Research On Design And Performance Of Polarization Splitter Based On Dual Core Photonic Crystal Fiber

With rapid development of the information society, the explosion of data in the internet has made transmission network entering the T bit era. the current communication network evolve to high bit, large capacity and ultra-broadband all-optical network, and it is urgent to improve the performance of key devices in optical communication network.Polarization splitters, which are based on birefringence, are an important device in all-optical network. The conventional polarization splitters rely on normal waveguides to obtain birefringence. Most of early waveguides had low birefringence coefficient, resulting in long splitters with small bandwidths and low extinction ratios.In recent years, photonic crystal fibers have attracted a considerable amount of interest due to their flexible structure and unique properties, such as endlessly single mode, high birefringence, high nonlinearity, and so on. The development of photonic crystal fibers have offered a new approach to design polarizations. This dissertation is focus on the theoretical investigation of the broadband polarization based on the dual-core photonic crystal fiber. The main research contents are as follows:1. With description of the coupling characteristics of dual-core photonic crystal fiber, two design about polarization splitter is proposed. Numerical results demonstrate that both introducing elliptical air hole and changing the mode field of the cores are benefit to improve the coupling length ratio.2. Compared with square and hexagonal D-PCF, octagonal D-PCF possess lower confinement loss. A novel polarization splitter based on octagonal dual-core PCF is proposed. The splitter exhibits an extinction ratio of 81.2 d B with low confinement loss of 0.2 d B/m at the wavelength of 1.55μm.3. Fluorine-doped cores and metal-filled central holes are demonstrated to increase the bandwidth of polarization splitter. A novel polarization splitter with bandwidth of 330 nm based on these two mechanisms of dual-core hybrid PCF is achieved.4. Through optimizing fiber configuration, a broadband polarization splitter based on graphene coated dual-core PCF is proposed. The fiber with 610 nm ultra-broadband bandwidth greatly simplifies the structures the PCF-based polarization splitter and make them practical.