nications services in almost every region of the world. In this issue, we have ... tectures, dynamic impairment-aware optical networks, lightpath bundling and ...
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SERIES EDITORIAL
OPTICAL ACCESS AND TRANSPORT NETWORKS
Osman S. Gebizlioglu
S
Vijay Jain
ince OFC/NFOEC ’12, the premier global communications industry event of the year, we have been seeing a steady stream of news regarding field trials and implementations of 100 Gb/s optical transport systems in carrier networks. As announced in our May 2012 OCS editorial, global popularity of this topic led us to designate high-speed optical transport as the feature topic for the November 2012 OCS issue. We look forward to showcasing the dynamic response of the global industry to the growing demand by subscribers for broadband telecommunications services in almost every region of the world. In this issue, we have selected six contributions that address high-capacity orthogonal frequency-division multiple access (OFDMA)-based optical access network architectures, dynamic impairment-aware optical networks, lightpath bundling and anycast switching in multilayer networks, interference cancellation in optical code-division multiple access (CDMA) systems, telephone systems powered over optical fiber, and protection in time-division multiplexing (TDM) passive optical networks (PONs). Thus, we have brought together advances in both optical access and transport networks in this OCS issue. In the first contribution, “An OFDMA-Based Optical Access Network Architecture Exhibiting Ultra-High Capacity and Wireline-Wireless Convergence,” K. Kanonakis, I. Tomkos, H. G. Krimmel, F. Schaich, C. Lange, E. Weis, J. Leuthold, M. Winter, S. Romero, P. Kourtessis, M. Milosavljevic, I. Cano, and J. Prat present a novel optical access network architecture based on OFDMA technology and applied on a PON topology. In compliance with next generation optical access (NGOA) requirements, this architecture is aimed at outperforming existing PON solutions in terms of total capacity, bandwidth allocation flexibility, number of users, and network reach. Furthermore, it provides the opportunity for convergence with wireless technologies and a smooth migration path from legacy access solutions like TDMA-PONs and digital subscriber line (DSL). In the second contribution, “Benefits of Implementing a Dynamic Impairment Aware Optical Network: Results of
IEEE Communications Magazine • August 2012
John Spencer
EU Project DICONET,” M. Angelou, S. Azodolmolky, I. Tomkos, J. Perelló, S.Spadaro, D. Careglio, K.Manousakis, P. Kokkinos, E. Varvarigos, D. Staessens, D. Colle, C. V. Saradhi, M. Gagnaire, and Y. Ye describe a comprehensive solution that utilizes dynamic optical networking along with the valuable physical-layer information of a reconfigurable WDM core network to provide a smooth transition from the quasi-static networking of today to an intelligent reconfigurable and physical-impairment-aware architecture. They discuss the benefits of implementing the DICONET solution, and present some of the major achievements of the project that support both the planning and operation phases of a core optical network. In the third contribution, “Lightpath Bundling and Anycast Switching (LB+AS): A New Paradigm for Multilayer Optical Networks,” P. Pavon-Marino and J-L IzquierdoZaragoza present a case study to show significant performance and cost benefits that LB+AS can bring to the network and its inherent scalability. In IP over wavelengthdivision multiplexing (WDM) multilayer optical networks, IP routers are interconnected by all-optical channels called lightpaths, of typical rates of 10, 40, or, more recently, 100 Gb/s. In this context, lightpath bundling (LB) and anycast switching (AS) are control plane and data plane techniques, respectively, and both of them are implemented in the IP routers. LB permits grouping a set of lightpaths between two nodes that follow a common route so that they are perceived by the IP layer as a single virtual link of aggregated capacity. In its turn, AS functions to instruct the router to implement a per-packet granularity balancing of the traffic among the lightpaths in the bundle, reducing the packet delay and the buffering requirements in the node. This should proceed transparently, and, to the IP layer that, because of the LB configuration, sees the bundled lightpaths as a single entity. In this article, the combined application of the LB and AS techniques is proposed as a new paradigm (LB+AS) for optical networks. Applying the LB+AS concept requires seamless changes in the electronic equipment and no changes in the optical infrastructure.
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SERIES EDITORIAL In the fourth contribution, “Interference Cancellation in Optical CDMA Systems via Advanced Binary Optical Logic Gate Elements,” S. A. Nezamalhosseini, F. Marvasti, B. M. Ghaffari, and J. A. Salehi present an all passive optical iterative interference cancellation method for optical CDMA. They propose a receiver structure based on advanced binary optical logic gates (ABOLGs). Since the performance bottleneck in optical communication systems is the conversion from optical to electronic domains for optical detectors, the interference cancellation is performed in the optical domain. In incoherent optical communication systems, only positive values for the optical signals are used, while negative values are bypassed using logic arrays. In the simulations, the authors consider multiple access interference and neglect other sources of noise. Simulation results show that in future optical communications systems, the interference can be eliminated completely using iterative methods in the optical domain. In the fifth contribution, “Optically Powered Telephone System over Optical Fibre,” S. Al-Chalabi discusses the cost, availability, and regulatory requirements for plain old telephone service (POTS) and argues that competitive optical communications systems must achieve the same levels in cost, availability, and regulatory compliance. He presents an optical communications system that meets these requirements, in which the laser in the customer premises equipment (CPE) is replaced by a reflecting interferometer for the outgoing call channel, and part of the received optical power is converted to electrical power using photovoltaic cells and an energy storage device to drive the CPE.
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In the sixth contribution, “Cost-Efficient Protection in TDM PONs,” C. Mas Machuca, J. Chen, and L. Wosinska propose a cost-efficient way to provide protection in TDM PONs considering different deployment scenarios with respect to population density in the access network service area. The cost efficiency is obtained by taking advantage of investment cost reduction realized by sharing the same duct with both working and protection fibers. In order to evaluate the investment associated with the deployment of the proposed protection schemes, they take into account three different approaches: • Provide protection in the access network from the beginning. • Invest initially in an unprotected architecture, keeping in mind a future upgrade with protection resources. • Roll out an unprotected access network, and, if needed in the future, invest in deployment of protection resources. The cost parameters considered include investment in the infrastructure and installation, as well as the operational expenditures associated with the failure mitigation and service interruption penalties. They show that the proposed reliable PON architectures can achieve the significant reduction of service interruption with a minimal increase of the investment cost, leading to a significant decrease in the total cost of ownership. Finally, some useful guidance on cost-efficient deployment of protection in fiber access networks is provided along with a sensitivity study to examine the key cost factors. We thank the authors and reviewers for their contributions.
IEEE Communications Magazine • August 2012
