Overview

The telephone industry has been busy converting its existing outside copper plant to newer fiber optics. There are many advantages to using fiber rather than copper. Higher bandwidth is the foremost advantage; quieter communications is another. There are a number of other economical advantages to using fiber optics.

In the existing copper infrastructure, amplifiers are required at regular intervals. These amplifiers are placed in cabinets in various locations (outside large subdivisions, along highways). The amplifiers are analog devices, unless recently upgraded to support newer digital services (such as ISDN). The problem many telephone companies encounter when offering new services is in upgrading existing equipment (including these amplifiers and also multiplexers) to support the newer digital services.

With fiber optics, there are no amplifiers, only repeaters. The repeaters can be placed at greater distances from the central office and are easier to upgrade when necessary. If a fiber optic cable is cut, service can often be switched to another backup fiber. This of course depends on the network configuration. Most fiber optic operators are deploying SONET rings, which provide a self-healing network. Another advantage of SONET is its standard multiplexing format, capable of carrying DS1 transmissions or even DS3. SONET itself is a standard for fiber optics transmissions, making interconnection with other equipment easier. SONET also uses a flexible architecture, allowing for future growth.

One of the unique advantages of SONET is its ability to access a single transmission frame without demultiplexing the entire transmission. This is not...