A simple fiber tip sensor for refractive index (RI) measurement based on Fabry-Perot (FP) interference modulated by Fresnel reflection is proposed and demonstrated. The sensor head consists of an etching-induced micro air gap near the tip of a single-mode fiber. The microgap and the fiber tip function as two reflectors to form a FP cavity. The external RI can be unambiguously measured by monitoring the fringe contrast of the interference pattern from the reflection spectrum. The experimental results show that the proposed sensor achieves temperature-independent RI measurement with good linear response. The proposed sensor achieves a high RI resolution of up to 3.4 \times 10?5 and has advantages of low cost and easy fabrication.
© 2012 Chinese Optics Letters
Fiber Optics and Optical Communications
Yue Ma, Xueguang Qiao, Tuan Guo, Ruohui Wang, Jing Zhang, Yinyan Weng, Qiangzhou Rong, Manli Hu, and Zhongyao Feng, "Temperature-independent refractive index measurement based on Fabry-Perot fiber tip sensor modulated by Fresnel reflection," Chin. Opt. Lett. 10, 050603- (2012)