Jin Long, Wang Zhi, Fang Qiang, Liu Yange, Liu Bo, Kai Guiyun, Dong Xiaoyi
Opt Express. 2007 Nov 12;15(23):15555-65. doi: 10.1364/oe.15.015555.
In this paper, we investigate the spectral characteristics and bend response of fiber Bragg gratings (FBGs) in all-solid photonic bandgap fibers (PBGFs). We inscribe FBGs within the secondary bandgap by ultraviolet (UV) side illumination and observe the couplings to backward core mode, guided LP(01) and LP(11) supermodes and radiative LP(02) supermodes. The mechanisms of these resonant couplings in the FBG are described in detail. We demonstrate that only those supermodes with certain phase relationships and symmetric mode field profiles are responsible for the supermode resonances. When the fiber grating is bent, the guided supermode resonances become chirped as a result of the strain gradient over the fiber cross section. Meanwhile, the core resonance is enhanced, due to more energy of the core mode distributed in the cladding rods. The bend response is direction dependant owing to the nonuniform UV-induced average index raises and index modulation over the high-index rod lattice. .
在本文中，我们研究了全固态光子带隙光纤（PBGF）中光纤布拉格光栅（FBG）的光谱特性和弯曲响应。我们通过紫外（UV）侧面照射在次带隙内写入FBG，并观察到与反向纤芯模式、导模LP(01)和LP(11)超模以及辐射LP(02)超模的耦合。详细描述了FBG中这些共振耦合的机制。我们证明，只有那些具有特定相位关系和对称模场分布的超模才会导致超模共振。当光纤光栅弯曲时，由于光纤横截面上的应变梯度，导模超模共振会发生啁啾。同时，由于纤芯模式的更多能量分布在包层棒中，纤芯共振会增强。由于紫外诱导的平均折射率升高和高折射率棒状晶格上的折射率调制不均匀，弯曲响应取决于方向。
