Raman Pumping as an Energy Efficient Solution for NyWDM Flexible-grid Elastic Optical Networks

This paper investigates transparent wavelength routed optical networks using three different fiber types NZDSF, SMF and PSCF - and validates the effectiveness of Hybrid Raman/EDFA Fiber Amplification (HFA) with different pumping levels, up to the moderate 60% pumping regime. Nodes operate on the basis of flexible-grid elastic NyWDM transponders able to adapt the modulation format to the quality-of-transmission of the available lightpath, exploiting up to five 12.5 GHz spectral slots. Results consider a 37- node Pan-European network for variable Raman pumping level, span length and average traffic per node. We show that HFA in moderate pumping regime reduces the power consumption and enhances spectral efficiency for all three fiber types with particular evidence in NZDSF. In essence to that, introduction of HFA is also beneficial to avoid blocking for higher traffic loads

Physical layer aware open optical networking

L'abstract è presente nell'allegato / the abstract is in the attachmen

Physical Layer Aware Optical Networks

This thesis describes novel contributions in the field of physical layer aware optical networks. IP traffic increase and revenue compression in the Telecom industry is putting a lot of pressure on the optical community to develop novel solutions that must both increase total capacity while being cost effective. This requirement is pushing operators towards network disaggregation, where optical network infrastructure is built by mix and match different physical layer technologies from different vendors. In such a novel context, every equipment and transmission technique at the physical layer impacts the overall network behavior. Hence, methods giving quantitative evaluations of individual merit of physical layer equipment at network level are a firm request during network design phases as well as during network lifetime. Therefore, physical layer awareness in network design and operation is fundamental to fairly assess the potentialities, and exploit the capabilities of different technologies. From this perspective, propagation impairments modeling is essential. In this work propagation impairments in transparent optical networks are summarized, with a special focus on nonlinear effects. The Gaussian Noise model is reviewed, then extended for wideband scenarios. To do so, the impact of polarization mode dispersion on nonlinear interference (NLI) generation is assessed for the first time through simulation, showing its negligible impact on NLI generation. Thanks to this result, the Gaussian Noise model is generalized to assess the impact of space and frequency amplitude variations along the fiber, mainly due to stimulated Raman scattering, on NLI generation. The proposed Generalized GN (GGN) model is experimentally validated on a setup with commercial linecards, compared with other modeling options, and an example of application is shown. Then, network-level power optimization strategies are discussed, and the Locally Optimization Global Optimization (LOGO) approach reviewed. After that, a novel framework of analysis for optical networks that leverages detailed propagation impairment modeling called the Statistical Network Assessment Process (SNAP) is presented. SNAP is motivated by the need of having a general framework to assess the impact of different physical layer technologies on network performance, without relying on rigid optimization approaches, that are not well-suited for technology comparison. Several examples of applications of SNAP are given, including comparisons of transceivers, amplifiers and node technologies. SNAP is also used to highlight topological bottlenecks in progressively loaded network scenarios and to derive possible solutions for them. The final work presented in this thesis is related to the implementation of a vendor agnostic quality of transmission estimator for multi-vendor optical networks developed in the context of the Physical Simulation Environment group of the Telecom Infra Project. The implementation of a module based on the GN model is briefly described, then results of a multi-vendor experimental validation performed in collaboration with Microsoft are shown

Optimization of hybrid fiber amplifiers in uncompensated links designed for NyWDM transmission

Uncompensated links are the state of art in nowadays optical communications. Its deployment is being carried-out instead of the typical compensated links (such as Chirped _bers). This project focus on the optimization of the link through the use of hybrid Raman-EDFA ampli_ers, HFA. Therefore, we propose optimization rules for HFA in NyWDM transmission over these uniform uncompensated links and for it, we introduce a _ber Raman merit parameter showing that noise reduction is always dominant on NLI enhancement. Before that, a basical explanation of optical communications performance is explained where we will treat the optical _ber, optical ampli_ers and the GN-Model.Grado en Ingeniería de Tecnologías de Telecomunicació

Cognitive and Autonomous Software-Defined Open Optical Networks

L'abstract è presente nell'allegato / the abstract is in the attachmen

HFA optimization for nyquist WDM transmission

We propose optimization rules for HFA in NyWDM transmission over uniform uncompensated links, and for moderate pumping regime we introduce a fiber Raman merit parameter showing that noise reduction is always dominant on NLI enhancement

HFA optimization for nyquist WDM transmission

We propose optimization rules for HFA in NyWDM transmission over uniform uncompensated links, and for moderate pumping regime we introduce a fiber Raman merit parameter showing that noise reduction is always dominant on NLI enhancement

Impact of physical layer parameters on the design of core optical networks

The advent of Coherent-detection systems supported by Digital-Signal-Processing (DSP) makes it possible to carry out electronic fiber chromatic dispersion and allows us to use multi-level modulation formats. These formats are affected by fiber non-linearity due to small spacing between constellations, especially in the high cardinality number modulation formats. Main disadvantage of Non-Linear Interference (NLI), which is considered as a limiting factor for performance, is to limit the OSNR, which in turn limits the maximum reach of the link. In the novel Uncompensated Transmission (UT) propagation regimes, it is possible to carry out system performance prediction based on relatively simple analytical non-linear propagation models. In this thesis, we use what is called the Gaussian-Noise (GN) model which shows high prediction ability in a single span and multi-span links. The main target of the exploitation of the physical link is optical network optimization. OSNR was previously considered to depend upon the noise produced by the amplifier, the only source of noise; NLI now is considered as additive Gaussian noise as stated in the GN- model and it depends on all the physical link parameters, but independent of the transceiver. This dependency on physical parameters and in-dependency on the transceiver leads us to think of the optimization of the link which will be the target of our work and see how this optimization could be reflected at the network level. The thesis work regards the implementation of the GN-model in optical network, both the standard wavelength division multiplexing (WDM) and the Elastic Optical Networks (EONs). We investigate connection provisioning algorithms on optical infrastructures for three different architectures: fixed grid WDM with fixed-rate multilevel modulation, fixed-grid WDM with time-domain hybrid modulation formats and flexible grid. We perform a sensitivity analysis of network and physical layer parameters, such as the link length, the traffic load, different fiber types and the Q margin, to understand how each parameter influences the network design. Besides comparing the two paradigms of flexible and fixed grid networks, including both pure and hybrid modulation formats, in terms of their spectral efficiency and power consumption, we show the importance of integrating a detailed physical layer modelling in the network design phase. Flexible-grid optical networks turned out to be the most convincing candidate for the evolution of backbone optical networks in order to face the envisioned growth of IP traffic. They combine the maximization of spectral efficiency with the flexibility of traffic load per lightpath allowing a full exploitation of transmission level potentialities joined to the flexibility in satisfying traffic demand. In this network scenario, we propose an original approach to the logical topology design (LTD) problem in the offline planning phase. We deal with the LTD problem using heuristic algorithms incorporating a detailed transmission layer model. Several heuristic algorithms, dealing with traffic demands in different ordering, are considered for lightpath provisioning. Traffic ordering schemes are set based on two parameters: traffic demands capacity and lightpath physical route length. Through simulative analyses, we provide a performance comparison of different heuristics, using parameters like spectral efficiency, amount of blocked traffic and total number of transceivers. Furthermore, a constant need to improve network capacity and reduce power consumption in current fixed- grid WDM networks motivates researchers to find alternative solutions other than replacing the deployed equipment. One of the possible solutions is the use of hybrid EDFA/Raman amplifier, which improves signal- to-noise- ratio in a point to point link. This work aims at quantifying, by means of a detailed power model, the effect of these novel ideas on the power consumption of the network, which is key to build a future green Internet. Results show that hybrid amplification in moderate pumping regime minimizes total network power consumption for networks made up of all three fiber types in particular for non- zero dispersion- shifted fiber. Moreover, we analyze transparent wavelength routed optical networks using three different typical fiber types: NZDSF, SMF and PSCF and verify the effectiveness of Hybrid Raman/EDFA Fiber Amplification (HFA) with incremental pumping levels, up to the moderate pumping regime. Traffic is conveyed and retrieved in nodes by the use of flexible-grid elastic Nyquist Wavelength Division Multiplexing (WDM) transponders able to adapt the modulation format and the occupied bandwidth - and the corresponding delivered rate - to the quality-of-transmission of the available lightpath, using up to five ITU-T prescribed 12.5 GHz spectral slots. Impact of a detailed physical layer is considered considering both the impact of accumulation of ASE noise introduced by amplifiers and of non-linear interference generated by non-linear fiber propagation. We show that HFAs in moderate pumping regime reduces the spectral occupancy for all three fiber types with evidence in NZDSF. In essence to that, introduction of HFA is also beneficial to avoid blocking for higher traffic loads. Network Simulations considered several networking scenarios, where different heuristics are used to solve Resource and Spectrum Allocation (RSA) problems.Simulations are performed on different randomly generated and real networks to support the argument titling Next-Generation optical networks