Note: Many topics at this site are reduced versions of the text in "The Encyclopedia of Networking and Telecommunications." Search results will not be as extensive as a search of the book's CD-ROM.

An optical network is a network in which the physical layer technology is fiber-optic cable. Cable trunks are interconnected with optical cross-connects (OXCs), and signals are added and dropped at optical add/drop multiplexers (OADMs). The holy grail is an all-optical network. In this scheme, an optical wavelength (which acts like a data circuit) stays in the optical realm from end to end.

In contrast, most optical networks have implemented OEO (optical-electrical-optical) switches, which convert optical signals to electrical signals for processing, and then back again to optical signals for the next leg of the trip. The optical-to-electrical conversion adds delay and introduces possible errors as the signals are converted, moved up the protocol stack, and processed by software or firmware. The all-optical network avoids this process. At this writing, components that make the all-optical network a reality are emerging. These are discussed next.

This topic continues in "The Encyclopedia of Networking and Telecommunications" with a discussion of the following:

• WDM (wavelength division multiplexing) and DWDM (dense wavelength division multiplexing) systems
• Lambda (infrared wavelength circuits)
• SONET/SDH optical networking standards
• Internet architecture and optical network cores
• All-optical network components
• Feeder networks such as SONET, cable networks, PONs (passive optical networks), and wireless networks
• OXC (optical cross-connects)-- optical switches
• Waveguide switches using bubbles, thermo-optic switching, or liquid crystals
• Optical network control plane
• MPLS (Multiprotocol Label Switching)
• LSRs (label switching routers)
• Multiprotocol Lambda Switching
• Generalized MPLS or GMPLS
• Sycamore's ODSI (Optical Domain Service Interconnect)

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