A new method to plan more realistic optical transparent networks

Optically transparent routing of wavelength division multiplexed (WDM) channels, which is a major trend in optical networks, seeks to lower cost by avoiding electronic signal regeneration at intermediate sites and to make the network more flexible in terms of transported modulation formats and rates. Consequently, assessing the expected transmission quality of an optical channel prior to establishing a connection may be useful in maintaining high availability. Many proposals aim at upgrading the control plane with a fast and accurate “quality of transmission” (QoT) estimator. However, uncertainties about the physical features of the network yield a residual uncertainty with the estimation. Usually this global uncertainty is partially accounted for either during the routing process by adding a fixed margin to the quality factor of the connection estimated from the nominal parameters of the lightpath, or after the routing process by placing regenerators along the previously calculated path according to the uncertainties accumulated along this path. We propose a new approach that, in addition, accounts for the accumulation of uncertainties in the physical parameters along a path during the route selection process. Hence our path selection and our planning results combine the details of the network physical resources with their associated level of reliability. This approach allows more relevant network utilization by mitigating the degradation of the quality of service due to uncertainties of the parameters describing the physical layer. We illustrate this advantage with a case study of a U.S.-wide core network. é 2010 Alcatel-Lucent.