The fiber optic sensor is based on a Mach-Zehnder interferometric technique, where the pH sensitive material is coated on a short, typically 20-25 mm thin core fiber spliced between two standard single mode fibers. The working principle of the sensor is simulated by using COMSOL. Measuring pH is a critical parameter in environmental monitoring, biomedical diagnostics, food safety, and industrial processes. Optical fiber sensors have proven highly effective for pH detection due to their exceptional sensitivity, rapid response, and resistance to electromagnetic interference. A fiber optic pH sensor based on single fiber phase fluorescence lifetime measurements of commercially available fluorescence indicators is described. While pH determination is a commonplace laboratory practice, conventional commercial pH probes exhibit drawbacks of bulkiness, slow response times, and signal drift. These become particularly limiting in specialized fields like tissue engineering and bio-industrial processing, where unique pH probe. Advancements in Optical Fiber Sensors for pH Measurement: Technologies and Applications Academic Editors: Flavio Esposito, Stefania Campopiano and Agostino Iadicicco Received: 29 May 2025 Revised: 4 July 2025 Accepted: 7 July 2025 Published: 9 July 2025 Citation:Alhussein, A. Methods: A fabrication process, including sol–gel synthesis.