#Glass preform how to

The different vapor deposition methods differ in many respects, e.g. as fuel gas), the water content of such preforms is very low, avoiding a strong loss peak at 1.4 μm, which would also affect the telecom bands (→ optical fiber communications). Particularly when no hydrogen is present (e.g. In particular, SiCl 4 and GeCl 4 are easily purified by distillation, as they are liquid at room temperature. The general advantage of vapor deposition methods is that extremely low propagation losses down to below 0.2 dB/km can be achieved because very high-purity materials can be used and contamination is avoided. There is also plasma-enhanced chemical vapor deposition (PECVD), operating at atmospheric pressure with fairly high deposition rate. The deposition is slow, but very precise.Ī modified method with particularly high precision is plasma impulse chemical vapor deposition (PICVD), where short microwave pulses are used. The difference to MCVD is that microwaves instead of a burner are used for heating the deposition region. Instead of conventional MCVD, one can use plasma activated chemical vapor deposition (PCVD). The process results in a fully dense and very clear glass. During that viscous sintering, the preform is held in a gas atmosphere, which can be oxidizing or reducing, and influences the deviation from perfect stoichiometry. combustion of hydrogen) produce a fine white “soot” of (often doped) silica which is deposited on the preform and later on sintered into a clear glass layer at ≈1500 ☌. germanium tetrachloride (GeCl 4) and rare earth dopants → fiber core) is generated, and chemical reactions in the gas (e.g. Here, a mixture of oxygen, silicon tetrachloride (SiCl 4) and possibly other substances (e.g. This method was developed for silica telecom fibers in the 1970s, with pioneering contributions from the University of Southampton (UK), Bell Telephone Laboratories (Bell Labs), and Corning. Many fiber preforms are fabricated with a process called modified chemical vapor deposition (MCVD or just CVD). Vapor Deposition Methods Different variants of deposition processes are used. In this section, the fabrication of standard fiber preforms is explained, while special preforms for various types of specialty fibers are discussed later on. Here, we cover only the fabrication of glass preforms, and mostly on those for silica fibers. Also, some companies offer to apply the cladding glass to received core rods. However, there are also suppliers of various kinds of fiber preforms, which are then to be drawn into fibers elsewhere. In most cases, the fiber preforms are fabricated on the same sites where the fiber drawing tower is operated. Plastic optical fibers can be drawn from preforms in a similar process as often used for silica fibers, only with a much lower temperature (e.g. In particular, this holds for the refractive index profile, including the structure made for the fiber core. The drawn fiber has a much smaller diameter than the preform, and all features of the preform are getting correspondingly smaller in the fiber. The article on fiber fabrication describes the drawing process and details of the used drawing towers. 40 cm long and have a diameter of a couple of centimeters, but there are also much longer preforms and some with a large diameter of e.g.

#Glass preform how to

How to cite the article suggest additional literatureĪ fiber preform is a typically cylindrical piece of optical glass which is used for drawing an optical fiber in a fiber drawing tower.

Definition: a piece of glass from which an optical fiber can be drawn