Research On Dispersion Properties Of Several Dispersion-compensating Photonic Crystal Fibers

Photonic crystal has been proposed in the late 1980s, it is a kind of new material which guides light by a photonic bandgap effect and artificial microstructure which has a periodic arrangement of materials with various dielectric constants in space. Moreover, Photonic Crystal Fiber (PCF), often composed of single medium, is a new type of fiber that the structure of photonic crystal has been introduced and a kind of 2D defect photonic crystal.Photonic Crystal Fiber has been a subject of intensive research in communication field due to its excellent optical properties. During the past few years, due to the need of dispersion-compensating technology in the WDM optical communication system, the research of the dispersion-compensating photonic crystal fiber has been speeded.In this paper, the dispersion-compensating photonic crystal fiber was investigated, and three structures were proposed. The negative dispersion properties were analyzed using the full vector finite-difference frequency domain method (FDFD). And the influence of the structure parameters (the air-hole pitch and air-hole diameter) on the negative dispersion was discussed in detail. The results indicated that the three structures had the broadband negative dispersion properties at 1.55μm of the optical communication window with the appropriate structural parameters. These fibers can be applied for broadband dispersion compensation in wavelength-division multiplexing optical fiber communication system.The main contents of this paper include:1. The general introduction of photonic crystal fiber, especially the development of dispersion-compensating fiber was summarized.2. The first kind of PCF our proposed with dual-core and composite hexangular lattice, which the cladding is composed of two different air holes and the inner core is formed with high effective index doped material and the fourth ring of air holes in the cladding is omitted, was studied. The negative dispersion properties of the structure were analyzed in detail, and the broadband negative dispersion with full width at half maximum exceeding 200 nm was realized at 1.55μm wavelength by optimizing structural parameters.3. The second kind of PCF our proposed with dual-core and composite square lattice, which is similar to the first proposed PCF and the difference is the arranged air holes of square lattice, was introduced. The negative dispersion properties were analyzed, and the broadband negative dispersion with full width at half maximum exceeding 200 nm at 1.55μm was also realized at 1.55μm wavelength.4. The last kind of modified PCF our proposed with dual-core and composite square lattice, which the dual-core realized by not the doped inner core but the size of air holes, was introduced. The broadband negative dispersion with full width at half maximum exceeding 300 nm which is larger than the former two fibers was obtained.5. The research findings of the three proposed fibers were summarized, and the research work in future is looked forward to.