Adaptive Spectrum Control and Management in Elastic Optical Networks

Elastic optical networking has emerged in recent years as a promising solution for implementing flexible-bandwidth channels (flexpaths) that efficiently match the allocated bandwidth with traffic demands. By using agile granularities of spectral assignment, this kind of optical networks have significant advantages over conventional WDM networks, such as eliminating the bandwidth mismatch and reducing the guard bandwidth. However, the additional flexibility in such networks raises challenges in terms of effective control and management of spectrum resources for efficient spectral utilization. Among them, three important issues are (1) mitigation of spectral fragmentation, (2) implementation of impairment awareness and reliability against impairments, and (3) a fast and efficient restoration method to combat network failures.;This thesis focuses on an adaptive spectrum control and management scheme in elastic optical networks. Accounting for the above challenges, the scheme proposes three techniques correspondingly: (1) dynamic on-demand spectral defragmentation, (2) supervisory channel-based impairment awareness and adaptive combinational quality of transmission (QoT) restoration, and (3) supervisory channel-assisted active restoration. These three aspects serve as effective approaches to enhancing the network availability, reliability and survivability, respectively.;With spectral defragmentation, this thesis presents network node architecture designs and a scalable defragmentation algorithm. Simulation results show that the defragmentation technique is capable of reducing the service blocking probability by at least a factor of 2.;Secondly, with the adaptive combinational QoT restoration scheme (ACQR), this thesis proposes the use of modulation format switching and lightpath rerouting in a coordinative manner to combat dynamically-occurring impairments in fiber networks. Results show that ACQR can efficiently restore many simultaneously-degraded flexpaths and reduce the restoration blocking probability by a factor of 10, compared with the conventional rerouting method. In addition, it significantly saves the spectra used for QoT restoration.;At last, this thesis introduces the concept of supervisory channel-assisted active restoration to combat network failures. This method uses the channel condition information provided by the supervisory channel to support optimal path and modulation format selection, showing a potential to be much more efficient than traditional restoration schemes.