The fiber optic sensor has an optical fiber connected to a light source to allow for detection in tight spaces or where a small profile is beneficial. A fiber optic sensor measures a physical quantity by modulating the intensity, spectrum, phase, or polarization of light traveling through the optical fiber system. Fibers have many uses in remote sensing. 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. Fiber optic sensors represent a cutting-edge technology used in a variety of industries to detect and measure changes in physical parameters such as temperature, pressure, vibration, and strain. This article will explore the principles behind fiber optic current sensors.