le think about the wide bandwidth of optical fiber. Although this is certainly important and provides the primary reason for many organi- zations migrating to optical transmission systems, it is not the only rea- son for considering the use of this type of transmission system. As we will note shortly, there are a number of reasons, some of which may be more applicable to one type of organization than to another type. Team-Fly® Introduction Table 1.2 lists seven key advantages associated with the use of a fiber- optic transmission system. Because many persons associate bandwidth primarily with optical fiber, let's first discuss this topic. Bandwidth As noted earlier, most persons rightly consider the wide bandwidth of optical fiber as the key advantage associated with an optical transmis- sion system. Because the information transmission capacity of a com- munications system is directly proportional to bandwidth, the high fre- quency of light makes it possible to transmit data at extremely high rates. While gigabit data transmission rates are a common capability on optical fiber, research indicates that operating rates up to and beyond 1014 bits/s can be achieved on fiber-optic transmission systems. When compared to the 56-kbit/s rate on the public switched telephone network (PSTN) and the approximate 1-Mbit/s rate supported by an asymmetri- cal digital subscriber line (ADSL), it is easy to visualize how optical fiber provides many magnitudes of capacity enhancement over conventional copper cable. This explains why a thin glass fiber can easily transmit hundreds of thousands to millions of telephone conversations simulta- neously. While this is certainly a valid reason for communications carri- ers migrating their backbone infrastructure to optical fiber, it also pro- vides the rationale for the use of fiber in numerous other applications. TABLE 1.2 Large bandwidth permits high data transmission, which also supports the aggregation of voice, video, and data Advantages of Fiber-Optic Trans- Technological improvemen