How Fiber Optics Are Made

The earliest engineers have been drawing glass into fibers since Roman times. It wasn’t until the 1790s that the first optical telegraph was created by the Chappe brothers, who developed a series of lights mounted on towers that relayed messages from one tower to the next. Further incarnations were steadily introduced through the mid-1800s, as scientists proved that light signals could be bent by sending a light through a curved stream of water. Thanks to initial discoveries by the famed Alexander Graham Bell, in the 1970s and 1980s, the widespread use of fibers for communications infrastructure was adopted. Today, after years of development, optical fiber systems are even more robust and powerful than ever before.

When we picture glass, the first thing that comes to mind is a transparent glass window. However, as glass gets thicker, the number of impurities increase and it becomes more clouded. Optical fibers do not measure much larger than a human hair- around 1/8mm or 0.005 inches in diameter, ensuring the clearest glass possible. Some fiber optics companies report that if you stood on an ocean made of fiber optic glass miles deep, you could see the bottom.

A fiber optic cable starts out as a large glass tube. This is first cleaned in a corrosive bath to ensure that any dirt and oil residue are removed from the tube. The preform blank is manufactured through modified chemical vapor deposition (MCVD). A solution of silicon chloride and germanium chloride is pumped with oxygen, and the gas vapor byproduct is collected in a synthetic tube. As the tube is rotated, a torch heats the outside, causing the silicone and germanium to react with the oxygen, and fuse together to form glass. It is vital that the lathe be turned uniformly for a consistent coating. The intense heat eventually causes the tube to collapse on itself and become a solid rod, transforming into the initial structure of the optical fiber.

After creating the blank, it vertically installed into a fiber drawing tower. The extreme heat of the furnace in the tower (about 2200 degrees Celsius) melts the blank until it drips and falls downward like molasses dripping from a spoon, cooling on the way and forming a thread. A large glob is attached to the end of the glass fiber, stretching and pulling it even further to the ideal thickness. A series of pulleys measure the tension on the fiber as it is being drawn. Then the fiber passes through UV lamps that bake on a protective coating to protect against dust and other contaminants.

Each fiber cable must be tested for a variety of factors, including tensile strength, refractive index profile, operating temperature, and attenuation. Finally, the fiber is rolled onto a drum, and either shipped out as is, or inserted into a cable. They can then be distributed to telephone companies, network providers, or distributors like SanSpot.