A fiber optic sensor measures a physical quantity by modulating the intensity, spectrum, phase, or polarization of light traveling through the optical fiber system. It's a device that converts light rays into electronic signals. Radiation absorption creates electronic excited states that are trapped by localized defects for extended periods of time. Heating the material enables the trapped states to interact with phonons and decay into lower-energy. This article explores the different types of Fiber Optic Sensors, their working principles, and various applications. We'll delve into Intrinsic, Extrinsic, and Hybrid fiber optic sensors, explaining how they function.