A Thin-Core Fiber Modal Interferometer for Liquid-Level Sensing
XU Ben1, LI Jian-Qing1*, LI Yi2, DONG Xin-Yong2
1Faculty of Information Technology, Macau University of Science and Technology, Macao SAR 999078 2College of Optical and Electronic Technology, China Jiliang University, Hangzhou 310018
Abstract：A fiber-optic liquid-level sensor is proposed and experimentally demonstrated. It is a Mach–Zehnder interferometer (MZI) composed of a thin-core single-mode fiber (TCSMF) without coating sandwiched between two single-mode fibers (SMFs). The transmission spectrum properties of the MZI modified by liquid around the TCSMF are used for detecting the liquid level. It is found that the sensor exhibits an excellent linear relationship between the level and the shift of interference dip wavelength and its achieved sensitivities are 0.160 nm/mm and 0.288 nm/mm for liquid with an RI of 1.3330 and 1.3696, respectively. Employing the spectrum differential integration (SDI) method to analyze transmission spectra can increase the detecting resolution of the liquid level. Due to its advantages of an extremely easy fabrication process, high sensitivity and a large sensing range, the sensor is an ideal candidate for continuous liquid level sensing.
2012, Vol. 29 
