Optical fiber transmits data as light along a thin glass or plastic filament. The nature of how light refracts in glass or plastic allows this. You may have seen tabletop novelty lights that use plastic filaments. These have ordinary lightbulbs in the base, but sticking out of the base are a number of plastic strands looking something like a porcupine. The ends of these strands glow the same color as the lightbulb.
The strands guide the light from one end to the other. Optical fiber works the same way. At one end of the fiber is a light source, and at the other end there's a light detector. To transmit binary data, the light can be turned on for each 1 and off for each 0.
The light source in less expensive systems is a light-emitting diode, something like the light on some keyboards that indicates whether the "Caps Lock" is on. More expensive optical fiber systems have a laser as a light source. The laser is better because it produces a tightly focused beam.
Optical fiber has a number of major advantages over copper wire technology. First, because it uses light and not electricity, optical fiber is immune to electromagnetic interference. Second, it has a much higher bandwidth than copper wire. Third, it can run much longer distances than copper wire. While repeaters may still be needed, they can be spaced much farther apart.
Optical fiber does have some disadvantages, though. The main issue is cost. The fiber itself is more expensive to make than a wire, and the equipment needed at both ends of a connection is more expensive too. Also, optical fiber is much harder to work with. It is fairly stiff and a lot easier to accidentally damage. A network technician cannot simply splice two fibers together the way two wires can be spliced.
Because of these disadvantages, optical fiber is often used for a backbone, which is a term for a major pathway in a network. For example, if a company has 100 nodes split evenly between two adjacent office buildings, the connection between two buildings might be optical fiber, while the connections within each building could be copper wire.
The backbone would be optical fiber because it gets more traffic than any other connection. But connecting all the computers in each office building through optical fiber would be expensive and unnecessary.
Wireless refers to transmitting data via electromagnetic waves through the air. These waves are categorized based on their frequency. Lower frequency waves are called radio waves; these include the frequencies used by AM and FM radio as well as those used by broadcast television. Higher frequency waves are called microwaves.
Wireless technology is not a general replacement for wires or fiber. Any time wire or fiber is practical, it is a better choice than wireless, which is used in special situations like long distance transmission. In fact, the long distance telephone network relies on microwave transmission towers.
Another situation is broadcasting, which refers to sending out a single message to multiple receivers at once. Unlike wires and fiber, which direct a signal to a particular destination, wireless transmissions are unguided. They may be aimed in a specific direction, but they are still broadcast to a wide area. The advantage is that any receivers in the broadcast area can get the message. This approach is more efficient than sending the same message to each receiver individually.
A final reason to use wireless is mobility. In a wired network, nodes can only be where the wires are. In a wireless network, the nodes can be anywhere in the transmission area. Wireless has a couple of problems that the other media do not. One problem is that air is the conduit for the transmission, and the characteristics of the air are constantly changing.
For example, weather, solar flares, and other natural phenomena more often affect wireless networks. The other problem relates to security. Because the messages are broadcast, they are easily intercepted. This makes the security built into the protocol especially important.
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02132011
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