Applications of optical fiber sensors in marine observation: a review

Abstract Accurate, continuous, and in situ monitoring of marine environmental parameters and their dynamic changes is essential for understanding oceanic processes, predicting ecological evolution, and ensuring safety in marine engineering and national defense. However, in harsh marine environments, conventional electrochemical sensors face limitations such as susceptibility to electromagnetic interference, poor corrosion resistance, and signal loss over long distances, making it difficult to meet the urgent requirements for large-scale, multiparameter, synchronized monitoring with a high spatiotemporal resolution and integrated observations. Optical fiber sensors (OFSs) provide a promising solution to these challenges due to their immunity to electromagnetic interference, corrosion resistance, compact size, high sensitivity, and capability for simultaneous in situ multiparameter sensing. Notably, OFS technology offers the unique potential for ‘communication-sensing integration’ along with strong array and spatial multiplexing capabilities. These features significantly improve the coverage, parameter density, and spatiotemporal resolution of marine monitoring while reducing system complexity and deployment costs. This study reviews recent advances in using OFS technology for monitoring key marine parameters, including temperature, salinity, pressure, pH, and biochemical factors, with a particular focus on point-based sensing technologies, including the use of fiber Bragg gratings, interferometric sensors (Fabry-Pérot, Mach-Zehnder, Michelson, and Sagnac sensors), special optical fiber sensors, surface plasmon resonance fiber sensors, multicore fiber sensors, and fiber laser sensors. The review also covers distributed sensing systems, including quasi-distributed and fully distributed sensing based on Rayleigh, Raman, and Brillouin scattering. The integration of artificial intelligence with ocean sensing is briefly introduced, and an in-depth analysis of sensing mechanisms, performance metrics, and technical issues is provided. This study considers current technological bottlenecks and practical marine applicational requirements and offers an outlook on future research directions for high-performance, reliable, and integrated marine monitoring using OFS systems.