Preform process in optical fiber

Preform process in optical fiber:

Standard optical fibers are created by first fabricating large-diameter «preforms» with a carefully controlled refractive index profile, and then «stretching» the preforms to form longer, thinner optical fibers. Preforms are typically made by three chemical vapor deposition methods: inside vapor deposition, outside vapor deposition, and vapor axial deposition. The process of preform starts as the hollow glass tube whose length is approximately which is placed horizontally and it is rotated slowly on a lathe with the inside vapor deposition. Gases such as germanium tetrachloride (GeCl4) or silicon tetrachloride (SiCl4) are injected along with oxygen at the end of the tube. Optical products manufacturer uses precision optical polarizers in laser line beam splitter manufacturing process.

It’s process

An external hydrogen burner is used to heat the gases. A temperature of up to 1,900 K (1,600 °C, 3,000 °F) is maintained to heat up the gases where the tetrachlorides start reacting with the oxygen in order to produce Germania or silica particles. When the reaction conditions are chosen to allow this reaction to occur in the gas phase throughout the tube volume, in contrast to previous techniques where the reaction occurs only on the surface of the glass, this technique is called modified chemical vapor deposition. The oxide particles then aggregate to form large particle chains, which then deposit as soot on the tube walls. The large difference in temperature between the gas core and the wall causes coagulation which pushes the gas particles outwards. The torch is moved up and down the length of the tube to deposit the material evenly. After the torch reaches the end of the tube, it is brought back to the beginning of the tube and the deposited particles are melted to form a solid layer.

The composition for each layer can be modified by changing the gas composition, resulting in precise control of the optical properties of the finished fiber. Glass is formed by flame hydrolysis in external vapor deposition or vapor axial deposition, a reaction in which silicon tetrachloride and germanium tetrachloride are oxidized by reaction with water (H2O) in an oxyhydrogen flame. During the process of external vapor deposition, the glass gets deposited on a solid rod, which is removed before further processing. A short lead rod is used in vapor axial deposition, and a porous preform, the length of which is not limited by the size of the source rod, is fabricated at its end.