Study On The Dispersive And Nonlinear Properties Of Microstructured Fibers

This work was supported by Natural Science Fund of Gansu Province (No. 3ZS062-B25-036), China and the Outstanding Young Teacher Training Plan of Lanzhou University of Technology, Lanzhou, China.Compared to the conventional optical fibers, microstructured fibers have many unusual properties. In this thesis, the numerical properties of the dispersion and nonlinearity of microstructured fibers are discussed in detail, the main contents and innovations are listed as follows:1. The dispersive and nonlinear properties of the microstructured fiber with hexagonally distributed air-holes in the cladding are numerically simulated. A microstructured fiber for broadband dispersion compensation with low nonlinearity was designed through separately adjusting the diameters of the inner three air-hole rings and the lattice pitch in the cladding. The proposed microstructured fiber has a large negative dispersion of-3235.8ps/nm/km at the wavelength of 1.55μm, which can compensate (to within 0.5% of the dispersion compensation ratio) the dispersion of 190 times length of standard single mode fiber over the entire 100nm wavelength range centered at 1.55μm. Furthermore, the proposed fiber also can retain the nonlinear coefficient lower than 5/W/km over this wide wavelength range.2. A microstructured fiber for broadband dispersion-compensating with low nonlinearity in a wide wavelength range centered at 1550nm is designed, the effects of the number of air-hole rings, the air-hole diameter and the lattice pitch on both dispersive and nonlinear properties are numerically described. The results indicate that the inner six air-hole rings have stronger impact on the dispersive and the nonlinear properties. By optimizing and adjusting the diameters of the inner 4th to 6th air-holes and the lattice pitch, the proposed microstructured fiber can compensate (to within %0.5) the dispersion of 190 times of its length of standard single mode transmission fiber over the entire 100nm band centered at 1550nm, while also can remain the nonlinear coefficient lower than 3/W/km over the wide wavelength range.3. A novel dual-core microstructured fiber based on pure silica for broadband dispersion compensation with low nonlinearity was proposed. The influence of the air-filing fraction in cladding and the distance between the inner and outer cores on the dispersion and nonlinear coefficient was numerically investigated. The simulation results show that by introducing the outer core by removing one air-hole ring in the cladding and by adjusting the distance between the inner and outer cores and the air-filing fraction, the mode coupling of the inner and outer cores can take place in a wide wavelength range, which could induce larger negative dispersion.4. The dispersive and nonlinear properties of modified microstructured fibers with different structural parameters are numerically simulated, the relationship of dispersion D, nonlinear coefficient y with the lattice structure is analyzed. The results show that the dispersive and nonlinear properties of the proposed fiber can be flexibly controlled by adjusting the structural parameters.5. A long-period grating in microstructured fiber was imprinted by mechanical pressure using flat broadband supercontinuum as light source and periodic metal wires on which tunable period can be produced, and relationship of the depth of pulse transmitted spectrum vs the pressure was investigated. The experimental results show that when the pressure varies between 20-60N, the linearity degree of the pressure-transmission peak attenuation curve is as much as 0.9953 and the sensitivity is 0.5dB/N.