evolution （DE） algorithm is used to address identification problems in chaotic systems with or without delay terms. Unlike existing considerations, the scheme is able to simultaneously extract （i） the commonly considered parameters, （ii） the delay, and （iii） the initial state. The main goal is to present and verify the robustness against the common white Guassian noise of the DE-based method. Results of the time-delay logistic system, the Mackey Glass system and the Lorenz system are also presented.
An approach to generate a flat optical comb with tunable comb spacing and adjustable comb number is proposed.In the proposed approach,a Mach-Zehnder modulator（MZM）,being biased to generate two carrier-suppressed first-order sidebands,is cascaded with a phase modulator.The two optical sidebands are then sent to the phase modulator to generate two identical,but frequency-shifted phase-modulated spectra.Thanks to the complementary nature of the two adjacent comb lines in the phase-modulated spectra,the overlapping of the two spectra would lead to the generation of a flat optical comb.Since only the phase modulation index or the microwave power is needed to be adjusted,the system is easy to be implemented with tunable comb spacing and adjustable comb number.Numerical simulations are performed,and the approach is verified by an experiment.
The dynamic behavior of an optical micro ring resonator （OMRR） with an amplitude modulator positioned in the micro ring is investigated quantitatively by adopting a recently introduced quantifier, the permutation entropy （PE）. The effects of modulation depth are focused on, and the roles of input power are considered. The two-dimensional （2D） maps of PE showing dependence on both modulation depth and input power are presented as well. PE values nearly increase with modulation depth. On the other hand, the optimal value of input power is achieved when the PE reaches its maximum. Thus, PE can successfully quantify the dynamics of modulated OMRR. Selecting the parameters in the region with high PE values would contribute to the complexity-enhanced OMRR-based chaotic communication systems.
