A Comprehensive Review of Optical Fiber Sensors: Principles, Technologies and Applications

Optical fiber sensors (OFSs) have emerged as one of the most promising sensing technologies owing to their high sensitivity, compact size, immunity to electromagnetic interference, corrosion resistance, and capability for distributed and remote sensing. These unique characteristics have enabled their widespread adoption in structural health monitoring, biomedical diagnostics, aerospace engineering, industrial automation, environmental monitoring, telecommunications, and electrical power systems. The rapid development of advanced optical materials, fiber fabrication techniques, photonic integrated circuits, and artificial intelligence-assisted signal processing has further expanded the capabilities and application domains of optical fiber sensing technologies. This review presents a comprehensive analysis of the operating principles, classifications, mathematical foundations, and recent technological advancements in optical fiber sensors. The major sensing mechanisms, including intensity modulation, wavelength modulation, phase modulation, and polarization modulation, are systematically discussed together with representative sensor configurations such as Fiber Bragg Grating (FBG), Fabry–Perot, Michelson, Mach–Zehnder, Sagnac interferometric, fluorescence-based, and evanescent-wave sensors. The fundamental mathematical relationships governing light propagation, total internal reflection, Bragg resonance, interferometric phase modulation, and evanescent-field sensing are also reviewed to provide a rigorous theoretical understanding of sensor operation. The paper critically compares recent review articles published between 2020 and 2026 and highlights the distinctive contributions, advantages, limitations, and emerging research trends of different optical sensing technologies. Furthermore, representative applications in transformer condition monitoring, structural health monitoring, biomedical instrumentation, aerospace systems, oil and gas industries, environmental sensing, and smart-grid monitoring are comprehensively summarized. The review reveals that Fiber Bragg Grating and distributed optical fiber sensors presently dominate structural monitoring applications because of their high multiplexing capability, while interferometric sensors continue to provide superior sensitivity for precision measurements. Recent integration of machine learning, Internet of Things (IoT), photonic integrated circuits, and distributed optical sensing is transforming conventional optical sensing into intelligent sensing systems capable of real-time monitoring and predictive diagnostics. Finally, the paper identifies current research challenges and discusses future directions toward miniaturized, multifunctional, AI-enabled, and quantum-enhanced optical fiber sensing technologies.