LPFG折射率模式响应及其在传感建模中的应用

Mode Response of LPFG to the Refractive Index of External Medium

摘要:

基于光纤光栅的模式耦合理论,采用严格的数学模型,给出了三层介质长周期光纤光栅(LPFG)的纤芯模和包层模的本征方程,分析了长周期光纤光栅中的纤芯模式和包层模式的有效折射率随外界环境折射率变化的情形,以及外界环境折射率变化对长周期光纤光栅谐振波长的影响。通过在长周期光纤光栅外涂覆折射率对外界环境变化敏感响应的特定薄膜可以显著提高其传感测量的灵敏度。研究结果可为长周期光纤光栅传感器结构参数的优化设计和实际应用提供理论支持。

Abstract:

Based on coupled-mode theory, the eigen equations of core and cladding modes of the three-layer dielectric long-period fiber grating (LPFG) are presented by using strict mathematical model. Changes of effective indexes of the core and cladding modes in LPFG with refractive index of external environment are described, and the influence of the changes of the refractive index of external medium on resonant wavelength of LPFG is analyzed. The sensitivity of sensing measurement of LPFG can be significantly improved by coating with a specific film whose refractive index is sensitive to the change of the external environment, which provides a theoretical support to the optimum design of LPFG sensor and its practical application.