| The chaos generated by optoelectronic oscillator owns the advantages of flat power spectrums and big correlation dimensions, has been found wide applications in the chaos communication, fast random number generator, chaotic lidar and optical time domain reflectometry. The structure of optoelectronic oscillator has won more interest and become a research hotspot, recently. In this thesis, the route to chaos and the characteristics of chaos which is generated by an optoelectronic oscillator are studied theoretically. The following are the main works:1. We introduce the basic characters and history of chaos, and summarize its main applications in the security communication, fast random number generator, chaotic lidar and chaotic optical time domain reflectometry. The researches about the chaos generated by optoelectronic oscillator are presented.2. The system of optoelectronic oscillator is described. We introduce the global structure and each component of the optoelectronic oscillator, and establish numerical model of optoelectronic oscillator, and obtain the differential delayed equations. 3. The dynamic characters of optoelectronic oscillator are studied theoretically based on the differential delayed equations. Routes to chaos of optoelectronic oscillator at different offset phases are demonstrated. The states from stable state to chaos by increasing the feedback strength are studied when the offset phase is kept at-π/4、π/4and0, respectively. The output regularities of the optoelectronic oscillator are analyzed from the bifurcation diagrams and the largest Lyapunov exponent traces. Features of each state are studied from the time series, power spectrums and phase portraits. The result shows that the chaos can be obtained in optoelectronic oscillator, but the routes are not the same when the offset phase is different. The outputs of optoelectronic oscillator contain the states of periodic oscillations and "breather", and approach to chaos finally when the offset phase is kept at-π/4. The output of optoelectronic oscillator reach the chaos through higher-harmonic bifurcations when the offset phase is π/4, while its output become to chaos after a pulse state when the offset phase is0.4. The characters of chaos generated by optoelectronic oscillator are analyzed. By studying the auto-correlation function, the bandwidth defined by the80%of energy and the largest Lyapunov exponents of chaos, the influence of offset phase and feedback strength on the time delay signature, bandwidth and complexity are demonstrated, respectively. The theoretical results show that the time delay signature can be suppressed when the offset phase was set around0, and increase the feedback strength can further suppress even conceal the time-delay signature. The sign of correlation coefficient corresponding to the time delay position will change when the offset phase and the phase shift caused by the delay feedback change a value of π/2. The bandwidth of chaos increases with the increase of feedback strength. In the case of weak feedback strength, the offset phase close to0is good to reach a broadband chaos; and the influence of offset phase on bandwidth is not important with a strong feedback strength. The complexity of chaos increases with the increase of feedback strength. And an offset phase near0has a bad influence to the complexity of chaos, when the feedback strength with a small value. The offset phase is almost not a factor that influences the complexity of chaos when the feedback strength is strong. |
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