Fiber Optics

Optical fibers are fabricated in a multi-step process: preform fabrication, fiber drawing, fiber coating, and spooling. A preform is a giant-sized version of the final fiber, with central core and cladding refractive indices equal to those of desired product. Preform diameters are typically 0.4-1 in (1-2.5 cm). They are produced by one of several variations on chemical vapor Figure 2. Illustration by Hans & Cassidy. Courtesy of Gale Group.
deposition, in which chemicals (primarily silica, with other exotic compounds) are vaporized and allowed to deposit on a tube or rod. The porous form produced is heated to release trapped gases and water vapor that might otherwise compromise the performance of the final fiber.

In the drawing stage, the end of the preform is lowered into a furnace heated to roughly 3,632°F (2,000°C). The tip softens until it is drawn down by gravity, shrinking in diameter. Sensors constantly monitor the fiber diameter and concentricity to assure optimal results. An acrylic coating is applied to protect the fiber from damage and preserve its strength. Finally, it is wound onto a takeup spool.