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Fiber optic cable design

By Steve Rogers,
The fiber optic cable provides the fiber / s inside the appropriate protection for the installation site. When we say "cable" we mean the complete assembly of the fibers, the reinforcement elements, and the jacket. Fiber optic cables are of different types, depending on the number of fibers, the model and the place of installation. It is important to choose the cable carefully as that will determine the ease with which the installation will be done, the splicing or termination of the cable, the cost of the cable and the duration in the field.
The function of the cable is to protect the fibers from the effects of the environment in the place where they are installed. Outdoors, it depends on whether the cable is directly buried, inserted into underground conduits, suspended in the air or even installed underwater. Will the cable get wet or wet? Should it withstand high tensile stress when installing in underground ducts, or continuous tension when installed suspended in the air? Will it be exposed to chemicals or should it withstand a wide range of temperatures? What happens if he is chewed by a squirrel, beaver or another rodent? Indoor,

Cable construction
All cables are composed of several layers of protection for the fibers. In principle, most of the cables have a standard fiber with a primary buffer coating of 250 microns in diameter and then add:

Adjusting “structure” buffer coating (for tight structure cables such as simplex cables, zip cord duplexes, distribution cables, and breakouts )
A soft, 900-micron outer diameter protective coating that is applied directly to the 250-micron coating to provide additional protection to the fiber and allow easier handling and direct termination when applying a connector to the fiber.

Baggy structure tubes (baggy structure cables)
They are thin and small plastic tubes that contain up to twelve fibers, which have a coating of 250 microns; They are used to protect the fibers in the cables intended for use in an external plant. These tubes allow the fibers to remain insulated from high tension and can be filled with components that block water (gel, tape or absorbent powder) to prevent moisture from entering.

Reinforcement elements
The reinforcement elements that are usually used are aramid threads, the same ones that are used in bulletproof vests, usually known through the Dupont trademark, Kevlar, which absorb the tension produced by applying a tensile force on the cable and provide cushioning to the fibers. Aramid fibers are not only used because they are strong, but also because they do not stretch. If you pull hard on them, they will not stretch but may break if the tension exceeds its limits. This ensures that the reinforcement elements do not stretch and relax and, thus, the fibers are held together within the cable.
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Some cables also include a central fiberglass rod that provides greater strength and tensions the cable in order to prevent the fibers from twisting and being damaged. If included, the rod must be attached to swivel links, to apply the tensile force on the fiber, and to clamps on the splice closures and on the connection panels, for splicing or termination. At present, very few cables use metal reinforcement elements because it is necessary to connect the cables to a proper grounding, which makes installation difficult.

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