Marianna Angelou

Experimental Demonstration of an Impairment Aware Network Planning and Operation Tool for Transparent/Translucent Optical Networks

Core optical networks using reconfigurable optical switches and tunable lasers appear to be on the road towards widespread deployment and could evolve to all-optical mesh networks in the coming future. Considering the impact of physical layer impairments in the planning and operation of all-optical (and translucent) networks is the main focus of the Dynamic Impairment Constraint Optical Networking (DICONET) project. The impairment aware network planning and operation tool (NPOT) is the main outcome of DICONET project, which is explained in detail in this paper. The key building blocks of the NPOT, consisting of network description repositories, the physical layer performance evaluator, the impairment aware routing and wavelength assignment engines, the component placement modules, failure handling, and the integration of NPOT in the control plane are the main contributions of this study. Besides, the experimental result of DICONET proposal for centralized and distributed control plane integration schemes and the performance of the failure handling in terms of restoration time is presented in this study.

Quantifying spectrum, cost, and energy efficiency in fixed-grid and flex-grid networks [Invited]

Single and multi-carrier networks offering channel rates up to 400 Gb/s are evaluated under realistic reach parameters. It is found that efficient spectrum utilization and fine bit-rate granularity are essential to achieve cost and energy efficiency. Additionally, the break-even cost of flexible orthogonal frequency division multiplexing transponders is examined under different settings. The break-even cost of a flexible transponder corresponds to the cost value for which the total cost of the network is equal to that of the related single-line-rate network. The impact of the traffic load, the additional cost required for flex-grid optical cross connects, the cost of spectrum, as well as the cost of fixed-grid transponders is examined.

Towards ultra-dense wavelength-to-the-user: The approach of the COCONUT project

This paper presents the high-level COCONUT architecture of an optical access network based on coherent technology, supporting ultra-dense Wavelength Division Multiplexing (WDM). The COCONUT network should allow for seamless evolution from present PON architectures, but also support new emerging applications such as mobile back-haul and front-haul. Coherent techniques will hence allow serving a higher number of users, thanks to ultra-dense WDM, and reaching higher power budget, thanks to higher sensitivity. These features should allow for economy of scale and network consolidation. Although coherent solutions are well-developed for core networks, the prohibitive cost of their optical and electronic parts makes them unsuitable for the massive deployment of access networks. To this aim, COCONUT will address realization of coherent transmitter/receivers exploiting low-cost components and simple electronics, so that the cost of typical line terminals would be affordable to the end-users. The paper presents an overview of the target results and key issues that are addressed by the COCONUT partners.

Offline Impairment Aware RWA Algorithms for Cross-Layer Planning of Optical Networks

Transparent optical networks are the enabling infrastructure for converged multi-granular networks in the future Internet. The cross-layer planning of these networks considers physical impairments in the network layer design. This is complicated by the diversity of modulation formats, transmission rates, amplification and compensation equipments, or deployed fiber links. Thereby, the concept of quality of transmission (QoT) attempts to embrace the effects of the physical layer impairments, to introduce them in a multi-criterium optimization and planning process. This paper contributes in this field by the proposal and comparative evaluation of two novel offline impairment aware planning algorithms for transparent optical networks, which share a common QoT evaluation function. The first algorithm is based on an iterative global search driven by a set of binary integer linear programming formulations. Heuristic techniques are included to limit the binary programming complexity. The second algorithm performs different pre-orderings of the lightpath demand, followed by a sequential processing of the lightpath demands. The performance and the scalability of both approaches are investigated. Results reveal great scalability properties of the global search algorithm, and a performance similar to or better than the sequential schemes.

Experimental demonstration of centralized and distributed impairment-aware control plane schemes for dynamic transparent optical networks

We demonstrate and compare distributed and centralized impairment-aware control plane schemes for transparent optical networks with dynamic traffic. Experimental results show that distributed scheme yields one fifth of setup time required by previously reported alternatives.

Cognitive dynamic optical networks [invited]

The use of cognition is a promising element for the control of heterogeneous optical networks. Not only are cognitive networks able to sense current network conditions and act according to them, but they also take into account the knowledge acquired through past experiences; that is, they include learning with the aim of improving performance. In this paper, we review the fundamentals of cognitive networks and focus on their application to the optical networking area. In particular, a number of cognitive network architectures proposed so far, as well as their associated supporting technologies, are reviewed. Moreover, several applications, mainly developed in the framework of the EU FP7 Cognitive Heterogeneous Reconfigurable Optical Network (CHRON) project, are also described.

A Novel Offline Physical Layer Impairments Aware RWA Algorithm With Dedicated Path Protection Consideration

Physical layer impairments accumulate as light propagates through a lightpath in the transparent optical networks. Therefore, it is possible to provision a lightpath, while its quality of transmission (QoT) does not meet the required threshold. Considering the physical layer impairments in the network planning phase gives rise to a set of offline Impairments Aware Routing and Wavelength Assignment (IA-RWA) algorithms. There are very few offline IA-RWA algorithms that consider dedicated path protection demands. In this work we propose a novel offline IA-RWA algorithm, called Rahyab and perform a comparative performance evaluation study, which considers two enhanced algorithms from the literature. Simulation results indicates that demand pre-processing, diverse routing, and adaptive wavelength assignment are the main reasons of lower blocking rate of Rahyab algorithm compared to the selected algorithms.

Considering physical layer impairments in offline RWA

We consider the offline version of the routing and wavelength assignment problem in transparent all-optical networks. In such networks and in the absence of regenerators, the signal quality of a transmission degrades due to physical layer impairments. Certain physical effects cause choices for one lightpath to affect and be affected by the choices made for other lightpaths. This interference among lightpaths is particularly difficult to formulate in an offline algorithm, since in this version of the problem we start without any established connections, and the utilization of lightpaths are the variables of the problem. For this reason the majority of work performed in this field either neglects lightpath interactions or assumes a worst case interference scenario. In this article we present a way to formulate interlightpath interference as additional constraints on RWA and show how to incorporate these constraints in an IA-RWA algorithm that directly accounts for the most important physical layer impairments. The objective of the resulting cross-layer optimization problem is not only to serve the connection requests using the minimum number of wavelengths (network layer objective), but also to select lightpaths that have acceptable quality of transmission performance (physical layer objective).

Next generation flexible and cognitive heterogeneous optical networks

Optical networking is the cornerstone of the Future Internet as it provides the physical infrastructure of the core backbone networks. Recent developments have enabled much better quality of service/experience for the end users, enabled through the much higher capacities that can be supported. Furthermore, optical networking developments facilitate the reduction of complexity of operations at the IP layer and therefore reduce the latency of the connections and the expenditures to deploy and operate the networks. New research directions in optical networking promise to further advance the capabilities of the Future Internet. In this book chapter, we highlight the latest activities of the optical networking community and in particular what has been the focus of EU funded research. The concepts of flexible and cognitive optical networks are introduced and their key expected benefits are highlighted. The overall framework envisioned for the future cognitive flexible optical networks are introduced and recent developments are presented.

An offline impairment aware RWA algorithm with dedicated path protection consideration

We present excellent performance results for a novel offline physical layer impairment aware routing and wavelength assignment algorithm for various transparent all-optical networks, while considering dedicated path protection.