...
Today Three methods are used to manufacture perform.
...
Modified Chemical Vapor Deposition(MCVD)
...
First, a cylindrical preform is made by depositing layers of specially formulated silicon dioxide on the inside surface of a hollow substrate rod. The layers are deposited by applying a gaseous stream of pure oxygen to the substrate rod. Various chemical vapors, such as silicon tetrachloride (SiCl 4 ), germanium tetrachloride (GeCl 4 ), and phosphorous oxychloride (POCl 3 ), are added to the stream of oxygen. As the oxygen contacts the hot surface of the rod-a flame underneath the rod keeps the walls of the rod very hot-silicon dioxide of high purity is formed. The result is a glassy soot, several layers thick, deposited inside the rod. This soot will become the core. The properties of these layers of soot can be altered depending on the types of chemical vapors used.
Fig.Illustration of the modified chemical vapor deposition (inside) process
After sufficient layers are built up, the tube is collapsed into a solid glass rod referred to as a preform. It is now a scale model of the desired fiber, but much shorter and thicker. The preform is then taken to the drawing tower, where it is pulled into a length of fiber up to 10 kilometers long.
Drawing the Fiber
...
Refrences
...
http://www.thefoa.org/tech/fibr-mfg.html
...