This course consists of a series of lectures to introduce how a light signal can be used to measure the most common physical quantities such as distance, displacement, speed, acceleration, temperature, mechanical forces and deformation.

The course serves a twofold purpose. First, it gives an overview of the different physical mechanisms through which an optical sensor changes the characteristics of a light signal by allowing it to interact with a physical measurand. We therefore review the most important characteristics of an optical signal, such as coherence, polarization, wavelength, intensity, and phase, the principles of interferometry, the Bragg condition, and the elasto-optic effect.

Second, it describes how optical sensors are built, what their main specifications are, and which aspects one has to consider for building an effective sensor.

Both free-space optical sensors and optical fiber sensors are investigated. Free-space sensors are applied to the measurement of distance and displacement; speed and acceleration; and temperature. This includes techniques such as time-of-flight (e.g., LiDAR), interferometric displacement sensors, and infrared thermometry using blackbody radiation.

Optical fiber point sensors based on interferometry, Bragg gratings, or distributed sensing are compared, and the potential of multiplexing is studied. Specific types such as Fabry-Pérot, Mach-Zehnder, and Michelson interferometers in fiber are discussed, as well as distributed techniques like OFDR (Optical Frequency Domain Reflectometry).

The practical component includes laboratory work with FBG and OFDR-based sensors for strain and temperature sensing, and a poster assignment where students present recent research on experimental optical sensors.