The research on optical fiber sensors produced and still continues to give life to a variety of measurement techniques for different applications. Optical fiber sensors operate by modifying one or more properties of the light passing through the sensor, when the parameter to be measured changes. Intensity-based sensors represent one of the earliest and perhaps the simplest type of optical fiber sensors. Among the transmission and reflection systems reported, there are several transduction mechanisms, namely, evanescent wave–based sensors and spectrally based sensors. The principle of operation of a wavelength-based sensor system consists in monitoring the resonance wavelength shift caused by a perturbation. Most wavelength-modulated sensors are based on fiber Bragg gratings (FBGs). The most common FBG inscription methods include the phase mask, interferometric, and point-by-point techniques. Multiparameter measurement using fiber sensors is a challenging topic, while it enables the minimization of size, cost, and complexity of sensing systems.