ABSTRACT
The focus of this chapter is to present technological advances, promising architectures, and exciting research issues in designing and operating next-generation optical wavelength-division multiplexing (WDM) networks, which are scalable and flexible. We discuss important building blocks of optical WDM networks and overview access, metropolitan, and long-haul networks separately. Special attention has been paid to the long-haul network because there is a tremendous need to develop new intelligent algorithms and approaches to efficiently design and operate these wide-area-optical-mesh networks built on new emerging technologies. We present several research topics including routing and wavelength assignment, fault management, multicasting, traffic grooming, optical packet switching, and various connection-management problems. The Internet is developing rapidly with the ultimate goal being to provide us with easy and fast access to any desired information from any corner of the world. Information exchange (or telecommunications) technology, which has been evolving continuously since the telephone was invented, is still striving to meet the users’ demands for higher bandwidth. This demand is attributed to the growing popularity of bandwidth-intensive
* This work has been supported in part by the U.S. National Science Foundation Grant No. ANI-98-05285. Aysegül Gençata was a visiting scholar at U.C.Davis when this work wasperformed
networking applications, such as data browsing on the World Wide Web (WWW), Java applications, video conferencing, interactive distance learning, on-line games, etc. Figure 1.1 plots the past and projected growth of data and voice traffic as reported by most telecom carriers. 1 It shows that, while voice traffic continues to experience a healthy growth of approximately 7% per year, data traffic has been growing much faster. To support this exponential growth in the user data traffic, there is a strong need for highbandwidth network facilities, whose capabilities are much beyond those of current highspeed networks such as asynchronous transfer mode (ATM), SONET/SDH* etc. 2
Fiber-optic technology can meet the previously mentioned need because of its potentially limitless capabilities: 3 huge bandwidth (nearly 50 terabits per second [Tbps] for single-mode fiber), low signal attenuation (as low as 0.2 dB/km), low signal distortion, low power requirement, low material usage, small space requirement, and low cost. Given that a single-mode
WDM is a favorite multiplexing technology in optical communication networks
because it supports a cost-effective method to provide concurrency among multiple transmissions in the wavelength domain. Several communication channels, each carried by a different wavelength, are multiplexed into a single fiber strand at one end and demultiplexed at the other end, thereby enabling multiple simultaneous transmissions. Each communication channel (wavelength) can operate at any electronic processing speed (e.g., OC-192 or OC-768).* For example, a fiber strand that supports 160 communication channels (i.e., 160 wavelengths, each operating at 40 Gbps) would yield an aggregate capacity of 6.4 Tbps.
