The New Fiber-optic Frequency Domain Chaos Theory And Methods

Chaos is a unique behavior in the nonlinear dynamical system, and for the initial state it is extremely sensitive and seemingly random. So, the research about the chaos found wide potential application prospects in chaos-based secure communications. In the optical field, the chaos can be produced by controlling optical bistable system, which provides the simple and effective means for chaos research. But the traditional optical chaotic methods were mainly concentrated in controlling the intensity and polarization of fixed-wavelength laser. To a great extent, it largely hinders the generation and control of the complex chaos. Realization of optical bistable chaos in the frequency domain using the tunable laser can develop research and application of complex chaos from a new perspective.In this thesis, the principle and methods of realizing the chaos in frequency domain using the tunable laser is studied deeply. The novel system of all-fiber chaos in frequency domain is proposed firstly. And for the different types of nonlinear intensity modulator, mathematical and physical model of chaos in frequency domain is established, which are fiber Bragg grating, fiber Mach-Zehnder interferometer, fiber Michelson interferometer and fiber F-P interferometer. On the basis of the theoretical analysis, the computer software simulations are done to determine the system parameters. In the experiment, the tunable fiber laser is utilized as light source. The fiber negative components are used to be the intensity modulation unites. The feedback unites are composed of opto-electronic detecting and amplifying circuits. Based on the introduction of different feedback time delay, the chaos oscillation in frequency domain is realized through using the different optical devices. So the theory and model of fiber chaos in frequency domain is validated.The experiment phenomenon of the fiber chaos in frequency domain is analyzed systematically. The experiment results show that a new complex chaos generator whose nonlinearity induced by wavelength can be realized when we apply the long delay feedback in optical bistable and multistable system. The experimental setup is flexible and simple; the nonlinearity can be controlled accurately through wavelength. Chaos in frequency domain is a high dimensions chaos, its oscillation is complex and the system is all fiber to easily compact with other fiber components. Based on these advantages, a high confidential communication project is established by analysis and discussion for application of chaos device in secure communication. So for realizing the secure communication application, the foundation is laid.