Optical sensors are increasingly important in avionics due to their precision, reliability, and ability to operate in extreme conditions. Among them, fiber optic sensors, being all-dielectric structures and not requiring copper wires, stand out for their immunity to electromagnetic interference, making them ideal for applications in which signal integrity is fundamental, as in aircraft environments. Moreover, fiber optic sensors are lightweight and can be easily integrated into structures, in particular composite materials. All this leads to the new paradigm of the “fly-by-light” approach, for which not only command signals are transmitted through optical fibers, but also aircraft control systems rely on optical methods for navigation information and to measure various parameters such as pressure, temperature, and structural deformations. One of the most relevant and already widely deployed applications of photonics in avionics is optical gyroscopes, which are used for inertial navigation, offering reliable and accurate orientation and position data without having to rely on external signals. Another emerging application of optical sensors is in the development of “smart structures”, in which they contribute by enabling the detection of the early onset of structural health issues, such as cracks or deformations. These and other new uses of optical sensors are enabling real-time monitoring of aircraft components, enhancing safety while simultaneously reducing downtime and thus operating costs.