The components of fiber optic cables include the core, cladding, strength members, buffer, and jacket. Some types of cable also have a copper conductor that provides power to repeaters, concentrators, and other components.
The core of the cable is made of one or more glass or plastic fibers, and it provides the pathway through which the transmitted light can flow. Plastic is more flexible than glass; consequently, plastic is cheaper and easier to manufacture, but it doesn’t work very well over long distances. The diameter of a core will measure from two to several hundred microns. A micron is about 1/25,000 of an inch. For networking considerations you should use core sizes of 60 to 100 microns. Most networking cables have two core fibers, which allow the cables to transmit in both directions at once.
The core and cladding are manufactured as a single unit. The cladding is usually made from plastic, and it provides a refractive surface. Light that strikes this surface is reflected back into the core and continues its journey. The cladding has a lower refraction index, which means that it reflects light instead of absorbing light.
The buffer consists of one or more layers of plastic. It surrounds the cladding and core. The buffer strengthens the cable and prevents damage to the core.
The strength members are strands of very tough material, such as fiberglass, steel, or Kevlar. They provide extra strength for the cable.
The jacket (which can be either plenum or nonplenum) is the outer covering or shield of the cable.
Fiber-optic cable comes in two forms: single-mode and multi-mode. Single-mode cable is so narrow that light can travel through it only in a single path. This type of cable is extremely expensive and very difficult to work with. Multi-mode cable has a wider core diameter, which gives light beams the freedom to travel several paths. Unfortunately, this multi-path configuration allows for the possibility of signal distortion at the receiving end.
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