Uses of optical fibers. Fiber optics is a branch of physics based on the transmission of light through transparent fibers of glass or plastic. These optical fibers can carry light over distances ranging from a few inches or centimeters to more than 100 miles (160 kilometers). Such fibers work individually or in bundles. Some individual fibers measure less than 0.00015 inch (0.004 millimeter) in diameter. Optical fibers have a highly transparent core of glass or plastic surrounded by a covering called a cladding. Light impulses from a laser, a light bulb, or some other source enter one end of the optical fiber. As light travels through the core, it is typically kept inside it by the cladding. The cladding is designed to bend or reflect--inward--light rays that strike its inside surface. At the other end of the fiber, a detector, such as a photosensitive device or the human eye, receives the light. Optical fibers have a number of uses. In fiber-optic communication systems, lasers transmit coded messages by flashing on and off at high speeds. The messages travel through optical fibers to interpreting devices that decode the messages, converting them back into the form of the original signal. Fiber-optic communication systems have a number of features that make them superior to systems that use traditional copper cables. For example, they have a much larger information-carrying capacity and are not subject to electrical interference. In addition, signals sent over long-distance fiber-optic cables need less amplification than do signals sent over copper cables of equal length. Many telephone and other communication companies have installed large networks of fiber-optic cables. Underwater fiber-optic cables carry signals across the Atlantic and Pacific oceans. Excerpt from the "Fiber optics" article, The World Book Encyclopedia © 1999 |