An overview of emerging all-optical networks is given. The characteristics and alternative architectures for single-hop systems are discussed. The characteristics of lightwave technology that facilitate the design of wavelength-division-multiplexing (WDM) networks are reviewed, and it is explained how WDM local networks can be built based on the single-hop and multihop approaches. Various categories of single-hop systems are discussed: experimental systems, systems based on no pretransmission coordination, and systems based on pretransmission coordination, which also require a separate control channel. A simple classification for single-hop systems is provided. >

WDM-based local lightwave networks. I. Single-hop systems

For pt.I see ibid., vol.6, no.3, p.12-27, 1992. A survey of wavelength-division-multiplexing (WDM)-based local lightwave networks is presented. The general characteristics of multihop systems are discussed, and various multihop approaches are reviewed. The construction of optimal structures based on minimizing the maximum link flow and optimizations based on minimization of the mean network packet delay are also reviewed. Regular topologies that have been studied as candidates for multihop lightwave networks, including the perfect shuffle, the de Bruijn graph, the toroid, and the hypercube, are discussed. Near-optimal node placement algorithms and shared-channel multihop systems are also discussed. >

WDM-based local lightwave networks. II. Multihop systems

A communications network has a plurality of nodes interconnected by an optical transmission medium. The transmission medium is capable of a carrying a plurality of wavelengths organized into bands. A filter at each node for drops a band associated therewith and passively forwards other bands through the transmission medium. A device is provided at each node for adding a band to the transmission medium. Communication can be established directly between a pair of nodes in the network sharing a common band without the active intervention of any intervening node. This allows the network to be protocol independent. Also, the low losses incurred by the passive filters permit relatively long path lengths without optical amplification.

WDM optical network with passive pass-through at each node

http://www.hit.bme.hu/~jakab/edu/litr/Core/WDM/WDM%20Technology_and_Applications_5-3.pdf

A Review of WDM Technology and Applications

Explores design principles for next generation optical wide-area networks, employing wavelength-division multiplexing (WDM), and targeted to nationwide coverage. This almost-all-optical network will exploit wavelength multiplexers and optical switches in routing nodes, so that arbitrary virtual topologies may be imbedded on a given physical network. The virtual topology, which is packet switched and which consists of a set of all-optical lightpaths, is set up to exploit the relative strengths of both optics and electronics viz. packets of information are carried by the virtual topology "as far as possible" in the optical domain, but packet forwarding from lightpath to lightpath is performed via electronic switching, whenever required. Algorithms are developed so that the WDM-based network architecture will (a) provide a high aggregate system capacity due to spatial reuse of wavelengths, and (b) support a large and scalable number of users, given a limited number of wavelengths. The authors illustrate their approaches by employing experimental traffic statistics collected from NSFNET. >

Some principles for designing a wide-area optical network

Optical network technology will soon allow wavelength-multiplexed optical channels to be carried to multiple terminals, giving rise to new broadband network architectures and protocols. Two stages of evolution are anticipated, with transmission-only structures appearing first and networks with optical switching appearing later. Some basic transmission considerations relating to system operation over wide optical bandwidths for both local and longer distance networks are reviewed, and the present status of experimental optical networks and the components they use are discussed. >

G.R. Hill

Papers

Wavelength domain optical network techniques