The tremendous growth in the volume of telecommunication traffic has undoubtedly triggered an unprecedented information revolution. The emergence of high-speed and bandwidth-hungry applications and services such as high-definition television (HDTV), the internet and online interactive media has forced the telecommunication industry to come up with ingenious and innovative ideas to match the challenges. With the coming of age of purposeful advances in Wavelength Division Multiplexing (WDM) technology, it is inherently practicany possible to deploy ultra-high speed all-optical networks to meet the ever-increasing demand for modern telecommunication services. All-optical networks are capable of transmitting data signals entirely in the optical domain from source to destination, and thus eliminate the incorporation of the often bulky and high-energy consuming optical to-electrical-to-optical (OEO) converters at intermediate nodes. Predictably, all-optical networks consume appreciably low energy as compared to their opaque and translucent counterparts. This low energy consumption results in lower carbon footprint of these networks, and thus a significant reduction in the greenhouse gases (GHGs) emission. In addition, transparent optical networks bring along other additional and favourable rewards such as high bit-rates and overall protocol transparency. Bearing in mind the aforementioned benefits of transparent optical networks, it is vital to point out that there are significant setbacks that accompany these otherwise glamourous rewards. Since OEO conversions are eliminated at intermediate nodes in all-optical networks, the quality of the transmitted signal from source to destination may be severely degraded mainly due to the cumulative effect of physical-layer impairments induced by the passage through the optical fibres and associated network components. It is therefore essential to come up with routing schemes that effectively take into consideration the signal degrading effects of physical -layer impairments so as to safeguard the integrity and health of transmitted signals, and eventually lower blocking probabilities. Furthermore, innovative approaches need to be put in place so as to strike a delicate balance between reduced energy consumption in transparent networks and the quality of transmitted signals. In addition, the incorporation of renewable energy sources in the powering of network devices appears to gain prominence in the design and operation of the next-generation optical networks. The work presented in this dissertation broadly focuses on physical-layer impairment aware routing and wavelength assignment algorithms (PLIA-RWA) that attempt to: (i) achieve a sufficiently high quality of transmission by lowering the blocking probability, and (ii) reduce the energy consumption in the optical networks. Our key contributions of this study may be summarized as follows: Design and development of a Q-factor estimation tool. Formulation, evaluation and validation of a QoT-based analytical model that computes blocking probabilities. Proposal and development of IA-RWA algorithms and comparison with established ones. Design and development of energy-efficient RWA schemes for dynamic optical networks.
Physical Layer Impairments in the Optimization of the Next-Generation of All-Optical Networks
