基于耦合模理论和微扰近似,研究了长周期光纤光栅(LPFG)弯曲传感特性与弯曲曲率及光栅结构参数(光栅长度和栅格周期)之间的关系。当弯曲曲率增大到某一值时,一个透射峰分裂为两个,两个分裂峰的谐振波长与弯曲曲率的变化关系呈二次曲线关系,与栅格周期成反比变化,而与光栅长度基本无关。利用B-Ge共掺单模光纤制作的LPFG证实了理论的正确性,且具有很好的重复性。

A cetain value, a method to analyze bending sensing rules of long-period fiber grating (LPFG) according to bending curvature, grating length and grating period was reported, based on coupled-mode theory and perturbation approximation. When the bending curvature reaches a cetain value, the transmission spectra of the bended LPFG split. The two resonant wavelengths of the splitting peaks change conically with the bending curvature and inversely with grating period, but are indepentent on grating length. The LPFG written on the B-Ge co-doping single-mode fiber proves the above conclusion.