光子晶体光纤的弯曲损耗振荡特性分析

综合运用弯曲光纤的等效直光纤模型、全矢量频域有限差分法及各向异性完全匹配层吸收边界,计算了两种类型(折射率引导型和带隙型)光子晶体光纤(PCF)的弯曲损耗.通过数值模拟弯曲损耗随弯曲半径的变化关系,证实了两种光子晶体光纤均具有弯曲损耗振荡特性.进而分析了两种光子晶体光纤弯曲损耗振荡的产生机理并给出了与损耗峰对应的包层模式.结果表明,振荡的产生源于基模与包层模式的耦合,其中,折射率引导型光子晶体光纤的弯曲损耗振荡机理类似于传统双包层光纤,带隙型光子晶体光纤弯曲损耗振荡的产生则是两种不同类型的包层模式共同作用的结果.

Analysis of Bending Loss Oscillations in Photonic Crystal Fibers

The bending losses in refractive index-guiding photonic crystal fiber (PCF) and photonic band-gap fiber are analyzed by using equivalent straight fiber approximation and finite difference frequency domain (FDFD) method with anisotropic perfectly matched layers (PML) boundary conditions. The bending loss oscillations in the two kinds of PCFs are observed by simulating the relationship between the bending loss and bending radius, and the origin of the loss oscillations was analyzed. The cladding modes corresponding to loss peaks are identified. Results show that the oscillations are caused by the coupling between the fundamental mode and the cladding modes. Moreover, the origin of oscillations in index-guiding PCF is similar to that of conventional double-clad fiber, while the oscillations in the photonic band-gap fiber are caused by two different kinds of cladding modes.