Advanced intensity-modulated fiber sensors for scalable sensing

Intensity-modulated fiber optic sensors (IM-FOSs) represent a cost-effective and structurally simple alternative to phase-based and wavelength-based optical sensors. Their operational principle enables the development of robust, scalable, and multiplexable systems suitable for a wide range of mechanical measurements. This review provides a structured overview of IM-FOS technologies, highlighting recent developments in architectures, interrogation methods, and application domains. An analysis with interferometric and Bragg-grating-based sensors is presented to clarify the trade-offs in sensitivity, complexity, and cost. Especially in industrial and civil monitoring, IM-FOSs offer unique advantages in terms of simplicity and adaptability. Finally, key research directions are outlined, including the integration of machine learning algorithms, the use of hybrid materials and smart structures, strategies to improve long-term stability, miniaturization and commercialization potential, and the pressing need for standardization. The article aims to provide a comprehensive reference for researchers and engineers seeking to develop or deploy intensity-based optical sensing systems.