Even with more efficient transmission techniques, the phone networks needed more capacity. Today, fiber optics are at the heart of all the long-distance networks and much of the local ones, both for telephone and cable TV service. They are the arteries that gather communications signals pumped to and from widespread homes and businesses, whether it be a phone call from San Jose to Chicago, a burst of withdrawal and deposit data on a private line between bank branches in New York and Miami or a Web page downloaded from a site in Denver to a computer in Dallas. And the number of fibers deployed continues to grow as upstart communications companies build networks from scratch. Wired for success Glass strands have many advantages over their copper and coaxial-cable counterparts.
Fiber optics are more compact, can transmit a signal farther and are less subject to interference.
Their lasers can transmit much more information per second through glass than a radio wave can through copper or air. Most important, the capacity of fiber optics is increasing rapidly, thanks to two techniques that enable the lasers to cram more information down each strand. First, the speed of the pulses is increasing. The faster the pulse, the more information conveyed. Second, researchers have developed ways to send different colors of infrared light simultaneously down a single strand, with each color pulsing out its own code.