Tutorial overview: Multigigabit optical networking

Abstract

What is multigigabit optical networking? This is a term we are using loosely to refer to the networks with multiple gigabit data channels in order to distinguish them from networks whose aggregate bit rate is on the order of 1 Gbit/s. Current computer networks, such as Ethernet, FDDI and DQDB, suffer from lack of concurrency: at a given time, only a small number (typically one) of computers can transmit new information into the network. Therefore, each computer has to operate at the network aggregate speed, although effectively it has access only to a fraction of that bandwidth. To achieve gigabits/sec throughput, the next generation of computer networks will have to provide multiple high-speed concurrent channels to the nodes. One way to achieve concurrency is to use electronic switching, thereby placing the burden on the switch rather than each computer. Another direction is to place the burden on the optical hardware. Optical transport facilities have been recognized as an excellent choice for gigabits/sec networks due to the high bandwidths and long distances that can be reached. Moreover, WDM optical techniques allow multiple concurrent channels to be created in the same fiber, and with tunable transceivers one can potentially create networks whose topology changes dynamically in response to changing traffic patterns. In this paper, we will review a few current implementations of very high-speed networks as a background context, and then describe several prototype optical networks.