With the explosive evolution of communication, motivated by the need to increase the capacity of voice traffic, video and high-speed data, we constantly face new concepts in technologies in terms of means of transport of information. It is in this idea that the optical fiber emerges, which ensures high level of reliability at the level of transmission of signals and data, voice and video. Fiber optic cables are replacing copper wires to increase the speed of digital information transmission. These cables are extremely pure "glass wires" bundles that were lined in two layers of reflective plastic. A light source is switched on and off quickly to one end of the digital data transmission cable. The light travels through the glass wires and continuously reflects outside the interior of the mirrored plastic coatings in a process known as internal total reflection. Fiber-optic systems can transmit billions of data bits per second, and they can even carry multiple signals along the same fiber using different color lasers. These cables are as thin as a human hair that carries digital information over large distances. The transmission of light by fiber follows a single principle, regardless of the material used or the application: a beam of light is launched at one end of the fiber and, by the optical characteristics of the medium (fiber), this beam travels through the fiber through reflections Successive. The fibre has at least two layers: the core (glass filament) and the coating (electrically insulating material). What is it? Think of a huge soda straw or a flexible plastic pipe. Imagine, for example, an excessively long barrel. Now, consider that the inner surface of this barrel was coated with a perfect mirror and this mirror was made of extremely pure glass, so that, even if it is several kilometers long, the light can still cross it (imagine glass so Transparent that, a window with this glass, several kilometers thick, still seems clear, the light crosses with the utmost sharpness possible). So, imagine you're looking at one of the ends of the barrel. Several kilometers away, at the other end, a friend of yours connects a flashlight and reflects its light inside the barrel. Once the inside of the barrel is coated with a perfect mirror, the lantern light will reflect on the surface of the barrel (even if it is curved or distorted) and you'll see it at the other end. If your friend starts to turn the flashlight on and off in the Morse code way, he will be able to communicate with you through the pipe. This is the essence of the fiber optic cable. Even confined to a physical medium, the light transmitted by the fiber optics provides the range of transmission rates (speeds) high, from the order of 109 to 1010 bits per second (about 40gbps), with low attenuation rate per kilometer. But the total transmission speed possible has not yet been achieved by existing technologies. As the light spreads inside a physical environment, still suffering the phenomenon of reflection, it fails to reach the velocity of propagation in the vacuum, which is 300,000 km/second, being this speed diminished considerably. To perform data transmission in a fiber optic, special equipment must be used that contains a photo emitter, that is, a device that can turn electrical signals into pulses of light. Thus, the pulses of light begin to represent binary digital values corresponding to the data. Source: Oficina da Net
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