倏逝波在锥形光纤折射率计中的传感作用

对锥形光纤模间干涉结构产生的倏逝波与模式有效折射率间的关系进行了理论计算与研究,并仿真得出随着外界折射率变化而移动的干涉光谱,以此在理论方面证明倏逝波的产生对提高波长解调型的锥形模间干涉折射率传感器的灵敏度起着至关重要的作用.基于倏逝波的吸收光谱法计算了锥形区域在不同轮廓线、不同锥区长度以及不同锥径时的倏逝波强度,对优化锥区形状提高折射率测量的灵敏度有所帮助.最后以拉锥的模间干涉光纤传感结构测量折射率的实验验证了理论计算的正确性.

Sensory Effect of Evanescent Wave in the Tapered Optical Fiber RI Sensor

The internal mechanism about the effect of evanescent wave in tapered modal interferometer was investigated theoretically. The relationships between the power of evanescent wave and the effective RI of cladding modes were calculated， and the simulated interference spectrum shifted with external RI was ohtained.It can be theoretically proofed that the generation of evanescent wave provides a vital role in improving the sensing sensitivity of tapered optical fiber RI sensor. In addition， effects of the taper shape， such as outline， waist radius and taper length， on the power of evanescent wave attenuated in taper region were investigated based on the evanescent wave absorption spectroscopy， which is helpful to optimize the taper shape and improve the sensitivity of RI measurement. Finally， the experiment of RI measurement by tapered modal interferometer has been carried out to verify the accuracy of the theory.