Technology
Optical Fiber Communication
Quick fact
A single optical fiber can carry tens of terabits per second—enough to stream millions of HD videos simultaneously—using pulses of laser light thinner than a human hair.
Why this is interesting
Every time you stream a video or make a long-distance call, your data races through thin strands of glass. But how does light carry information without leaking out?
Read the full explanation
Understanding Optical Fiber Communication
Optical fiber communication sends data as flashes of light through a transparent fiber. The fiber has two parts: a central core (where light travels) and an outer cladding with a lower refractive index. This difference makes light bounce off the cladding and stay inside the core—a phenomenon called total internal reflection. The light pulses represent digital 1s and 0s. At one end, a laser or LED converts electrical signals into light; at the other, a photodetector converts them back. Compared to copper wires, fibers are lighter, immune to electromagnetic interference, and can carry vastly more data over longer distances without amplification.
A deeper explanation
The key to optical fiber's efficiency is total internal reflection, which occurs when light strikes the core-cladding boundary at an angle greater than the critical angle. This confines nearly 100% of the light within the core. The core's diameter is about 8–10 micrometers for single-mode fibers, allowing only one light path and minimizing signal dispersion. For longer links, erbium-doped fiber amplifiers (EDFAs) boost signals optically without converting them to electricity. The low attenuation (around 0.2 dB/km for standard single-mode fiber at 1550 nm wavelength) enables transoceanic cables to function without repeaters for hundreds of kilometers. This combination of high bandwidth (theoretically 30 THz), low loss, and noise immunity makes optical fiber the preferred medium for backbone networks connecting continents and data centers.