Biofilm Monitoring by Fiber-Optic Sensors: A Review

Biofilms are structured communities of microorganisms embedded in a self-produced matrix, often linked to medical, industrial, and environmental challenges, making their detection and monitoring essential. This work provides a comprehensive overview of fiber-optic sensors for biofilm monitoring, highlighting advances in sensor configurations, measurement techniques, coating strategies, biofilm types, and monitored parameters, with particular emphasis on biofilm thickness and overall performance. The studies are organized based on the measurement configuration, including light intensity, fluorescence intensity, wavelength shifts, spectroscopic features, as well as multi-domain and indirect measurements of biofilm byproducts (such as hydrogen, oxygen, pH, and temperature changes). Emphasis is placed on approaches that monitor the biofilm as a whole rather than individual microorganisms. The aim is to summarize current progress in fiber-optic biofilm sensors and to outline key directions for future research in this rapidly evolving field.