基于严格的相位匹配公式,在充分考虑材料色散的基础上,详细研究了镀膜长周期光纤光栅的双峰谐振效应。研究发现,随着环境折射率的变化,发生谐振的双峰也发生变化,且变化趋势相反。给出了镀膜长周期光纤光栅双峰谐振波长之间的距离随环境折射率变化的关系,并与普通长周期光纤光栅的同等情形进行了比较,发现镀膜长周期光纤光栅的双峰谐振能够极大提高长周期光纤光栅的折射率灵敏度。但由于发生双峰谐振需要的包层模式次数较高,故其探测范围比应用低次耦合的单峰探测范围要窄。 Based on the strict phase matching formula, the bimodal resonance of coated long-period fiber gratings is studied in detail based on the material dispersion. The study found that with the change of the refractive index of the environment, the double peaks that resonate also change, and the changing trend is the opposite. The relationship between the bimodal resonant wavelength and the refractive index of the long-period fiber grating is given and compared with the same situation of the ordinary long-period fiber grating. It is found that the bimodal resonance of the long-period fiber grating can be extremely Increase the refractive index sensitivity of long-period fiber gratings. However, due to the occurrence of bimodal resonance requires a higher number of cladding modes, the detection range is narrower than the one-shot detection range using low-order coupling.