Light, like radio, consists of electromagnetic waves. The major difference between the two is that light waves are much shorter than radio waves. The use of electromagnetic waves for long-distance communications was the beginning of an industry known first as wireless and later as radio. This industry was the foundation for electronics, which brought the world so many fascinating technologies.

When electronic circuits replaced the mechanical components in computers, the electronics were so fast compared to the older mechanical methods that no one ever thought the speed of the calculations would be limited by the speed of electrical signals. When engineers demanded even faster electronic circuits, the very short pulses and the tiny dimensions of their integrated circuits begged for the use of light energy rather than electrical energy. The use of light signals rather than electrical signals allowed for the design of very small and...