Overview

In this chapter, we study optical networks that are capable of providing packet-switched service at the optical layer. We call these networks photonic packet-switched (PPS) networks. Packet-switched services are provided today using electronic switches by many networks, such as IP and ATM networks. Here, we are interested in networks where the packet-switching functions are performed optically. The goal of PPS networks is to provide the same services that electronic packet-switched networks provide, but at much higher speeds.

The optical networks that we have studied so far provide circuit-switched services. These networks provide lightpaths, which can be established and taken down as needed. In these networks, the optical nodes do not switch signals on a packet-by-packet basis, but rather only switch at the time a circuit is established or taken down. Packet switching is done in the electronic domain by other equipment such as IP routers or ATM switches. These routers and ATM switches make use of lightpaths provided by the optical layer to establish links between themselves as needed. In addition to switching packets, routers and ATM switches make use of sophisticated software and hardware to perform the control functions needed in a packet-switched network.

We will see in this chapter that all the building blocks needed for optical packet switching are in a fairly rudimentary state today and exist only in research laboratories-they are either difficult to realize, very bulky, or very expensive, even after a decade of research in this area. Moreover, it is likely that we...