Yang Jingyi, Dong Xinyong, Ni Kai, Chan Chi Chu, Shun Perry Ping
Appl Opt. 2015 Apr 1;54(10):2620-4. doi: 10.1364/AO.54.002620.
A relative humidity (RH) sensor in reflection mode is proposed and experimentally demonstrated by using a polyvinyl alcohol (PVA)-coated tilted-fiber Bragg grating (TFBG) cascaded by a reflection-band-matched chirped-fiber Bragg grating (CFBG). The sensing principle is based on the RH-dependent refractive index of the PVA coating, which modulates the transmission function of the TFBG. The CFBG is properly designed to reflect a broadband of light spectrally suited at the cladding mode resonance region of the TFBG, thus the reflected optical signal passes through and is modulated by the TFBG again. As a result, RH measurements with enhanced sensitivity of ∼1.80 μW/%RH are realized and demodulated in the range from 20% RH to 85% RH.
提出了一种反射模式的相对湿度（RH）传感器，并通过使用涂覆有聚乙烯醇（PVA）的倾斜光纤布拉格光栅（TFBG）与反射带匹配的啁啾光纤布拉格光栅（CFBG）级联进行了实验验证。传感原理基于PVA涂层与相对湿度相关的折射率，该折射率调制了TFBG的传输函数。CFBG经过合理设计，可反射在TFBG包层模共振区域光谱上合适的宽带光，因此反射光信号通过TFBG并再次被其调制。结果，实现了在20%相对湿度至85%相对湿度范围内解调，灵敏度提高到约1.80 μW/%RH的相对湿度测量。
