We all know that the main function of a fiber optic cables is to send a signal across significant distances and that the transmission of data is in the form of light. Everything happens at high speeds and without any interference with any other electronic devices. But how does it really-really work?

The cables contain thin strands of glass, aka fiber optics which form their core and enable the process of signal transmission. The optical signal is created with the help of a transmitter. The signal is sent through the fiber, ensuring that the signal is not lowered nor distorted. Once the signal is received it’s converted into an electrical signal.

Craig Freudenrich from  howstuffworks.com  made a really interesting analogy that will help anyone understand and visualise how the fiber optic transmission of data happens.

Suppose you want to shine a flashlight beam down a long, straight hallway. Just point the beam straight down the hallway — light travels in straight lines, so it is no problem. What if the hallway has a bend in it? You could place a mirror at the bend to reflect the light beam around the corner. What if the hallway is very winding with multiple bends? You might line the walls with mirrors and angle the beam so that it bounces from side-to-side all along the hallway. This is exactly what happens in an optical fiber.


Well, that’s exactly how fiber optics work. We are talking here about the total internal reflection. The light impulses  travel through the core (keeping in mind Freudenrich example, we can imagine we are talking about the hallway) by constantly bouncing from the cladding (the mirrors on the walls in the above example). The cladding does not absorb any light and this allows its transmission on longer distances. Even so, some of the light signals degrade within the fiber, mostly due to impurities in the glass. The extent that the signal degrades depends on the purity of the glass and the wavelength of the transmitted light (for example, 850 nm = 60 to 75 %/km; 1,300 nm = 50 to 60 %t/km; 1,550 nm is greater than 50 %/km).

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