Raman optical fiber sensing is based on the principle of Raman scattering, that is, a type of optical scattering where the interaction of a pulsed light with molecular motion changes the frequency of the incoming light when it passes through the sensing fiber 56. Discrete OFS enable measurement at a single point and are mainly based on Fiber Bragg Gratings (FBGs), which exhibit reflectivity whose center wavelength varies with strain/temperature. A number of them can also be inscribed along the same fiber to make quasi-distributed measurements using. 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. Raman distributed optical fiber sensing has been demonstrated to be a mature and versatile scheme that presents great flexibility and effectivity for the distributed temperature measurement of a wide range of engineering applications over other established techniques.
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