Olivier Rival

On nonlinear distortions of highly dispersive optical coherent systems

We investigate via experiments and simulations the statistical properties and the accumulation of nonlinear transmission impairments in coherent systems without optical dispersion compensation. We experimentally show that signal distortion due to Kerr nonlinearity can be modeled as additive Gaussian noise, and we demonstrate that its variance has a supra-linear dependence on propagation distance for 100 Gb/s transmissions over both low dispersion and standard single mode fiber. We propose a simple empirical model to account for linear and nonlinear noise accumulation, and to predict system performance for a wide range of distances, signal powers and optical noise levels.

Datarate Adaptation for Night-Time Energy Savings in Core Networks

We examine how datarate-adaptive transceivers can be used to follow the pronounced variations in requested bandwidth in core networks and therefore allow significant energy savings compared to static networks configured to support the peak traffic all the times. We investigate two schemes for datarate adaptation in optical transceivers: modulation-format adaptation and symbol-rate adaptation, and show how they yield comparable energy savings but through very different mechanisms. We quantify these energy savings with respect to static networks for the case of a European backbone network and find potential for up to 30% of savings when the two schemes are combined.

Impact of Inter-Channel Nonlinearities on the Planning of 25–100 Gb/s Elastic Optical Networks

In this paper, we examine how typical transmission systems can be made tunable in datarate, up to 100 Gb/s, through modulation-format versatility. We investigate through extensive numerical simulations the available reach versus datarate, taking in particular into account the nonlinear interaction between channels in this mixed-format context. We show how these versatile transmission systems can be used to design a so-called elastic optical network in which the datarate of a wavelength is adapted to both the traffic that needs to be transported and the amount of physical impairments that need to be overcome. We examine the benefits of such elastic optical networks in the case of a European backbone network, showing that elastic architectures outperform fixed-rate networks by up to 21% in terms of required number of opto-electronic interfaces.

Advantages of elasticity versus fixed data-rate schemes for restorable optical networks

We investigate link restoration in optical networks carrying multiple data-rates. We compare rate-tunable opto-electronic interfaces (elastic) versus rate-specific (fixed) technologies and show the reconfiguration ability of elastic interfaces strongly reduces the required spare resources.

Elastic optical networks: The global evolution to software configurable optical networks

Worldwide operator deployment of high-speed 100G coherent optical networks is currently underway. To ensure a competitive solution offering significant performance improvements to cope with the ever-increasing traffic demand, a novel network concept has been proposed for improved resource utilization based on “elasticity”; specifically, the ability to make a number of previously fixed transmission parameters tunable, for example optical data rate or channel spacing. The benefits are numerous, including increased network capacity, lower cost per bit, and improved energy efficiency and scalability. In this paper, we review the work carried out within the Cooperation for a Sustained European Leadership in Telecommunications (CELTIC) Elastic-Optical NETwork (EO-Net) project towards advancing the state of software-configurable optical networking. We identify the key building blocks for enabling elastic optical networks to provide desired performance improvements over static optical networks. We examine the design of elastic transponders capable of data rate adaptation, interfaces between client packet devices and transponders supporting flexible traffic aggregation, and associated algorithms for traffic grooming and routing. We also perform network cost/energy analyses. Finally, we review the experimental demonstration of such elastic functionalities.

Impact of transparent network constraints on capacity gain of elastic channel spacing

We compare fixed-grid network architectures with variable-spacing OFDM based solutions. We show that capacity gains can reach up to 50% but are strongly affected by physical and topological constraints of transparent networks and traffic statistics.

Efficiency gain from elastic optical networks

We compare the cost-efficiency of optical networks based on mixed datarates (10, 40, 100Gb/s) and datarate-elastic technologies. A European backbone network is examined under various traffic assumptions (volume of transported data per demand and total number of demands) to better understand the impact of traffic characteristics on cost-efficiency. Network dimensioning is performed for static and restorable networks (resilient to one-link failure). In this paper we will investigate the trade-offs between price of interfaces, reach and reconfigurability, showing that elastic solutions can be more cost-efficient than mixed-rate solutions because of the better compatibility between different datarates, increased reach of channels and simplified wavelength allocation.

An energy-efficient node interface for optical core networks

This paper investigates the potential reduction of energy consumption in core optical network by introducing within core nodes an intermediate optical cross connect between optoelectronic devices and the router. By bringing both energy efficiency and flexibility at the same time, the solution is suitable for shaping the evolution of optical core networks over the mid and long term towards shifting patterns of dynamic optical network resources use. The benefits in power consumption of the proposed solution are investigated through simulations and compared to alternatives currently implemented within core nodes.

System design tool for high bit rate terrestrial transmission systems with coherent detection

Coherent detection offers the ability to compensate for linear transmission impairments such as fiber chromatic dispersion and polarization-mode dispersion in the digital domain, thereby enabling dispersion-uncompensated optical transmission for high performance and high cost effectiveness. In dispersion-uncompensated transmission systems, the statistics of optical nonlinearity induced distortions have been proven to be essentially Gaussian-distributed, and new physical models have emerged showing profound differences with respect to legacy systems based on direct detection. From such differences stems the need to adapt the design tool to capture these new propagation properties. In that respect, we propose a model for performance prediction, which is used to derive a simple yet effective feasibility parameter to be embedded in the design tool. The feasibility parameter is experimentally validated with real time product transponders, and realistic system configurations: a precision of ±0.5 dB is achieved for 40 Gb/s, 100 Gb/s and 400 Gb/s coherent channels, which represents an improvement of more than 3 dB over the design tool using the nonlinear phase shift as the criterion.

Upgrading optical networks with elastic transponders

We show how rate-adaptive transponders help reduce the cost of optical networks compared to single and mixed-line-rate solutions through a better ability to accommodate growth of traffic and uncertainties in traffic matrices during network upgrades.