Nanlyse The Transmission Characteristics Of Novel Dual-core Photonic Crystal Fiber

The traditional dual-core optical fibers have shortcomings of production process trivaland higher requirements to technology, but the dual-core photonic crystal fibers (PCF) are notonly have relatively simple production process, and also have good coupling characteristics.They are widely used in filters, couplers, polarization beam splitters, optical switches, sensors,the development of the multiplexers, etc, so they have important application values.In this paper, three different structures of dual-core PCF have been designed, the fullvector finite element method (FEM), the beam propagating method (BPM) and coupled-modetheory are employed to investigate the coupling properties and temperature sensing propertiesof the designed dual-core PCFs, meanwhile, the relevant application of the novel dual-corePCFs in polarizing splitter, coupler and sensor have also been researched. The major contentsare as follows:First, a high-polarization dual-core PCF with mixing air holes is designed, the full-vectorFEM and coupled-mode theory are used to investigate the birefringence, coupling length,dispersion characteristics, and its applications in miniature polarization splitter and couplerare discussed. The numerical investigations demonstrate that by changing the structuralparameters of the fiber, the birefringence is up to1.48102at1.55μm, the couplinglengths are79μm and94μm for x-polarized and y-polarized modes, the fiber has twozero dispersion points, and the dispersion is flat at the ultra-wide waveband scope from0.7μm to1.7μm. The length of the fiber is1032μm or470μm for fabricating a coupler or apolarization splitter, and the extinction ratio of polarization splitter is70.3dB.Second, a new kind of dual-core PCF polarization splitter based on tellurite glass is putforward, the full-vector FEM, coupled-mode theory and the BPM are emplyed to investigatethe characteristics of the polarizing splitter, meanwhile, the same structural parameters ofquartz glass dual-core PCF polarization splitter is applied to compare. Numericalinvestigations demonstrate that the polarization splitter we designed has higher extinctionratio and the coupling loss is very low, the two polarized lights are splitted entirely along with441μm, at the wavelength of1.55μm, the extinction ratios in x and y polarizationdirection are50.1dB and53.6dB, and the bandwiths are34nm and36nm when theextinction ratio is less than20dB, respectively, the coupling loss is only0.0009dB.Third, an octagonal PCF with dual-core is proposed, analyzed its temperature propertieswith filled liquid. The full-vector FEM and coupled-mode theory are used to investigate theinfluence of temperature on effective refractive index, coupling length, confinement loss andmode field distribution, the confinement loss of the same structural parameters of hexagonPCF is calculated and analyzed at the wavelength of1.55μm. Theoretical calculations showthat mode field distribution is impacted by temperature and wavelength, effective refractive index and the coupling length decrease with the increasing of temperature, confinement lossincreases as temperature increasing. Fixed structure, the conditions of long wavelengths andsmall ellipse rate have a better sensitive characteristic to temperature; nonfixed structure, thelarger of the duty ratio has a higher sensitive characteristic to temperature. The confinementloss of photonic crystal fiber with octagonal structure greatly reduces compared withhexagonal structure at1.55μm and the same temperature.