Impairment-aware dynamic lightpath provisioning in mixed-line-rate networks

In Mixed-Line-Rate (MLR) networks, different line rates on different wavelengths can coexist on the same fiber. MLR brings flexibility to handle diverse demands by allowing each lightpath to be established end-to-end with different line rates, if necessary. However, advanced modulation techniques, which are required for high line rates, are highly susceptible to physical-layer impairments (PLIs), especially to the cross-phase modulation (XPM) induced by intensity-modulated channels. In this study, we investigate the impairment-aware lightpath provisioning problem for MLR networks. We consider a transparent optical network where we aim to maximize the number of established connections, while avoiding disrupting the existing lightpaths. We propose two different approaches: the first approach, Fixed Wavelength-Interval Allocation, takes PLIs into account implicitly, as signals for different line rates with different modulation formats are placed on channels over separate wavelength intervals. The second approach, Weighted Routing and Wavelength Assignment, handles the problem with a novel weight assignment scheme. We employ an auxiliary graph to capture the effects of PLIs on each channel with a weight-assignment scheme. Simulation results show that our approaches have better performance, in terms of bandwidth blocking ratio, utilization, and resource consumption with respect to the existing approaches. (C) 2014 Elsevier B.V. All rights reserved.