Technology based on the use of hair-thin, transparent fibers to transmit light or infrared signals. The fibers are flexible and consist of a core of optically transparent glass or plastic, surrounded by a glass or plastic cladding that reflects the light signals back into the core. Light signals can be modulated to carry almost any other sort of signal, including sounds, electrical signals, and computer data, and a single fiber can carry hundreds of such signals simultaneously, literally at the speed of light. Signals that have weakened after travelling very long distances in the fibers can be optically pumped with lasers, amplifying them without the need to convert them into electrical signals. Optical fibers are relatively inexpensive to manufacture and install when compared with wire cables, and they require very little power and are easily laid out underground. Optical fibers are also used to transmit images focused on one end to the other end through circuitous paths, as in bronchoscopes and colonoscopes used in medical examinations.