696 Photonic Packet Switching Summary Photonic packet-switched networks offer the potential of realizing packet-switched networks with much higher capacities than may be possible with electronic packet-switched networks. However, significant advances in technology are needed to make them practical, and there are some significant roadblocks to overcome. The state of optical packet-switching technology is somewhat analogous to the state of electronic circuits before the integrated circuit was invented. All the building blocks needed for optical packet switching are in a fairly rudimentary state today and in re- search laboratories; they are either difficult to realize, very bulky, or very expensive. For example, optical buffering is implemented using hundreds of meters of delay lines, which are bulky and can only provide limited amounts of storage. Transmit- ting data at 100 Gb/s and higher line rates over any significant distances of optical fiber is still a major challenge. At this time, fast optical switches have relatively high losses, including polarization-dependent losses, and are not amenable to integration, which is essential to realize large switches. Optical wavelength converters, which have been proposed for many of the architectures, are still in their infancy today. Temperature dependence of individual components can also be a significant problem when multiplexing, demultiplexing, or synchronizing signals at such high bit rates.