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How does a fiber optic cable work?


Over the last couple of years, fiber optic cables transformed the telephone industry. It takes a huge part in making internet available around the world. When Fiber optic cables replace copper, it lowers the costs exponentially. An optical fiber cable is a cable containing one or more optical fibers. The optical fiber elements are typically individually coated with plastic layers and contained in a protective tube suitable for the environment where the cable will be deployed.

A fiber optic cable primarily uses light to transmit data. The inner surface of a fiber optic cable is coated with core and cladding layer, thus enabling total internal reflection due to the difference in the refractive index of the two. One could say fiber optic cables are coated in the inside with a mirror and light travels through the mirrored tube because the mirror reflects light.


We now know how a fiber optic cable reflects light. But how does it transmit data? It’s simple. In digital computing there are only two commands. 0 and 1 which we also call as binary.  So when it comes to a fiber optic cable, light on and light off allows us to communicate data successfully.

Modern fiber cables can contain up to a thousand fibers in a single cable, with potential bandwidth in terabytes per second. In some cases, only a small fraction of the fibers in a cable may be actually “lit”. Companies can lease or sell the unused fiber to other providers who are looking for service in or through an area. Companies may “overbuild” their networks for the specific purpose of having a large network of dark fiber for sale, reducing the overall need for trenching and municipal permitting.

Optical fibers are inherently very strong, but the strength is drastically reduced by unavoidable microscopic surface flaws inherent in the manufacturing process. The initial fiber strength, as well as its change with time, must be considered relative to the stress imposed on the fiber during handling, cabling, and installation for a given set of environmental conditions. There are three basic scenarios that can lead to strength degradation and failure by inducing flaw growth: dynamic fatigue, static fatigues, and zero-stress aging.

Sources – How stuff works and wikipedia




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