A Review of Optical Fiber Sensors in the Biomedical Field: Toward a Blueprint for Human Health Monitoring

Optical fiber sensors, featuring small size, high sensitivity, immunity to electromagnetic interference, and real-time remote monitoring, are playing an increasingly important role in human health monitoring. This review systematically surveys recent progress from two complementary perspectives: sensing mechanisms (surface plasmon resonance, interferometry, fiber gratings, fluorescence, and intensity modulation) and application forms, with emphasis on wearable integration. Quantitative comparison of representative sensors reveals three trends: plasmonic nanostructures combined with tapered, U-shaped, side-polished, or multicore probes have pushed the detection limits down to femtomolar-to-nanomolar levels for nucleic acids, proteins, and small-molecule biomarkers; interferometric and grating-based sensors enable label-free refractometric detection with sensitivities of 102–104 nm/RIU, yet their practical application is constrained by structural repeatability; and most sensors remain at the proof-of-concept stage in buffer solutions, with only a few validated in real biological samples, and clinical or in vivo validation remains rare. Wearable fiber sensors have matured for joint-motion, respiration, pulse, sweat, blood-pressure, and temperature monitoring, but still face bottlenecks in miniaturization, power consumption, and standardization. On this basis, the review classifies the technology maturity of reported sensors, compares them with competing biomedical sensing technologies, and outlines a milestone-based roadmap toward clinical systems. It thus provides a synthetic framework linking mechanism-level design with application-level integration, serving as a blueprint for translating optical fiber sensing into practical human health monitoring.