OPTICAL NETWORKING

Optical networking, as embodied by dense wavelength division multiplex ing (DWDM) and optical amplification, has revolutionized long-distance transport and has resulted in capacity expansion, cost reduction, and operations simplification. Extension to more wavelengths, emergence o f reconfigurable wavelength add/drop and other optical network element s (NEs), as well as cost reduction of optical amplifiers and laser dev ices, are pushing the revolution into the local and metropolitan netwo rks. Traffic generated in any format, such as SONET/SDH, asynchronous transfer mode (ATM), and plesiochronous digital hierarchy (PDH), with bit rates ranging from 45 Mb/s to 10 Gb/s, can be economically transpo rted and routed optically without resorting to time division multiplex ing (TDM). In this paper, we describe the latest advances in optical N Es and applications in the public and private networks. In addition, w e discuss how optical networking creates flexibility in sharing existi ng fiber inventory between service providers. We present an example of how optical networking is capable of meeting the emerging demand for high-capacity clear-channel end-user services, a demand that TDM syste ms cannot meet. Finally, we discuss future directions and optical laye r restoration as a prime target of network evolution.