Abstract
A noncontact optical fiber sensor for measuring the refractive index of transparent liquids is proposed. It operates by calculating the path of a focused laser beam at 635 nm that travels across the boundaries of a liquid sample. The optical power Fresnel reflections are detected and, subsequently, the refractive index is determined as the ratio between the traveled beam paths when the liquid is deposited versus a reference without the liquid sample. Additionally, a mathematical analysis of the geometrical case is included. The theoretical data from our sensor are in good agreement with the experimental results. The resolution achieved by the sensor is better than 10−3 RIU.
Highlights
In recent years, sensor devices have been widely used for physical and chemical quantities measurements in some manufacturing processes and gadgets such as small size and high sensitivity sensors [1]
A noncontact optical fiber sensor for measuring the refractive index of transparent liquids is proposed. It operates by calculating the path of a focused laser beam at 635 nm that travels across the boundaries of a liquid sample
A well-known device typically used for this purpose is the traditional Abbe refractometer [2] or in a similar way one can find setups that employ the ray deviation through a glass-liquid interface to measure the refractive index of transparent liquids [3,4,5]
Summary
Sensor devices have been widely used for physical and chemical quantities measurements in some manufacturing processes and gadgets such as small size and high sensitivity sensors [1]. Fiber-optic based sensors have, the same advantages attributable to other sensors plus the advantages owing to their waveguide, their electromagnetic immunity, and their remote sensing capability, among others Regarding these novel devices, there are a couple of research groups [6, 7] who demonstrated that, by using the Fresnel reflections exhibited at the liquid-glass interface of fiber probes, it is possible to obtain a ratio between a reference and a test signal to calculate liquids refractive indices. Refractive indices of the tested liquids were measured at a wavelength of 635 nm and with a resolution of 10−3 RIU
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