Abstract

Wavelength-division-multiplexing/frequency-division-multiplexing (WDM/FDM) technology will open up new opportunities for constructing a network that is bandwidth abundant and has a high degree of integrity. Such a network can be realized by using optical path-layer technology,¹ in which the transport network is divided into three layers: a circuit layer, a path layer, and a transmission-medium layer.² The optical path exploits not only the increase in point-to-point fiber transmission capacity with WDM but also the improved transport node (cross-connect) processing capability with wavelength routing.^3,4 Optical paths can take the form of wavelength paths (WPs) or virtual wavelength paths (VWPs).¹ In the WP scheme one wavelength is assigned to each path between path termination nodes [see Fig. 1(a)], whereas in the VWP scheme wavelengths are allocated link by link for each path [see Fig. 1(b)], which entails wavelength conversion at cross-connect nodes. The cross-connect system architectures needed for WPs and VWPs are described in Refs. 1 and 5.

© 1994 Optical Society of America