利用长周期光纤光栅(LPFG)的双峰谐振效应，结合LPFG 传感器工作于近相位匹配转折点(PMTP)附近的高灵敏度，提出了一种新型的长周期光纤光栅应变传感器的设计方法。利用LPFG 相位匹配条件，分析了长周期光纤光栅近PMTP 附近的双峰谐振特性、应变传感特性，发现双峰波长间距对微小应变具有很高的响应度和线性度。进一步讨论了光栅结构参数和包层直径对双峰LPFG 应变灵敏度的影响，发现光栅周期对该传感器的应变灵敏度、线性度和应变测量范围具有很大的影响；光栅长度对谐振峰高度和宽度有较大影响，直接关系到传感器寻峰精度；通过增大包层直径，可以进一步增大应变灵敏度。结果表明，通过选取适合的光栅结构参量和包层半径，该传感器应变灵敏度可比一般长周期光纤光栅应变传感器的应变灵敏度提高2 个数量级。这为设计高应变灵敏度双峰谐振LP?FG 应变传感器提供了结构优化的理论支持。

A novel long- period fiber grating (LPFG) strain sensor is presented, which is based on dual- peak resonance combined with high sensitivity of LPFG nearby phase-matching turning point (PMTP). The dual-peak resonant characteristics near PMTP and strain sensing properties of LPFG are analyzed firstly by phase-matching condition of LPFG. It is found that dual-peak wavelength spacing has high response and linearity on small strain. Then, the influence of grating structure parameters and cladding diameters on sensitivity of dual-peak based LPFG is discussed and it is found that the grating periods affect the sensitivity, linearity and the range of strain. And the grating lengths have a valid influence on the peak and width,which directly concerns the precision of peek-peak. The results show that the sensitivity could effectively be improved by two orders of magnitude compared with that of the conventional LPFG strain sensor, if selecting the appropriate grating structure parameters and cladding radii. The research provides theoretical foundation for structural optimization of dual-peak resonant LPFG strain sensors with high sensitivity.