Hydrogen peroxide is used in various fields, such as food preservative, bleaching, oxidizing, reducing, and chemical reaction reagents. Herein is described the effort to develop an optical fiber chemical sensor based on the evanescence wave absorbance that can detect the presence of, and measure the concentration of, hydrogen peroxide. For the H₂O ₂ optical fiber sensor, a Nafion membrane was coated on the fiber optic. Titanium ions dispersed in the Nafion membrane can form a TiO-H₂O ₂ complex with the H₂O₂ diffused into the membrane. The complex is shown to absorb light with a maximum absorption near 360 nm. The intensity of the absorbance peak is directly proportional to the concentration of H₂O₂. Additionally, coating polydimethylsiloxiane (PDMS) outside the fiber optic can detect H₂O₂ in high concentration 300ppm and high temperature 70°C. Finally, the use of the developed optical fiber chemical sensor allows the direct determination of H₂O₂ in milk.