Fiber-Optic Cable

In almost every way, fiber-optic cable is the ideal cable for data transmission. Not only does this type of cable accommodate extremely high bandwidths, but it also presents no problems with EMI and supports durable cables and cable runs as long as several kilometers. The two disadvantages of fiber-optic cable, however, are cost and  

installation dificulty. Despite these disadvantages, fiber-optic cable is now often installed into buildings by telephone companies as the cable of choice. The center conductor of a ?ber-optic cable is a ?ber that consists of

highly refined glass or plastic designed to transmit light signals with little loss. A glass core supports a longer cabling distance, but a plastic core is typically easier to work with. The ?ber is coated with a cladding or a gel that re?ects signals back into the fiber to reduce signal loss. A plastic sheath protects the fiber (see Figure. A fiber-optic network cable consists of two strands separately enclosed in plastic sheaths. One strand sends and the other receives.

Two types of cable con?gurations are available: loose and tight configurations. Loose con?gurations incorporate a space between the fiber sheath and the outer plastic encasement; this space is filled with a gel or other material. Tight configurations contain strength wires between the conductor and the outer plastic encasement. In both cases, the plastic encasement must supply the strength of the cable, while the gel layer or strength wires protect the delicate fiber from mechanical damage. Optical fiber cables don't transmit electrical signals. Instead, the data signals must be converted into light signals. Light sources include lasers and light-emitting diodes (LEDs). LEDs are inexpensive but produce a fairly poor quality of light suitable for only less-stringent applications. The end of the cable that receives the light signal must convert the signal back to an electrical form. Several types of solid-state components can perform this service. One of the signi?cant dificulties of installing ?ber-optic cable arises when two cables must be joined. The small cores of the two cables

(some are as small as 8.3 microns) must be lined up with extreme precision to prevent excessive signal loss.