Research Of Dispersion And Nonlinearity In Microstructure Fiber

These research works of this dissertation are supported by National Basic Research Program of China (No.2003CB314900), the Key Grant Project of Chinese Ministry of Education (No.104046) and Co-Constructed Project of Beijing Education Committee (No.XK100130437).Microstructured fiber (MSF) has many unusual properties compared to conventional optical fiber, such as endless single mode propagation, flexible and controllable dispersion properties, controllable mode fields, high birefringence etc. Therefore MSF has already found important applications in optical communication, fiber sensing and many other fields. With respect to optical communication, MSF can be used for bandwidth expansion, dispersion compensation, pulse compression, short soliton transmission and generation of super-continuous spectrum etc. In this thesis, the theoretical and experimental research of dispersion and nonlinearity is discussed in detail, the main contents and innovations are listed as follows:1. Module BeamPROP in commercial software Rsoft is studied for simulation. Matlab is aided for design of the end face of MSF, dispersion and mode characteristics in the process of transmission are simulated by BPM, the results are dealed with to plot the dispersion and nonlinearity curves.2. The above method is used to design broadband dispersion compensation MSF in 1550nm wavelength range. The MSF structure is three-tier air hole with different diameters, the best structure is found to compensate ordinary single-mode fiber (G.652) more than 100 times with a bandwidth of 100 nm . Then, the relation between nonlinearity and fiber parameters is studied. Finaly, possible deviation of dispersion and nonlinear coefficient due to an error less than 3% in fiber production process is discussed.3. According to nonlinear Schrodinger equation, the transmission characteristics of picosecond pulse in MSF are simulated using the step-by-step Fourier algorithm, the nonlinearity and dispersion condition is found to realize generation of super-continuous spectrum.4. On the basis of simulation results of step-by-step Fourier algorithm, when picosecond pulse transmitted in dispersion-flattened MSF, self-phase modulation (SPM) is used to measure the nonlinear coefficient in 1550nm. By measuring the input peak power and the output spectrum, nonlinear coefficient of MSF can be calculated. This method is simple and accurate, the error between experimental result and the result supplied by the fiber producer is within 1%.5. An optimized algorithm is studied for FDTD method and its algorithm flowchart for fiber designing is given.