Path layer technologies will play a key role in the development of a powerful and failure resilient B-ISDN. So far, they have been based on electrical technologies. This paper highlights WDM/FDM techniques and demonstrates that optical paths can greatly enhance the path layer capability and, therefore, the network performance. It is also shown that effective network failure restoration can be achieved with optical paths. The applicability of the Wavelength Path (WP) technique to global area networks is revealed by comparing different optical path realization techniques. WP's are applied to the national backbone network example to evaluate the required number of wavelengths, and to identify optical cross-connect node requirements. We then propose a new optical path concept: the Virtual Wavelength Path (VWP). In the VWP scheme, wavelengths are assigned on a link-by-link basis. In other words, the wavelength assigned to a wavelength path has only local significance. Significant benefits of the VWP such as the simplified path accommodation design within a transmission facility network and the reduced number of wavelengths needed, are elucidated. An optical cross-connect node architecture that enables the VWP's is also proposed. The architecture allows the VWP concept to be realized with commercially available optical technologies. The optical path layer concept proposed in this paper exploits and consolidates the layered transport network architecture and optical technologies, and will open up new opportunities for creating a B-ISDN that is bandwidth abundant and has a high degree of integrity.
