How do you make the optical fibre?

By Mohd Aktar on Friday, 1 February 2013


how to make fibre optic cable


The optical fibre is the material that forms the basis of modern telecommunications networks with high capacity. An optical fibre is a very long glass filament, so fine that it is quite flexible, duly protected by a plastic sleeve. Through these, beams are transmitted through a coupled laser and light signals are detected at the destination.

Evidently, to have a great capacity for long-distance transmission, the fibre must have very particular characteristics that involve a high-tech process in manufacturing the optical fibre. Consider that the standard thickness of the fibre is 125 microns (about twice that of a human hair) and the core is about 8 microns (in single mode fibres, which are used for long distance communications) which is obviously critical to maintain the purity and consistency of the core.

All this makes the manufacturing of fibre, a complicated process. However, the rationale is simple (and it is a brilliant idea). The glass tubes are built on large macroscopic scale reproducing the structure of the fibre. These tubes are called preforms. Subsequently, the preform is stretched until they are melted and obtained a fine diameter elongate filament whose microscopic scale reproduces the original preform.

The manufacturing process of the preform is not at all easy because of its very specific characteristics and extreme purity.

In this process, part of hollow glass rods is bathed in a gas containing particles which will be the future core. By making this warm up to thousand degrees, these particles begin to melt until the hollow tube collapses and forms a solid rod with the desired structure: the preform.

Once made, preforms are placed vertically and are heated until they are melted forming a continuous trickle. These are drawn from a preform fibre miles and miles. In this process, despite of the simplicity of the idea, it is very complex and delicate, because you have to ensure that the flow remains constant i.e., that the thread maintains a thickness of 125 microns and there are no undue stresses. Also, this phase is used to create a protective layer on the glass.

This optical fibre is wound onto large reels. These large communications networks using multiple fibre bundles are grouped into a cable as thick as a power cable but capable of transmitting a much larger amount of information for greater distances and with less spending power.

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