Optical networking

Optical networking, as embodied by dense wavelength division multiplexing (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 of reconfigurable wavelength add/drop and other optical network elements (NEs), as well as cost reduction of optical amplifiers and laser devices, are pushing the revolution into the local and metropolitan networks. 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 transported and routed optically without resorting to time division multiplexing (TDM). In this paper, we describe the latest advances in optical NEs and applications in the public and private networks. In addition, we discuss how optical networking creates flexibility in sharing existing 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 systems cannot meet. Finally, we discuss future directions and optical layer restoration as a prime target of network evolution.