On the Impact of Lightpath Rerouting on Connection Provisioning with Transmission Impairments in WDM All-Optical Networks

In transparent optical networks, signals can propagate over long distances without electrical regeneration, causing physical layer impairments to accumulate and make lightpaths’ Quality of Transmission (QoT) become potentially unacceptable. Depending on the channel load and transmission distance some paths cannot be set up fully transparently because the transmission quality requirements (i.e. pre-FEC Bit Error Rate (BER) = 10 -9 or Q-factor = 15.56 dB) cannot be fulfilled. This result might have a severe consequence on the performance of all-optical networks especially in terms of rejection ratios. In this paper, we propose a new lightpath rerouting algorithm to optimize network resources allocation in WDM all-optical networks in order to set up an incoming lightpath demand to be blocked for lack of resources or due to the absence of a suitable path and a suitable wavelength that meet the minimum QoT requirements. Rerouting aims at reassigning the wavelength and/or the path of one or several established connections in order to free enough wavelengths to satisfy the incoming demand. Rerouting refers implicitly to dynamic traffic. Simulation results show that our algorithm improves the rejection ratio and is less CPU time consuming than rerouting algorithms previously presented in the literature.