Design And Research Of Few-mode Photonic Crystal Fibers And Mode Converter Of Mode Division Multiplex

In the past decades,the transmission capacity of wavelength division multiplexed system has met the Shannon limit.In order to explore avenues of further increasing data transmission capacity,the mode division multiplexing?MDM?techniques come into being.Using the higer order modes in the few mode fiber as independent signal channels,which can increase the system capacity and the spectral efficiency in multiples.In addition,mode converter based on coupled-mode theory is one of the key technology of MDM,which is a hot research issue in this field.The photonic crystal fiber has been attracting worldwide interest owing to its unique optical properties and design flexibility.The mode characters in few mode PCF and mode coupling are analyzed which provides a theoretical basis to the research.The specific efforts of this paper are listed as follows:Firstly,a single core two-mode PCF is designed for long distance and large capacity optical fiber transmission system.The PCF is in stable dual-mode operation at the wavelength of1.46-1.56?m.The effective refractive index difference is greater than10^-3,which can avoid the mode crosstalk.The dispersion coefficient of each mode in the C band was 2.138ps/?nm·km?and1.154ps/?nm·km?respectively.The dispersion slope values range from-0.012 to 0.322ps/?nm²·km?,which means dispersion-flattened in the wavelength range of communication.The mode area is106.72 m² and 155.34m² respectively,and the loss less than 10^-4d B/m.Transmission properties of the fiber can basically meet the G.652 and G.655 fiber standards,and it can be made by the existing mature technology.Secondly,a mode converter based on dual core PCF structure is proposed for the mode conversion in the MDM system,which realize the conversion of LP₀₁ and LP₁₁ mode with low loss.The conversion efficiency is 92.93%at a large bandwidth of 60nm.The structure model of division multiplexing system based on the designed practical few-mode PCF and mode converter is introduced.The related technical problems are discussed in this paper,the research based on PCF is conducive to enhance the performance and bandwidth of the next generation of transmission and access networks.