Study On Flattened-dispersion Characteristics Of Dual-mode In Photonic Crystal Fiber

Photonic crystal fiber is usually also called porous fiber ormacrostructure fiber for its cladding structural characteristics of airholes. The photonic crystal fiber with its periodic array of air holes inthe cladding structure has attracted the eyes of many scientists. Thestrict periodic array of air holes and the flexibility of the produce willmake the photonic crystal fiber has many novel properties whichother fiber have not, such as: High birefringence, Endless single modeproperty, Adjustable dispersion property, and High nonlinearcharacteristics；as well as the low loss, the large effective mode areacharacteristics, etc. In particular, there are more research on thedispersion, for example, a blue or red shift of the zero dispersion point,the high negative dispersion characteristic, dispersion compensationcharacteristic and dispersion-flattened characteristic, etc. While thecharacteristics of dispersion-flattened on photonic crystal fiber as apriority has been widely used in the conversion of wavelength, thedense wavelength division multiplexing and the generation ofultra-broad-band super continuum spectrum and etc. Various shapes(such as hexagonal, octagonal, honeycomb-shaped, etc.) and avariety of photonic crystal fiber core structure have also gradually been designed and produced, the scope of the research and the rangeof its application on the photonic crystal fiber are increasing.Although more and more research on the flattened dispersioncharacteristics of photonic crystal fiber has been made, the mainresearch focus on the fundamental model and a defected-core, whilehigh order modes and seven or more defected-cores, hardly anyresearch is made. This paper will concentrated on the photoniccrystal fiber with a variety of modes and seven air holes defect whichhave the dispersion-flattened character. Firstly, the multipole methodwill be used to obtain the dispersion equation, and then the dispersionequation will be programmed by the MATLAB language. Secondly,some data will be arbitrarily selected to satisfy multimode’spropagation, in other words, MATLAB language is used to calculatethe value of effective normalized frequency, if the value greater than2.405, using CUDOS software to calculate the relationship betweenthe effective refractive index and wavelength, and then importing thedata in the dispersion equation, respectively, under differentstructural parameters to simulate the fundamental mode and thesecond mode dispersion curve. Next, according to the analysis of thecurve, found the proper structural parameters, and ultimately havedesigned the dual mode flattened dispersion photonic crystal fiber ineach band.