Optical fibers can be used as sensors to measure strain, temperature, pressure and other quantities by modifying a fiber so that the quantity to be measured modulates the intensity, phase, polarization, wavelength or transit time of light in the fiber. 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. Radiation absorption creates electronic excited states that are trapped by localized defects for extended periods of time. However, the current literature contains. Among the reasons why optical fibers are such an attractive are their low loss, high bandwidth, immunity to electromagnetic interference (EMI), small size, light weight, safety, relatively low cost, low maintenance, etc. At the heart of this technology is the optical fiber itself -- a hair-thin. Fiber-optic sensors (also called optical fiber sensors) are fiber -based optical sensors for some quantity, typically temperature or mechanical strain, but sometimes also displacements, vibrations, pressure, acceleration, rotations (measured with optical gyroscopes based on the Sagnac effect), or.