This article is Work in Progress.
Fiber optics are commonly used in communication networks. These are very thin strands (similar to human hair) of glass, are flexible as a fabric thread and are often shipped on reels.
An outer protective coating is applied to save from environment.
Optical fibers make use of "total internal reflection" principle, where the light is trapped inside the fiber, because the angle of incidence consistently stays greater than the critical angle and travels within it. Hence there is a limit, defined by the critical angle and reflective index of the material, to how much an optical fiber can be turned/twisted before it loses its ability to transmit. Laser light of different wavelengths, that is different colors, is used to constantly interrogate fiber, changes in the physical properties, like temperature and stress, affects the laser light transmission within the fiber. Studying these changes in light, one can measure the change in temperature and/or stress.
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