Case Study of Multifunctional Fiber Optic Sensor

Fiber optic sensors have been successfully applied in structural health monitoring of dams, bridges, and tunnels, providing high-resolution, real-time data on strain, temperature, and deformation.Concrete Dam MonitoringA study on concrete dams utilized Raman-type Distributed Fiber-Optic Sensors (DFOSs) and Bragg grating-type Localized Fiber-Optic Sensors (LFOSs) to monitor temperature variations. Raman DFOSs offered high spatial resolution and comprehensive thermal mapping, detecting detailed thermal phenomena such as cooling effects in dam galleries and significant thermal gradients that conventional sensors could not capture. LFOSs provided localized, reliable measurements with multiplexing capabilities, reducing the number of cables required and simplifying installation. Both technologies demonstrated data quality comparable to conventional sensors, enhancing structural health monitoring systems for dams .Bridge MonitoringIn a prestressed reinforced concrete viaduct, fiber optic deformation sensors were embedded during construction to monitor strain and displacement. The sensors allowed engineers to track stress variations during different construction phases, including pier casting and deck launching. This real-time monitoring enabled accurate assessment of structural safety and serviceability, early detection of potential issues, and informed maintenance planning. The system also helped evaluate shrinkage effects and load responses, providing a cost-effective tool for long-term bridge safety management .Tunnel and Underground Structure MonitoringDistributed fiber-optic sensing was applied to monitor tunnels, including a new Crossrail station tunnel and a century-old cast iron tunnel. Brillouin-based time domain techniques were used to measure strain in sprayed concrete linings and assess structural integrity during excavation and nearby construction activities. These sensors enabled early-stage implementation of long-term structural health monitoring programs, providing continuous data for safety assessment and maintenance planning in underground environments .Advanced Fiber Optic Sensor TechniquesAdditional case studies highlight novel fiber optic sensing methods, such as:Absolute position measurement using white-light channeled spectrumRough surface height distribution via low-coherence interferometryWide-dynamic range low-coherence interferometryOptical coherence tomography with enhanced resolution These techniques demonstrate the versatility of fiber optic sensors in precision measurement and high-resolution monitoring across various engineering and scientific applications .SummaryFiber optic sensors, including distributed and localized types, provide high accuracy, real-time monitoring, and reduced installation complexity. They are widely applied in civil infrastructure, underground structures, and precision measurement systems, offering significant advantages over conventional sensors in terms of spatial resolution, multiplexing, and long-term reliability .