Lab-to-Field Transition in FBG Sensors: A Quantitative Assessment of Literature-Reported Deployment Maturity

Fiber Bragg Grating (FBG) sensors have become an important sensing technology owing to their high sensitivity, multiplexing capability, and ability to operate in demanding environments. Despite extensive research activity, the transition of FBG sensing systems from laboratory studies to practical deployment remains uneven across application domains. This review examines that transition through a multi-level assessment combining publication trends, deployment maturity, application domains, and sensing performance. The analysis of publications from 2021 to 2026 shows that most of the reported systems remain at the laboratory-validation stage, while examples of short-term field deployment and long-term operational deployment remain comparatively limited. Marked differences were observed between various application domains. Structural health monitoring and several harsh-environment applications provide the strongest evidence of literature-reported field deployment, whereas biomedical and chemical sensing systems remain concentrated at lower maturity levels despite intensive research activity. The results suggest that deployment maturity is influenced by the relationship between the sensing mechanism and the target measurand, integration requirements, environmental robustness, system complexity, and application demand. Overall, the findings indicate that the principal challenge facing FBG sensing technology is no longer sensing performance itself, but the ability to achieve reliable, scalable, and sustainable operation under real service conditions.