基于单模-无芯-单模结构的光纤折射率传感器

A refractive index sensor based on single-mode no-core single-mode fiber structure

提出了一种基于光纤单模-无芯-单模结构的光纤折射率传感器。当外界折射率(SRI,surroundingrefractive index)小于无芯光纤(NCF,no-core fiber)折射率,并且二者十分接近的情况下,NCF可以看作是具有阶跃折射率分布的弱导多模光纤(MMF),这样便构成了传统的单模-多模-单模(SMS,single-mode multimode single-mode)光纤结构。利用线偏振模近似的方法理论分析了基于这种光纤结构的折射率传感器的模式激发特性以及输出特性,进而进行了相应的数值仿真及实验验证,结果表明,数值仿真与实验结果均与理论分析结果相一致。在1.3～1.4的折射率范围内,实验测得传感器灵敏度达到205.42 nm/RIU。

A refractive index sensor based on single-mode no-core single-mode fiber structure is proposed and experimentally demonstrated. When the difference between surrounding refractive index （SRI） and the refractive index o{ no-core fiber （NCF） is relatively small,the NCF can be treated as a weakly guid- ing multimode fiber with step-index profile, consttructing the traditional single-mode multimode single- mode （SMS） fiber structure. Under the weakly guiding condition, the mode excitation and the output characteristics of this sensor are analyzed by using linear polarization mode approximation method. And numerical calculations are carried out based on the theoretical analysis. Numerical simulations show that the characteristic wavelength in the output spectrum will shift as the SRI changes, which reflects the re- fractive index sensing capability of this fiber structure. For verifying testify the conclusion of the numeri- cal simulation, several experiments have been carried out. As the SRI increases, the characteristic wave- length shows blue shift correspondingly ,which agrees well with the numerical simulation and the theo- retical anticipation. The sensitivity of this sensor obtained from experiments reaches 205.42 nm/RIU for a refractive index range from 1.3 to 1.4. And a further confirmatory experiment for testing the absolute ethylalcohol in room temperature indicates that such a refractive index sensorrs relative error is 0.1%.