利用镀自组装薄膜的双峰谐振长周期光纤光栅（LPFG）实现了高灵敏的折射率传感，给出了提高镀膜双峰谐振光纤光栅对环境折射率（SRI）灵敏度的途径。确定最佳镀膜厚度，使光纤包层模位于模式转换区附近；调整光纤半径，使镀膜后光栅的双峰位于相位匹配转折点(PMTP)附近，给出了确定最优膜厚和光纤半径的方法。将不同半径的双峰光栅镀自组装聚丙烯胺盐酸盐(PAH)/聚丙烯酸 (PAA)薄膜后，放入不同浓度的葡萄糖溶液中进行折射率传感实验。结果表明：通过优化光纤半径和薄膜厚度，镀膜后工作于模式转换区附近和PMTP附近的双峰光栅对1.333~1.372范围内折射率的灵敏度高达3985 nm/RIU（RIU为单位折射率），明显高于不在模式转换区或PMTP附近的光栅，亦高于已报道的非双峰镀膜长周期光纤光栅。

Highly sensitive refractive index sensing is realized by using dual-peak resonance long-period fiber grating (LPFG) with self-assembled coating. The way for improving the sensitivity of coated dual-peak resonance fiber gratings to the surrounding refractive index is given. The fiber cladding mode is located near the mode transition zone by choosing optimal film thickness. The dual-peak structure of fiber coated is located near phase-matching turning point (PMTP) by adjusting the fiber radius. The method for determining optimal film thickness and fiber radius is given. Dual-peak gratings with different fiber radii coated with poly allylaminehydrochliride (PAH)/ poly acrylic acid (PAA) films are immersed in different concentrations of glucose solution to carry out refractive index sensing experiments. Results show that the sensitivity of coated dual-peak gratings operating near mode-transition regions and PMTP is 3985 nm/RIU in 1.333~1.372 index range, which is obviously higher than those of gratings not operating near mode-transition or PMTP, and also higher than that of non-dual-peak coated LPFGs reported.