Fiber optics (or optical fibers) are long, thin strands of very pure glass about the diameter of a human hair. They are used to transmit light signals over long distances. The advantage of fiber optics over other types of communication systems is that they can carry much more information than electrical cables and they are not affected by electromagnetic interference.
The first practical use of fiber optics was in 1854 when French physicist Claude Chappe used them to send telegraph messages between Paris and Lille. In 1880, Alexander Graham Bell demonstrated that light could be used to transmit speech, and in 1910,optical fibers were used for medical examinations.
During World War II, research into fiber optics was motivated by the need for secure communications; the German enigma machine encrypted voice transmissions so that they could not be understood if intercepted. In 1966, Charles Kao proposed using glass fibers for telecommunications; his work led to the development of optical fiber cables that could carry extremely high-quality signals over long distances with very little loss.
Today, fiber optic cables are used extensively in long-distance telephone lines, cable television networks, and computer networks including the Internet. They are also being used increasingly in local area networks and even within buildings where their immunity to electromagnetic interference makes them ideal for carrying sensitive data such as video conferencing and medical images.