Experimental study of liquid refractive index sensing based on a U-shaped micro-fiber

摘要

A U-shaped micro-fiber sensing system designed to measure the refractive index of liquid had been proposed. The sensing mechanism of U-shaped micro-fiber was discussed. A general single-mode fiber was bent into U-shaped and the cladding of U-shaped fiber was corroded by HF acid buffer solution. Powers of U-shaped micro-fiber with different diameters had been measured by many experiments and the appropriate designed parameters were obtained. Then, this U-shaped micro-fiber was immersed in liquids, such as pure water, ethanol, acetone and isopropanol. The evanescent field of the U-shaped fiber should be modulated by the liquid and the optical signal in the U-shaped micro-fiber was measured by the optical spectrum analyzers (OSA). Experimental results were analyzed. The spectra in the air were selected as a reference and the relative intensity of different liquids was obtained. These results showed that the relative intensity of the liquid had a good linear relationship. This sensing device could accurately demarcate refractive index of liquid. It is simple, low cost, and it can also be applied in measuring the level of liquid. (C) 2015 Elsevier GmbH. All rights reserved.