A fiber-optic sensor is a sensor that uses optical fiber either as the sensing element ("intrinsic sensors"), or as a means of relaying signals from a remote sensor to the electronics that process the signals ("extrinsic sensors"). Fibers have many uses in remote sensing. Depending on the. A fiber optic sensor measures a physical quantity by modulating the intensity, spectrum, phase, or polarization of light traveling through the optical fiber system. Radiation absorption creates electronic excited states that are trapped by localized defects for extended periods of time. In 2023, researchers turned submarine cables into earthquake warning systems and gave electric vehicles “optical nerves” to prevent battery failures.