Optical fiber is a flexible glass strand that transmits data as light. It is thinner than a human hair. It carries pulses of light that encode data. Fiber has enormous bandwidth. It carries terabits per second over thousands of kilometers. It is immune to electromagnetic interference. It is the backbone of the internet.

Fiber works by total internal reflection. Light entering the core bounces off the cladding without escaping. It travels for miles with little loss. Lasers or LEDs generate the pulses. Photodetectors convert light back into electrical signals. Amplifiers boost the light every 50 to 100 kilometers.

Types of fiber

• Single-mode: small core, long distances, telecom
• Multi-mode: larger core, short distances, data centers
• Plastic: cheap, short runs, consumer audio
• Photonic crystal: specialty, research

Fiber replaced copper for long-haul networks. It offers higher bandwidth, lower latency, and immunity to interference. But it is fragile and expensive to install. Most homes still connect via copper or coax. Fiber to the home is growing, but unevenly. The fiber is the future. The copper is the past.