Inter-exchange carrier (IXCs) systems are a combination telecommunications networks that connect local exchange carriers (LECs), competitive local exchange carriers (CLECs), local post, or telephone and telegraph (PTT) with each other. IXCs provide long distance bearer service communication and may provide other value-added teleservices. IXC s are regulated by governmental commissions but are not usually government-owned. In other parts of the world the government may own and operate LECs and PTTs.

In order to provide the bandwidth necessary to carry the volume of long-distance voice and data traffic at reasonable cost, most IXCs have deployed large bundles of fiber-optic cables that interconnect their switching systems. Burying thousands of miles of fiber cable is costly. However, each pair of fibers is capable of providing many Gbps of bandwidth.

The explosion of the Internet and the demand for advanced multi-media services continues to drive the demand for increased bandwidth at low cost. To increase the capacity of fiber cables, new fiber optic technology has emerged. By utilizing a technology known as dense wavelength division multiplexing, DWDM, each fiber can carry 80 or more separate light-waves. As of 2001, some DWDM technologies were capable of providing over 1 Tbps (1,000 Gbps) of bandwidth, enough to transmit in one second the contents of 150,000 encyclopedias. Advances in optical networking equipment and light-wave amplification technologies will continue to add bandwidth the fiber networks.

Figure 9.13 shows a diagram of an inter-exchange carrier network. This diagram shows that the IXC interconnects LECs and CLECs with teach...