设计了一种基于模间干涉的亚波长直径光纤气体折射率传感方案,并分析了其测量灵敏度.将标准单模光纤和一段仅传输基模与二阶模的无包层亚波长直径光纤结合形成传感头,通过分析传感头外气体折射率的变化对两个模式干涉谱峰值移动的影响,研究了这种传感器的折射率测量灵敏度.结果表明,这种传感器的灵敏度高于利用折射率引导型光子晶体光纤的基于模间干涉的折射率传感器.因为没有气体向微孔扩散的过程,这种基于模间干涉的亚波长光纤折射率传感器可用于实时探测.

A gas refractive index sensor with subwavelength-diameter fiber (SDF) based on intermodal interference is designed and its sensitivity is analyzed.The sensor head is formed by splicing a standard single-mode fiber with a stub of SDF without cladding,which only supports the fundamental mode and the 2nd-order mode.The sensor′s sensitivity is analyzed according to the peaks shift of the interference spectrum,which is caused by the refractive index change of the gas outside the sensor head.It is found that the sensitivity of this sensor is higher than the one based on intermodal interference using index-guided photonic crystal fiber (PCF).Since there is no process of gas diffusing into the micro-holes compared with the PCF,therefore this sensor can be used for real-time detecting.