镀膜长周期光纤光栅传感器是目前光纤光栅传感研究的一个热点,但关于此类传感器模型的全面的理论分析目前还很少。本文基于严格的四层模型,从理论上对芯层折射率调制为矩形波调制的薄膜长周期光纤光栅的特性进行了详细的分析。在充分考虑材料色散对光纤芯层和包层的影响后,对薄膜参数、占空比和环境折射率的变化对镀膜长周期光纤光栅的谱特性的影响进行了数值研究。研究结果表明,薄膜参数对透射谱有重要影响,合理设计薄膜厚度可以获得较佳的损耗峰。研究还发现,镀膜后占空比对透射谱的影响减小,而对环境折射率变化的敏感度增加。在占空比为0.5时光栅具有最大的损耗峰值。

The long period fiber grating sensor coated with film is popular in the research of the long period fiber grating sensing. General theoretical analysis of the sensor model is few at present. The characteristics of the long period fiber grating with thin film overlay with a index rectangle modulation is analyzed theoretically in detail based on strict four layer model. Numerical analysis is carried out aiming at the change of the spectrum characteristics with the thin film parameter, duty cycle and surroundings refractive index. Research shows that the thin film has significant effect on the transmission and loss peak can obtain preferable by designing of thickness of the thin film rationally. Results shows the duty cycle for the LPFG with film overlay decreases on the role of the transmission spectrum and the film thickness increase the sensitivity of the surrounding refractive index. LPFG has the maximum loss peak value when duty cycle is 0.5.