Optical fibers transmit light accurately. Optical fibers are small fibers of glass that guide light through them when light enters one end. The fibers must be pure in order to transmit light accurately. Ordinary glass is not pure enough. A three foot bar of ordinary glass would block most light. If the ocean was as pure as optical fibers need to be, then we could see through the Pacific Ocean to the Marianas Trench, over 32,000 feet deep.
To make pure glass, intense heat and pressure are required. Temperatures hot enough to melt iron are needed. Preforms, pure glass rods about the size and length of broomsticks, are used in making fibers. Pure ingredients are needed to make pure preforms. Platinum crucibles and stirring rods are used to make the preforms so the glass does not become contaminated. These are made by heating glass to 1600? C, and then to 2000? C. These preforms are carefully inspected, and if they fail, they are discarded. The inspected preforms are heated to 2200? C and the preform is drawn through a small hole drilled in a diamond by a laser. This results in the core fiber. The cladding is put on at the same time the core is being drawn through the hole. The cladding is a glass coating of slightly different composition. The fibers are tested to be able to withstand more than they will be required to in normal use. After inspection, a layer of black plastic is put on the fiber to protect it.
The difference between the core fiber and the glass cladding bends (refracts) the light through the fiber. This guides the light through the fiber, and keeps light from becoming lost. The ends of the fiber need to be smooth, so they do not scatter the light when it enters or leaves the fiber.
The repeaters on long copper cables make the signal louder when they start to fade, but they also make background noise louder. This makes them noisy and less accurate. Optical fibers send their signals as either 0?s or 1?s (light, or no light). This method enables optical fiber repeaters to make a new clear signal that is as pure as the original, making them quiet and much more accurate. If a optical fiber repeater gets a little light, it knows to make a new burst of full light. If it does not get any light, it does not send any light. Because of the fiber's binary (on-off) system, fibers can send data faster without making errors.Using normal telephone cables, the Bible could be transmitted in about an hour. Today, however, optical fibers can transmit the Bible 4 times in a second. A single 4.5 pound spool of optical fiber can carry as much data as 200 reels of copper wire weighing over 8 tons. A double thread fiber the size of a hair can transmit the same number of telephone conversations as a 512 wire copper cable as thick as your arm.
Lasers are used to give light to fibers because they can be pulsed faster than other light sources. Lasers are also needed because their light is single frequency, and high-performance fibers are designed to guide only a certain frequency of light.
Optical fibers can be used to see into places that are otherwise inaccessible. A bundle of fibers fused together can be used as a picture guide. One can look into on end of the bundle and probe the other end of the bundle into an inaccessible place, and see inside it. This technique is used to service aircraft and diagnose diseases. Fibers are now designed to be able to use newer technologies without being dug up and replaced.