Abstract
A fiber optic sensor sensitive to refractive index changes of the outer region of the fiber cladding is presented. The sensor uses bent plastic optical fibers in different bending lengths to increase sensitivity. Measurements were made for low-fat milk, the refractive index of which is altered by some preservatives such as formaldehyde, hydrogen peroxide, and sodium carbonate. Concentrations of the preservatives in the milk were changed between 0% and 14.3% while the refractive indices occurred between 1.34550 and 1.35093 for the minimum (0%) and maximum (14.286%) concentrations of sodium carbonate, respectively. Due to bending-induced sensitivity, the sensor is able to detect refractive index changes less of than 0.4%. The results show that there is excellent linearity between the concentration and normalized response of the sensor.
Highlights
Technological developments have made every area of our lives easier
In a multimode plastic optical fiber (POF), the light is guided by total internal reflections that occur in core-cladding interface of the fiber as shown in Figure 1a [26]
A fiber optic sensor made by bent plastic optical fibers has been presented
Summary
Technological developments have made every area of our lives easier. One of the developments has taken place in the food industry because biosensor-based sensing technologies offer advantages in industrial processes and in health and chemical ones [1]. Because of the fact that they can carry harmful bacteria and microorganisms, they can spoil the products and make people sick. For this reason, many researchers have attempted to develop biosensors for detecting compositions and some contaminants such as enterotoxins, antibiotics, bacteria, aflatoxins [5,6,7,8,9] and monitoring some critical parameters such as the cutting time, pH, temperature, and enzyme concentration [10,11,12,13,14,15,16] in milk and its products
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