应用等效折射率模型研究了光子晶体光纤(PCF)的传播特性。介绍了光子晶体光纤的等效折射率模型。通过求解标量波动方程得到了光子晶体光纤包层基空间填充模的模式折射率,利用阶跃光纤的理论来研究光子晶体光纤的导模特性。应用此模型对不同结构光子晶体光纤包层区的等效折射率与波长的关系进行了讨论。包层区等效折射率与芯子的折射率差随波长的增加而增大,并由此阐述了光子晶体光纤的单模特性。数值分析得到光子晶体光纤的基模的模式折射率,并由此研究了光子晶体光纤的波导色散与结构参量的关系。分析表明,光子晶体光纤的波导色散随空气孔孔距的变化符合Maxwell方程的比例性质。空气孔的相对孔径对波导色散有重要的影响。这些分析表明光子晶体光纤具有可以灵活设计其色散特性的潜在应用前景。

The propagation properties of photonic crystal fibers (PCF) are discussed with effective-index model. The effective-index model of photonic crystal fiber was introduced at first. By solving the scalar wave equation within cladding of PCF, the effective index of the cladding was calculated. Applying theory of standard fiber, we may calculate the propagation properties of PCF as a step-index fiber. With this model, the effective index of PCF cladding with different structure parameters was discussed. The refractive index difference of the core and cladding increases as the wavelength increases, and the endlessly single-mode behaviour was illuminated. The mode refractive index and the waveguide dispersion of the fundamental mode in PCF was calculated. It is shown that the relationship between waveguide dispersion and the air hole pitch is in accord with the scaling properties of Maxwell equations, the waveguide dispersion is also critically dependant on the size of the air hole. These analyses indicated that PCF is a promising component for enhanced control of dispersion in optical communication system.