Submarine systems have recently evolved from turnkey systems into an open cable approach, where new metrics describing wet plant performance have been defined. The transmission GSNR has been standardized and is measured together with the OSNR in cable commissioning to characterize open submarine links. We propose in this paper a method based on numerical simulation to accurately predict the achievable capacity of open cables using only the commissioning parameters. We also assess the impact of the measurement uncertainties during commissioning on capacity prediction. Finally, we apply the proposed method to realistic subsea links and show how the uncertainty on the capacity estimate can be reduced further when using the commissioning measurements to reduce the uncertainty on line parameters.

A 26dBm L-Band Lumped Raman Fibre Amplifier based on highly non-linear Ge-doped Photonic Crystal Fiber is reported. The amplifier uses commercially available pump laser diodes, and has a very fast transient suppression time of 10μs.

We propose a set of physical parameters for GMPLS signaling to establish bi-directional paths. This reduces the amount of flooded information and speeds-up the path establishment while keeping its risk of unfeasibility lower than 2%.

Optically transparent routing of wavelength division multiplexed (WDM) channels, which is a major trend in optical networks, seeks to lower cost by avoiding electronic signal regeneration at intermediate sites and to make the network more flexible in terms of transported modulation formats and rates. Consequently, assessing the expected transmission quality of an optical channel prior to establishing a connection may be useful in maintaining high availability. Many proposals aim at upgrading the control plane with a fast and accurate “quality of transmission” (QoT) estimator. However, uncertainties about the physical features of the network yield a residual uncertainty with the estimation. Usually this global uncertainty is partially accounted for either during the routing process by adding a fixed margin to the quality factor of the connection estimated from the nominal parameters of the lightpath, or after the routing process by placing regenerators along the previously calculated path according to the uncertainties accumulated along this path. We propose a new approach that, in addition, accounts for the accumulation of uncertainties in the physical parameters along a path during the route selection process. Hence our path selection and our planning results combine the details of the network physical resources with their associated level of reliability. This approach allows more relevant network utilization by mitigating the degradation of the quality of service due to uncertainties of the parameters describing the physical layer. We illustrate this advantage with a case study of a U.S.-wide core network. © 2010 Alcatel-Lucent.

The capacity growth driven by increasing traffic and the introduction of new devices and technologies has resulted in new functionalities in optical networks. The property of transparency enables compatibility between different system generations and the coexistence of multiple bit-rates without raising the global network cost. In a transparent network, the signals travel through many links and nodes without the need for opto-electronic regeneration, accumulating physical impairments. Therefore, standard point-to-point test-bed set-ups are no longer adequate to emulate signals propagating in transparent optical networks. New test-beds integrating the different heterogeneity cases due to the use of transparent cross-connects becomes necessary. In this paper, we present various test-bed realizations accounting for the following network heterogeneities: fiber link heterogeneity and neighbor changes while a signal propagates in the fiber. To be able to emulate such network heterogeneity, we present a double-loop set-up. Such a set-up is then used to assess the propagation results obtained by simulation and validate the quality of transmission (QoT) estimators.

We experimentally investigate the quality of transmission in mesh networks relying on various fiber types. We show that the quality of transmission can be evaluated accurately using the weighted nonlinear phase criterion.

This paper discusses the impact of physical impairments estimation in designing and operating reconfigurable optical transparent networks, accounting for uncertainties and the confidence level of the connection feasibility predictions.

Confidence level on connection feasibilities is used to obtain Q-estimate margins when parameter uncertainties are considered. Adding such margins to the Q-estimate instead of fixed margins gives 22% fewer regenerators at same 97.5% confidence level.

Optical network telecommunication operators are adopting optical transparency to make the channel routing more flexible, optimize their cost and meet customer requirements. But, the optical signal accumulates physical impairments along the transmission so that its quality should be assessed before setting-up the connection. The relevance of an estimate depends on the uncertain knowledge of the physical parameters. This paper shows the importance of accounting for uncertainties within a physical impairment aware dimensioning tool.

We justify a lightpath characteristic dependent margin when estimating the quality of transmission for the establishment of a connection by showing the resulting better prediction accuracy and eventually the reduction of the required transmission resources.

To cope with increasing traffic, optical networks have steadily adopted faster interfaces. Interfaces working at 40 Gb/s were recently introduced in networks already deployed at 10 Gb/s; moreover, 100 Gb/s interfaces have been demonstrated in laboratory experiments [1]. As this upgrade in bit-rate tends to evolve over time scales faster than the lifetime of deployed systems, wavelength division multiplexed (WDM) systems may be required to support simultaneous transmission of signals modulated at different rates. These signals can have very different transmission properties and optimal designs often employ unique modulation formats for each bit rate. For example, non return to zero on-off keyed modulation is commonly used at 10 Gb/s, whereas phase-shift-keyed modulation formats, such as differential phase shift keying, are used at 40 Gb/s. More complex modulation formats are proposed at 100 Gb/s and recent studies consider the use of orthogonal frequency division multiplexing to make the channel capacity flexible, ranging from 10 up to 100 Gb/s and higher [2]. This wide variation in modulation technologies motivates the use of a network infrastructure that supports transmission heterogeneity without costly changes when a new bit rate or format is introduced. Transparent networks have the advantage of providing a flexible infrastructure with the potential to enable the introduction of new modulation technologies by changing only the extremity interfaces. Optical transparency is possible thanks to the introduction of optical switches, such as wavelength selective switches (WSS), avoiding systematic optoelectronic conversion at nodes, and also thanks to improvements in transmission performance, enabling reaches of several thousand kilometers and many nodes before needing optoelectronic regeneration.

As optical networks are moving towards transparency to save expensive optoelectronic conversions, 40 Gb/s transmission technology appears on the field to meet the increasing capacity requirements. An advantage of transparent network is its independence of the bit rate and modulation format. Hence the transition from 10 to 40 Gb/s in a transparent network can be imagined as a gradual replacement of transponders working at 10 Gb/s with transponders at 40 Gb/s and the co-existence of both bit rates. In this paper we propose a routing method optimizing the exploitation of unused capacity in 40 Gb/s channels and also reducing the number of optoelectronic devices; we name this criterion ‘10/40 Gb/s synergy’. We show that routing 10 Gb/s demands at different bit rates is more performing than a routing at a fixed bit rate; we also show that the synergy minimize the number of required 40 Gb/s transponder as a function of traffic characteristics.

We demonstrate long haul transmission in a circulating loop with impairment-constrained wavelength-assignment to channels simultaneously propagating over different circulation distances.

The emergence of new devices and technologics introduces new trends and design issues for optical transport networks. The higher performance of transmission and switch systems enables the reduction of optoelectronic conversions in intermediate nodes with the introduction of transparency in the network. Simultaneously, the system of Automatic Switched Optical Networks (ASON) describes the rules for the construction of a network enabling cost reduction, above all for maintenance, and fast and automatic reconfiguration. Two axes have to evolve to make possible all these proprieties: the control plane and its relative set of protocols, to manage the network working for the network automation, and also the systems and tools enabling transparency and reconfigurability. In this article we focus oil the second axis applied to an automatic transparent network. To cite this article: A. Morea et al., C. R. Physique 9 (2008). (C) 2008 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.

We investigate a new routing algorithm able to finely consider signal quality during propagation in an optical WDM meshed network. To evaluate the quality of transmission, we propose an analytical estimator based on experimental measurements, along with an assessment of its accuracy. The proposed algorithm "places" optoelectronic (OEO) regenerators, taking into account the wavelength occupation and the quality of transmission of the selected optical path, so it can optimize the number of required OEO operations for a connection. To validate the interest of the proposed algorithm and the quality of transmission estimator, we present dimensioning results for two different routing strategies and two different estimators of transmission quality. The performance of the proposed methods is particularly relevant compared to works in present literature where system characteristics are not ideal. (C) 2007 Optical Society of America.

Reconfigurable transparent networks are now a reality in the core layer thanks to the implementation of innovative transmission and wavelength routing sub-systems. Transparency on a large scale opens up new perspectives in terms of scalability and flexibility. There are numerous promising technologies to achieve that goal but it is likely that only few of them will really prevail in the field. For instance, the compliance with the already installed transmission infrastructures or the power consumption consideration may prevent a technology from appearing in a real optical network. This paper presents some of our current research directions that exhibit a high potential to meet the market requirements for the future dynamic transparent core networks.