Optical fibers are ultra-thin strands of pure spun glass, as thin as a human hair. They are bundled together into optical cables and used to send light signals over very long distances.
The thin glass center of the fiber where the light travels is called the core. It is surrounded by a material that reflects the light back into the core. Called the "cladding," this material is covered with a plastic coating that protects the fiber from damage and moisture. The entire cable is contained in a covering called the jacket.
How does an optical fiber transmit light? Light travels in a straight line, so it can't turn a corner. But if you place a mirror at the bend, it will reflect light around the corner. If there are several bends in, say, a long hallway, lining the walls with mirrors would cause the light to bounce from side to side. That's what happens inside an optical fiber. The core is like the hallway, and the cladding is like the mirrors. Light is constantly bouncing off the cladding, and since it is made from a material that doesn't absorb light, the light wave can travel long distances before the signal degrades.
These fibers are a key component in a fiber-optic relay system. The transmitter encodes data onto a light signal, and the optical fiber sends that signal. A receiver then decodes the light signal.
The Optical Society of America contributed to the scientific content in the TV portion of this report.