Fiber optic sensors in Portugal commonly include Fiber Bragg Grating (FBG) sensors, interferometric sensors, and intensity-based sensors, widely used in structural monitoring, industrial applications, and biomedical research.

Types of Fiber Optic Sensors

Fiber Bragg Grating (FBG) Sensors FBG sensors are among the most widely used in Portugal, particularly for structural health monitoring and industrial applications. They work by reflecting specific wavelengths of light that shift in response to strain or temperature changes, allowing precise measurement over long distances. Companies like HBK FiberSensing in Porto specialize in FBG-based sensors, interrogators, and accessories, providing both standard and customized solutions for OEMs and critical infrastructure monitoring . Interferometric Sensors These sensors measure changes in phase, polarization, or optical path length caused by external physical parameters. Interferometric fiber optic sensors are used in high-precision applications, including vibration monitoring, pressure sensing, and laboratory research. INESC TEC and other Portuguese research institutions have historically contributed to the development of interferometric and reflective fiber optic sensors . Intensity-Based Sensors Intensity-modulated fiber optic sensors detect changes in light intensity caused by variations in the measurand, such as displacement, pressure, or chemical concentration. These sensors are simpler and cost-effective, suitable for industrial automation and environmental monitoring . Other Specialized Sensors

• Optical Current Sensors: Used in electrical power systems to measure current without electromagnetic interference .
• Functional Near-Infrared Spectroscopy (FNIRS) Sensors: Employed in biomedical applications to monitor brain activity and oxygen saturation using red and infrared light .
• Multiplexed Fiber Arrays: Allow multiple sensors to operate along a single fiber, enabling distributed sensing over long distances .

Advantages and Applications

Fiber optic sensors in Portugal benefit from the intrinsic properties of optical fibers: they are electromagnetically passive, chemically inert, and capable of long-distance and distributed sensing. These features make them ideal for:

• Structural health monitoring of bridges, buildings, and pipelines
• Industrial process control and automation
• Biomedical and physiological monitoring
• Environmental sensing in harsh or remote locations

Key Manufacturers and Research Institutions

• HBK FiberSensing (Porto): FBG sensors and systems for industrial and infrastructure monitoring
• INESC TEC: Research and development in interferometric, reflective, and Bragg grating sensors
• PLUX: FNIRS sensors for biomedical applications
• Sarspec: Optical fibers and probes for spectroscopy and measurement systems These organizations highlight Portugal's strong presence in both research and commercial deployment of fiber optic sensor technologies.