We theoretically and experimentally demonstrated the existence of dual loss peaks in the transmission spectrum of long-period fiber gratings (LPFGs) fabricated in a parameter-optimized two-mode fiber for the mode coupling between LP₀₁ and LP₁₁ modes by CO₂ laser. The two dips moved in opposite directions with decreasing grating period and merged at a critical grating period. The strain and temperature sensitivities of the two resonant dips were 10 times those of the unoptimized LPFG. An LPFG-aided interferometric sensor with high modulation depth and low insertion loss was fabricated. The LPFG-based sensor and LPFG-aided interferometric sensor can be used for strain and temperature discrimination with high sensitivity.

我们在理论上和实验上证明了在参数优化的双模光纤中制造的长周期光纤光栅（LPFG）的透射光谱中存在双损耗峰，用于CO ₂激光器在LP ₀₁和LP ₁₁模式之间进行模耦合。两次下降沿相反方向移动，光栅周期减小，并在临界光栅周期合并。两个谐振骤降的应变和温度灵敏度是未优化的LPFG的应变和温度灵敏度的10倍。制造了具有高调制深度和低插入损耗的LPFG辅助干涉传感器。基于LPFG的传感器和LPFG辅助的干涉式传感器可以高灵敏度地用于应变和温度判别。