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报道了一种分析长周期光纤光栅(LPFG)透射谱谐振波长和衰减率随弯曲曲率变化的方法。利用耦合模理论和微扰近似推导了长周期光纤光栅透射谱随弯曲曲率变化的一般表达式,得到当弯曲曲率为2.56 m~(-1)时,长周期光纤光栅透射谱分裂,分裂峰的谐振波长和衰减率与弯曲曲率呈非线性变化,但分裂峰的间距与弯曲曲率呈线性变化。利用B-Ge共掺单模光纤写入的长周期光纤光栅证实了理论的正确性,且具有很好的重复性。
A method to analyze the change of resonant wavelength and attenuation rate of transmission spectrum of long period fiber grating (LPFG) with bending curvature was reported. The general expressions of the transmission spectra of the long period fiber gratings with curvature changes are deduced by coupling mode theory and perturbation approximation. The results show that when the bending curvature is 2.56 m ~ (-1), the transmission spectrum of the long period fiber gratings is split and the peak of splitting The resonance wavelength and attenuation rate vary nonlinearly with the bending curvature, but the spacing of the splitting peaks varies linearly with the bending curvature. Long-period fiber gratings written by B-Ge co-doped single-mode fibers confirm the correctness of the theory and have good repeatability.