This review offers a comprehensive analysis of recent advances in optical fiber-based pH sensors, covering key techniques such as fluorescence-based, absorbance-based, evanescent wave, and interferometric methods. 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. While pH determination is a commonplace laboratory practice, conventional commercial pH probes exhibit drawbacks of bulkiness, slow response times, and signal drift. PreSens is a world leader in the field of optical sensor technology.