How Fiber Works
Communications Network Backbone
Optical Fiber is used in place of metal wire for many reasons including its ability to carry signals over very long distances with minimal attenuation or loss. They are also immune to electromagnetic interference, unlike the metal wires they are increasingly replacing.
Used primarily as the backbone of the modern telecommunications grid, the advent of Fiber Optics allowed for universal broadband Internet access for homes and businesses around the world.
During the early days of the commercial Internet, hundreds of thousands of kilometers of fiber optic cables were laid, much of which is still not in use (known as Dark Fiber). That mass of fiber optic cable is credited with the rise of India and China as major technological powers because it allows literally thousands of individual entrepreneurs to find or create employment for themselves serving clients in other countries thousands of kilometers away.
Single and Multimode Fiber Optic Cable
Fiber optic cable works to transmit light because the hollow, round glass (or sometimes plastic) wires reflect the light back to the core of the wire, causing the cable to act as a waveguide.
Fibers that support multiple propagation paths are called Multimode Fibers (MMF). MMF cable is generally used for short distance communication or in applications where large amounts of power are required.
Fibers that support a single mode are called Single Mode Fibers. This tends to be the type of fiber optical wire used in high-speed data transfer and as the backbone of the Internet.