Bow Tie-Shaped Fiber Structure: Toward Dual-Channel Sensing Device for Hydrogen Peroxide Detection in Full-Fat and Skim Milk

Milk adulteration is one of the pervasive global practices for economic benefits since it is consumed as a crucial source of dairy products in every part of the world. Hydrogen peroxide (H<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>O<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>) is one of the most common adulterants added to milk to inhibit the growth of microorganisms and extend its shelf life. The adulteration of milk with high concentrations of H₂O₂ poses serious health risks to consumers. To address this, we present a dual-channel optical fiber sensor based on a novel bow-tie-shaped Mach-Zehnder interferometer (MZI) to measure H<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>O<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> concentration in full-fat and skim milk simultaneously. The bow-tie-shaped MZI was constructed by forming two loops from a single-mode fiber (SMF) with various bending diameters labeled as Channel 1 and Channel 2, using a thin capillary tube. The dual-channel MZI generates two separate interference dips, namely dip1 and dip2, within a specific wavelength range. The two dips shift with the variation of H<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>O<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> concentration in milk, and simultaneous measurement of H<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>O<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> concentration in full-fat and skim milk can be realized. The proposed dual channel sensor shows a high performance of achieving 119.14 nm/% sensitivity with R<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> of 99 % and 158 nm/% with good linearity of 98.6 % for full-fat milk and skim milk, respectively. The proposed sensor presents the development of a low-cost and compact dual-channel optical fiber sensing device based on the macro bending loss for accurate and simultaneous measurements.