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  • 1. Abeywickrama, S.
    et al.
    Furdek, Marija
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab). University of Zagreb, Faculty of Electrical Engineering and Computing, Dept. of Telecommunications, Croatia.
    Monti, Paolo
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Nag, A.
    Wong, E.
    Dual-homing based protection for enhanced network availability and resource efficiency2014In: Asia Communications and Photonics Conference, ACP, 2014Conference paper (Refereed)
    Abstract [en]

    An approach to enhance core network survivability by utilizing dual-homing capabilities of the access network. Results reveal significant improvements in core network resource utilization and connection availability, suggesting benefits to network operators and service providers.

  • 2. Abeywickrama, S.
    et al.
    Wong, E.
    Furdek, Marija
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Monti, Paolo
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Energy-efficient survivability for core networks using dual-homing2015In: Asia Communications and Photonics Conference, ACPC 2015, 2015Conference paper (Refereed)
    Abstract [en]

    This paper studies the energy efficiency of exploiting dual-homing in access network to provide core network survivability. Simulation results show reduced number of utilized wavelengths, suggesting significant energy saving opportunities in the core network. © 2015 OSA.

  • 3. Abeywickrama, Sandu
    et al.
    Furdek, Marija
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Monti, Paolo
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Wong, Elaine
    Protecting core networks with dual-homing: A study on enhanced network availability, resource efficiency, and energy-savings2016In: Optics Communications, ISSN 0030-4018, E-ISSN 1873-0310, Vol. 381, 327-335 p.Article in journal (Refereed)
    Abstract [en]

    Core network survivability affects the reliability performance of telecommunication networks and remains one of the most important network design considerations. This paper critically examines the benefits arising from utilizing dual-homing in the optical access networks to provide resource-efficient protection against link and node failures in the optical core segment. Four novel, heuristic-based RWA algorithms that provide dedicated path protection in networks with dual-homing are proposed and studied. These algorithms protect against different failure scenarios (i.e. single link or node failures) and are implemented with different optimization objectives (i.e., minimization of wavelength usage and path length). Results obtained through simulations and comparison with baseline architectures indicate that exploiting dual-homed architecture in the access segment can bring significant improvements in terms of core network resource usage, connection availability, and power consumption.

  • 4. Abeywickrama, Sandu
    et al.
    Furdek, Marija
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Monti, Paolo
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Wong, Elaine
    Protecting core networks with dual-homing: A study on enhanced network availability, resource efficiency, and energy-savings2016In: Optics Communications, ISSN 0030-4018, E-ISSN 1873-0310, Vol. 381, 327-335 p.Article in journal (Refereed)
    Abstract [en]

    Core network survivability affects the reliability performance of telecommunication networks and remains one of the most important network design considerations. This paper critically examines the benefits arising from utilizing dual-homing in the optical access networks to provide resource-efficient protection against link and node failures in the optical core segment. Four novel, heuristic-based RWA algorithms that provide dedicated path protection in networks with dual-homing are proposed and studied. These algorithms protect against different failure scenarios (i.e. single link or node failures) and are implemented with different optimization objectives (i.e., minimization of wavelength usage and path length). Results obtained through simulations and comparison with baseline architectures indicate that exploiting dual-homed architecture in the access segment can bring significant improvements in terms of core network resource usage, connection availability, and power consumption.

  • 5.
    Abtahi, Farzad
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Cavdar, Cicek
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Khanmohamadi, Sahar
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Mantelet, G.
    Archambault, E.
    Tremblay, C.
    Bélanger, M. P.
    Optimal Design of Cost- and Energy-Efficient Scalable Passive Optical Backbone Networks2012In: 2012 Asia Communications And Photonics Conference (ACP), 2012, AS3D.4- p.Conference paper (Refereed)
    Abstract [en]

    We propose an optimization model minimizing number of wavelengths in passive optical backbone networks and obtaining the same resource usage as in networks based on active switching while reducing both cost and power consumption.

  • 6.
    Ahmed, J
    et al.
    KTH.
    Monti, Paolo
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Spadaro, S
    Enhancing restoration performance using service relocation in PCE-based resilient optical clouds2014In: Conference on Optical Fiber Communication, Technical Digest Series, 2014Conference paper (Refereed)
    Abstract [en]

    This paper investigates the benefits of dynamic restoration with service relocation in resilient optical clouds. Results from the proposed optimization model show that service availability can be significantly improved by allowing a few service relocations.

  • 7.
    Ahmed, Jawwad
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Dynamic Resource Provisioning and Survivability Strategies in Optical Networks2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Optical networks based on Wavelength Division Multiplexing (WDM) technology show many clear benefits in terms of high capacity, flexibility and low power consumption. All these benefits make WDM networks the preferred choice for today’s and future transports solutions which are strongly driven by a plethora of emerging online services.

    In such a scenario, capability to provide high capacity during the service provisioning phase is of course very important, but it is not the only requirement that plays a central role. Traffic dynamicity is another essential aspect to consider because in many scenarios, e.g., in the case of real time multimedia services, the connections are expected to be provisioned and torn down quickly and relatively frequently. High traffic dynamicity may put a strain on the network control and management operations (i.e., the overhead due to control message exchange can grow rapidly) that coordinate any provisioning mechanisms. Furthermore, survivability, in the presence of new failure scenarios that goes beyond the single failure assumption, is still of the utmost importance to minimize the network disruptions and data losses. In other words, protection against any possible future failure scenario where multiple faults may struck simultaneously, asks for highly reliable provisioning solutions.

    The above consideration have a general validity i.e., can be equally applied to any network segment and not just limited to the core part. So, we also address the problem of service provisioning in the access paradigm. Long reach Passive Optical Networks (PONs) are gaining popularity due to their cost, reach, and bandwidth advantages in the access region. In PON, the design of an efficient bandwidth sharing mechanism between multiple subscribers in the upstream direction is crucial. In addition, Long Reach PONs (LR-PONs) introduces additional challenges in terms of packet delay and network throughput, due to their extended reach. It becomes apparent that effective solutions to the connection provisioning problem in both the core and access optical networks with respect to the considerations made above can ensure a truly optimal end-to-end connectivity while making an efficient usage of resources.

    The first part of this thesis focuses on a control and management framework specifically designed for concurrent resource optimization in WDM-based optical networks in a highly dynamic traffic scenario. The framework and the proposed provisioning strategies are specifically designed with the objective of: (i) allowing for a reduction of the blocking probability and the control overhead in a Path Computation Element (PCE)-based network architecture, (ii)  optimizing resource utilization for a traffic scenario that require services with diverse survivability requirements which are achieved by means of  dedicated and shared path-protection, and (iii) designing provisioning mechanism that guarantees high connection availability levels in Double Link Failures (DLF) scenarios. The presented results show that the proposed dynamic provisioning approach can significantly improve the network blocking performance while making an efficient use of primary/backup resources whenever protection is required by the provisioned services. Furthermore, the proposed DLF schemes show good performance in terms of minimizing disruption periods, and allowing for enhanced network robustness when specific services require high connection availability levels.

    In the second part of this thesis, we propose efficient resource provisioning strategies for LR-PON. The objective is to optimize the bandwidth allocation in LR-PONs, in particular to: (i) identify the performance limitations associated with traditional (short reach) TDM-PON based Dynamic Bandwidth Allocation (DBA) algorithms when employed in long reach scenarios, and (ii) devise efficient DBA algorithms that can mitigate the performance limitations imposed by an extended reach. Our proposed schemes show noticeable performance gains when compared with conventional DBA algorithms for short-reach PON as well as specifically devised approaches for long reach.

  • 8.
    Ahmed, Jawwad
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Cavdar, Cicek
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Monti, Paolo
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    A Dynamic Bulk Provisioning Framework for Concurrent Optimization in PCE-Based WDM Networks2012In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 30, no 14, 2229-2239 p.Article in journal (Refereed)
    Abstract [en]

    A centralized network control and management plane, such as the one based on a path computation element (PCE), is highly beneficial in terms of resource optimization in wavelength division multiplexing optical networks. Benefits of centralized provisioning are even more evident when connection requests are provisioned in batches, i.e., they allow a better use of network resources via concurrent optimization. In this study, a dynamic bulk provisioning framework is presented with the objective of optimizing the use of network resources that also presents, as an additional benefit, the ability to yield a reduction of the control plane overhead. The rationale behind the proposed framework is based on a mechanism in which the PCE client is allowed to bundle and simultaneously send multiple labeled switch path (LSP) requests to the PCE where, in turn, several bundles can be concurrently processed together as a single bulk. From the network deployment perspective, a PCE-based network architecture is proposed to practically realize this approach. For dynamic bulk provisioning of optical LSP requests, a time-efficient integer linear programming (ILP) model (LSP BP ILP) is presented to minimize the request blocking, the network resource consumption, and the network congestion. In addition, a heuristic based on a greedy randomized adaptive search procedure (GRASP), namely LSP_BP_GRASP, is also proposed as a scalable alternative. The presented results demonstrate significant advantages of the proposed PCE bulk provisioning framework based on concurrent optimization in terms of reduced blocking probability and control overhead when compared with conventional dynamic connection provisioning approaches processing a single connection request at a time.

  • 9.
    Ahmed, Jawwad
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Cavdar, Cicek
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Monti, Paolo
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Hybrid Survivability Schemes Achieving High Connection Availability With a Reduced Amount of Backup Resources2013In: Journal of Optical Communications and Networking, ISSN 1943-0620, E-ISSN 1943-0639, Vol. 5, no 10, A152-A161 p.Article in journal (Refereed)
    Abstract [en]

    Maximizing connection availability in WDM networks is critical because even small disruptions can cause huge data losses. However, there is a trade-off between the level of network survivability and the cost related to the backup resources to be provided. The 100% survivability can be achieved by dedicated path protection with multiple pre-reserved protection paths for each provisioned connection, i.e., DPP (1:N). Unfortunately, the blocking probability performance of DPP (1:N) is negatively affected by the large number of pre-reserved backup wavelengths standing-by unutilized. On the other hand, path restoration (PR)-based solutions ensure good blocking performance at the expense of lower connection availability.

    The work in this paper aims at finding hybrid network survivability strategies that combine the benefits of both techniques (i.e., high availability with low blocking rate). More specifically, the paper focuses on a double link failure scenario and proposes two strategies. The first one, couples dedicated path protection DPP (1:1) with path restoration (referred to as DPP + PR) to minimize the number of dropped connections. The second scheme adds up the concept of backup reprovisioning (BR), referred to as DPP + BR + PR, in order to further increase the connection availability achieved by DPP + PR. Integer Linear Programming (ILP) models for the implementation of the proposed schemes are formulated. Extensive performance evaluation conducted in a PCE-based WDM network scenario shows that DPP + BR + PR and DPP + PR can significantly lower the blocking probability value compared to DPP (1:2) without compromising too much in terms of connection availability.

  • 10.
    Ahmed, Jawwad
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Cavdar, Cicek
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Monti, Paolo
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Survivability strategies for PCE-based WDM networks offering high reliability performance2013In: 2013 Optical Fiber Communication Conference and Exposition and the National Fiber Optic Engineers Conference, OFC/NFOEC 2013, Optical Society of America, 2013, 6532695- p.Conference paper (Refereed)
    Abstract [en]

    Two approaches based on backup reprovisioning and path restoration are proposed for dynamic failure recovery in survivable, PCE-based, WDM networks. Results show that proposed schemes can achieve high connection availability in double link failure scenarios.

  • 11.
    Ahmed, Jawwad
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Chen, Biao
    Department of Optical Engineering, Zhejiang University.
    Mukherjee, Biswanath
    Efficient Inter-Thread Scheduling Scheme for Long-Reach Passive Optical Networks2013In: IEEE Communications Magazine, ISSN 0163-6804, E-ISSN 1558-1896, Vol. 51, no 2, S35-S43 p.Article in journal (Refereed)
    Abstract [en]

    These days there is a clear trend toward extending the reach of passive optical networks to cover large geographical areas, which enables reduction of the number of central offices and hence has the potential of cost saving in network operation. On the other hand, this reach extension necessitates the design of efficient dynamic bandwidth allocation schemes in order to tackle performance degradation caused by the increased propagation delay in long reach PONs. Among many existing approaches, the multi-thread-based DBA scheme where several bandwidth allocation processes are performed in parallel is considered one of the most effective options to improve network performance in LRPONs. We have found that without proper intercommunication between the overlapped threads, multi-thread DBA may lose efficiency and even perform worse than the conventional single-thread algorithm. With this in mind, this article reviews different inter-thread scheduling schemes for LR-PONs, and proposes a novel approach of integrating the key ideas of the existing ones. Extensive simulation results confirm that our proposed scheme can significantly improve DBA performance for LR-PONs under a variety of scenarios with consideration of different values of network load and reach.

  • 12. Al-Awis, S. N.
    et al.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Fotonik och mikrovågsteknik, FMI.
    Pang, Xiaodan
    RISE ACREO AB.
    Ozolins, O.
    Jacobsen, Gunnar
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Fotonik och mikrovågsteknik, FMI.
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Fattah, A. Y.
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Phenomenological formula for modelling of physical layer impairments in elastic optical networks2015In: Asia Communications and Photonics Conference, ACPC 2015, 2015Conference paper (Refereed)
    Abstract [en]

    An empirical modelling technique is introduced to estimate impact of physical layer impairments in elastic optical networks, which can be used to evaluate transmission quality. The model has been verified experimentally with accuracy beyond (97.3%). © 2015 OSA.

  • 13. Archambault, Emile
    et al.
    Alloune, Nabih
    Furdek, Marija
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Xu, Zhenyu
    Tremblay, Christine
    Muhammad, Ajmal
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Littlewood, Paul
    Belanger, Michel
    Routing and spectrum assignment in elastic filterless optical networks2016In: IEEE/ACM Transactions on Networking, ISSN 1063-6692, E-ISSN 1558-2566, Vol. 24, no 6, 3578-3592 p.Article in journal (Refereed)
    Abstract [en]

    Elastic optical networking is considered a promising candidate to improve the spectral efficiency of optical networks. One of the most important planning challenges of elastic optical networks is the NP-hard routing and spectrum assignment (RSA) problem. In this paper, we investigate offline RSA in elastic filterless optical networks, which use a passive broadcast-and-select architecture to offer network agility. Here elastic optical network is referred to as the optical network that can adapt the channel bandwidth, data rate, and transmission format for each traffic demand in order to offer maximum throughput. In elastic filterless networks, the presence of unfiltered signals resulting from the drop-and-continue node architecture must be considered as an additional constraint in the RSA problem. In this paper, first the RSA problem in elastic filterless networks is formulated by using integer linear program (ILP) to obtain optimal solutions for small networks. Due to the problem complexity, two efficient RSA heuristics are also proposed to achieve suboptimal solutions for larger networks in reasonable time. Simulation results show that significant bandwidth savings in elastic filterless networks can be achieved compared to the fixed-grid filterless solutions. The proposed approach is further tested in multi-period traffic scenarios and combined with periodical spectrum defragmentation, leading to additional improvement in spectrum utilization of elastic filterless optical networks.

  • 14.
    Cavdar, Cicek
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Ruiz, M.
    Monti, Paolo
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Velasco, L.
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Design of green optical networks with signal quality guarantee2012In: IEEE International Conference on Communications, IEEE , 2012, 3025-3030 p.Conference paper (Refereed)
    Abstract [en]

    Energy consumption of communication networks is growing very fast due to the rapidly increasing traffic demand. Consequently, design of green communication networks gained a lot of attention. In this paper we focus on optical Wavelength Division Multiplexing (WDM) networks, able to support this growing traffic demand. Several energy-aware routing and wavelength assignment (EA-RWA) techniques have been proposed for WDM networks in order to minimize their operational cost. These techniques aim at minimizing the number of active links by packing the traffic as much as possible, thus avoiding the use of lightly loaded links. As a result, EA-RWA techniques may lead to longer routes and to a high utilization on some specific links. This has a detrimental effect on the signal quality of the optical connections, i.e., lightpaths. In this study we quantify the impact of power consumption minimization on the optical signal quality. and address this problem by proposing a combined impairment and energy-aware RWA (IEA-RWA) approach. Towards this goal we developed a complete mathematical model that incorporates both linear and non-linear physical impairments together with an energy efficiency objective. The IEA-RWA problem is formulized as a Mixed Integer Linear Programming (MILP) model where both energy efficiency and signal quality considerations are jointly optimized. By comparing the proposed IEA-RWA approach with existing RWA (IA-RWA and EA-RWA) schemes, we demonstrate that our solution allows for a reduction of energy consumption close to the one obtained by EA-RWA approaches, while still guaranteeing a sufficient level of the optical signal quality.

  • 15. Cen, M.
    et al.
    Chen, J.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Moeyaert, V.
    Mégret, P.
    Wuilpart, M.
    A full monitoring scheme for long-reach TWDM PONs2015In: Asia Communications and Photonics Conference, ACPC 2015, 2015Conference paper (Refereed)
    Abstract [en]

    We propose a simple system that realizes for the first time full monitoring functionality for long-reach PON. Theoretical analysis and experimental validation demonstrate the proposed scheme is capable of providing accurate fault localization. © 2015 OSA.

  • 16. Cen, M.
    et al.
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Moeyaert, V.
    Megret, P.
    Wuilpart, M.
    Advanced Transmission-Reflection-Analysis (TRA) system for Long-Reach Passive Optical Network monitoring2015In: International Conference on Transparent Optical Networks, IEEE Computer Society, 2015, Vol. 2015, 7193394Conference paper (Refereed)
    Abstract [en]

    Long-Reach Passive Optical Networks (LR-PONs) allows for extending the distance between the central office (CO) and end users from a few kilometers to several tens of kilometers and beyond. It in turn reduces the number of active equipment in the field, bringing potentially cost saving. However, due to its high capacity and large coverage, LR-PON becomes increasingly vulnerable to various failures. Therefore, network monitoring becomes extremely important to guarantee an appropriate level of network reliability and performance. In this paper, we report on an advanced LR-PON monitoring solution that can supervise the whole LR-PON ring section in a cost-effective manner. Instead of using the conventional optical time domain reflectometry (OTDR) approach, we implement multi wavelength Transmission-Reflection Analysis (nλ-TRA) as the monitoring technique. The TRA approach is based on the unique relationship between the optical powers transmitted and backscattered by the fiber for a given loss location. Since TRA only requires measuring the power levels of monitoring signals, it outperforms other conventional methods thanks to its superior detection speed and a simple system configuration. Both experimental results have demonstrated that the proposed system can reach high accuracy for fault localization.

  • 17. Cen, M.
    et al.
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Mégret, P.
    Moeyaert, V.
    Wuilpart, M.
    Fast and simple fault monitoring for long-reach passive optical networks2014In: 2014 European Conference on Optical Communication, (ECOC), IEEE , 2014, 6964070- p.Conference paper (Refereed)
    Abstract [en]

    We propose a fast and simple monitoring system based on multi-wavelength bi-directional transmission reflection analysis approach for long-reach passive optical networks. Both experimental and simulation results have demonstrated the proposed system can reach high accuracy for fault localization.

  • 18. Cen, Min
    et al.
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Moeyaert, Veronique
    Megret, Patrice
    Wuilpart, Marc
    Advanced Fault-Monitoring Scheme for Ring-Based Long-Reach Optical Access Networks2017In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 35, no 10, 1876-1886 p.Article in journal (Refereed)
    Abstract [en]

    This paper presents a novel fiber fault-monitoring system for long-reach optical access networks based on a transmission-reflection analysis approach. By launching an un-modulated continuous-wave optical signal into the feeder ring and measuring the transmitted and reflected/backscattered optical powers, the proposed monitoring scheme is able to detect, identify, and localize any major fault (covering both reflective and nonreflective events) with a good spatial accuracy (<= 10 m) and a high detection speed (3 s). Both experimental and simulation results have demonstrated that the proposed system provides fiber monitoring functionality better than that obtained by the conventional methods.

  • 19. Cen, Min
    et al.
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab). South China Normal University, China.
    Moeyaert, Veronique
    Megret, Patrice
    Wuilpart, Marc
    Full monitoring for long-reach TWDM passive optical networks2016In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 24, no 14, 15782-15797 p.Article in journal (Refereed)
    Abstract [en]

    This paper presents a novel and simple fiber monitoring system based on multi-wavelength transmission-reflection analysis for long-reach time and wavelength division multiplexing passive optical networks. For the first time, the full localization functionality of long-reach passive optical networks is possible with the proposed monitoring scheme, including supporting fault detection, identification, and localization in both feeder and distribution fiber segments. By measuring the transmitted and reflected/backscattered optical powers launched by an unmodulated continuous-wave optical source, the proposed solution is able to supervise the network with good spatial accuracy, a high detection speed and a low impact on data traffic. Both the theoretical analysis and experimental validation show that the proposed scheme is capable of providing an accurate fault monitoring functionality for long-reach time and wavelength division multiplexing passive optical networks.

  • 20. Cen, Min
    et al.
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Moeyaert, Veronique
    Megret, Patrice
    Wuilpart, Marc
    Multi-wavelength transmission-reflection analysis for fiber monitoring2014In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 22, no 25, 31248-31262 p.Article in journal (Refereed)
    Abstract [en]

    We propose and implement a novel approach based on multi-wavelength Transmission-Reflection Analysis (MW-TRA) technique for monitoring lossy events (e.g. disconnected connectors, fiber breaks and fiber bendings) along an optical fiber link. By launching un-modulated continuous-wave lights carried by different wavelengths into the fiber and measuring their transmitted and reflected/backscattered optical powers, our proposed MW-TRA scheme is able to localize any lossy event (including both reflective and non-reflective) and to quantify the corresponding insertion and return losses with high accuracy.

  • 21. Cervero, A. G.
    et al.
    Chincoli, Michele
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Dittmann, L.
    Fischer, A.
    Garcia, A. E.
    Galán-Jiménez, J.
    Lefevre, L.
    de Meer, H.
    Monteil, T.
    Monti, Paolo
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Orgerie, A.
    Pau, L.
    Phillips, C.
    Ricciardi, S.
    Sharrock, R.
    Stolf, P.
    Trinh, T.
    Valcarenghi, L.
    Green Wired Networks2015In: Large-scale Distributed Systems and Energy Efficiency: A Holistic View, Wiley-Blackwell, 2015, 41-80 p.Chapter in book (Other academic)
    Abstract [en]

    This chapter first highlights the significant energy consumption of existing wired communication networks. It considers various means of operating such networks more efficiently. Then, the chapter examines the components that make up a wired communications network and their differing characteristics between the access and core, as well as patterns of traffic behavior. The chapter focuses on static (network planning) and dynamic (traffic-engineering) schemes that can be used to reduce the energy consumption of networks. It also pays attention to a number of challenges/open research questions that need to be resolved before the implementation of such schemes. These include issues with migration and resilience. The chapter then deals with economic-, regulatory-, and business-related methods. Finally, it focuses on the architecture of communication networks and the corresponding relationship with energy usage.

  • 22.
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Efficient resiliency mechanisms for next generation passive optical networks2013In: ICICS 2013 - Conference Guide of the 9th International Conference on Information, Communications and Signal Processing, IEEE Computer Society, 2013, 6782903- p.Conference paper (Refereed)
    Abstract [en]

    Future broadband access networks are expected to cover large service areas while fulfilling high bandwidth request on a per-user basis. The rapidly increasing traffic demand is also driven by the growing popularity of mobile data services, which is placing high-capacity requirement on the backhaul. Due to advances in wavelength division multiplexing (WDM) technology, WDM based architectures have been considered as promising candidates for next generation optical access, such as WDM passive optical network (PON), and hybrid WDM/time division multiplexing (TDM) PON. Meanwhile, resilience technique will play a more prominent role in emerging access networks due to their significantly increased capacity and coverage compared to the current deployments. Therefore, efficient resiliency mechanisms are highly required to enable uninterrupted network operation where a certain level of reliability performance can be guaranteed. In this work, we first evaluate reliability performance of each segment of next generation optical access networks and then identify the most important part for protection. A particular attention is paid to the reduction of failure impact.

  • 23.
    Chen, Jiajia
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Gong, Yu
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Fiorani, Matteo
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    High Capacity and Energy Efficient Optical Interconnects at Top of the Rack in Datacentres2014Conference paper (Refereed)
  • 24.
    Chen, Jiajia
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Gong, Yu
    Fiorani, Matteo
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Aleksic, Slavisa
    Optical Interconnects at the Top of the Rack for Energy-Efficient Data Centers2015In: IEEE Communications Magazine, ISSN 0163-6804, E-ISSN 1558-1896, Vol. 53, no 8, 140-148 p.Article in journal (Refereed)
    Abstract [en]

    The growing popularity of cloud and multimedia services is dramatically increasing the traffic volume that each data center needs to handle. This is driving the demand for highly scalable, flexible, and energy-efficient networks inside data centers, in particular for the edge tier, which requires a large number of interconnects and consumes the dominant part of the overall power. Optical fiber communication is widely recognized as the highest energy-and cost-efficient technique to offer ultra-large capacity for telecommunication networks. It has also been considered as a promising transmission technology for future data center applications. Taking into account the characteristics of the traffic generated by the servers, such as locality, multi-cast, dynamicity, and burstiness, the emphasis of the research on data center networks has to be put on architectures that leverage optical transport to the greatest possible extent. However, no feasible solution based on optical switching is available so far for handling the data center traffic at the edge tier. Therefore, apart from conventional optical switching, we investigate a completely different paradigm, passive optical interconnects, and aim to explore the possibility for optical interconnects at the top of the rack. In this article, we present three major types of passive optical interconnects and carry out a performance assessment with respect to the ability to host data center traffic, scalability, optical power budget, complexity of the required interface, cost, and energy consumption. Our results have verified that the investigated passive optical interconnects can achieve a significant reduction of power consumption and maintain cost at a similar level compared to its electronic counterpart. Furthermore, several research directions on passive optical interconnects have been pointed out for future green data centers.

  • 25.
    Chen, Jiajia
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Li, Jun
    KTH.
    Efficient Mobile Backhaul Architecture Offering Ultra-Short Latency for Handovers2016In: 2016 18TH INTERNATIONAL CONFERENCE ON TRANSPARENT OPTICAL NETWORKS (ICTON), IEEE, 2016Conference paper (Refereed)
  • 26.
    Chen, Jiajia
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Mahloo, Mozhgan
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Reducing the Impact of Failures in Next Generation Optical Access Networks2012In: 2012 Asia Communications And Photonics Conference (ACP), 2012, AS1D.2- p.Conference paper (Refereed)
    Abstract [en]

    Reliability performance of next generation optical access (NGOA) networks offering high bandwidth and large service coverage is evaluated. A particular attention is paid to the reduction of the impact of failures in NGOA.

  • 27.
    Chen, Jiajia
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Poudel, Sunil
    KTH, School of Information and Communication Technology (ICT).
    Urban, Patryk
    Fault monitoring for multi-operator and multi-service WDM PON2013In: Asia Communications and Photonics Conference, ACP 2013, Optical Society of America, 2013Conference paper (Refereed)
    Abstract [en]

    We propose fault supervision mechanisms for open WDM PON, where multiple operators could co-exist and deliver different services on a common fibre plant. The feasibility of such schemes has been validated by evaluating transmission performance.

  • 28.
    Chen, Jiajia
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Urban, P.
    Garcia, J. M.
    Cost-efficient fault supervision schemes for next generation optical access networks (invited)2014In: Asia Communications and Photonics Conference, ACP, 2014Conference paper (Refereed)
    Abstract [en]

    This paper presents different ways to implement fault monitoring technique for next generation optical access networks. A performance comparison is carried out to identify the most cost-efficient fault supervision schemes.

  • 29.
    Chen, Jiajia
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Urban, Patryk J.
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Fast fault monitoring technique for reliable WDM PON: Achieving significant operational saving2013In: 2013 Optical Fiber Communication Conference and Exposition and the National Fiber Optic Engineers Conference, OFC/NFOEC 2013, IEEE , 2013, 6532499- p.Conference paper (Refereed)
    Abstract [en]

    We propose a fast fault supervision technique compatible with an efficient resilience scheme for WDM PON. Several drop fibres can be monitored simultaneously so that a significant reduction of operational cost can be achieved.

  • 30.
    Cheng, Yuxin
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Passive Optical Top-of-Rack Interconnect for Data Center Networks2017Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Optical networks offering ultra-high capacity and low energy consumption per bit are considered as a good option to handle the rapidly growing traffic volume inside data center (DCs). However, most of the optical interconnect architectures proposed for DCs so far are mainly focused on the aggregation/core tiers of the data center networks (DCNs), while relying on the conventional top-of-rack (ToR) electronic packet switches (EPS) in the access tier. A large number of ToR switches in the current DCNs brings serious scalability limitations due to high cost and power consumption. Thus, it is important to investigate and evaluate new optical interconnects tailored for the access tier of the DCNs.

    We propose and evaluate a passive optical ToR interconnect (POTORI) architecture for the access tier. The data plane of the POTORI consists mainly of passive components to interconnect the servers within the rack as well as the interfaces toward the aggregation/core tiers. Using the passive components makes it possible to significantly reduce power consumption while achieving high reliability in a cost-efficient way.

    Meanwhile, our proposed POTORI’s control plane is based on a centralized rack controller, which is responsible for coordinating the communications among the servers in the rack. It can be reconfigured by software-defined networking (SDN) operation. A cycle-based medium access control (MAC) protocol and a dynamic bandwidth allocation (DBA) algorithm are designed for the POTORI to efficiently manage the exchange of control messages and the data transmission inside the rack.

    Simulation results show that under realistic DC traffic scenarios, the POTORI with the proposed DBA algorithm is able to achieve an average packet delay below 10 μs with the use of fast tunable optical transceivers. Moreover, we further quantify the impact of different network configuration parameters on the average packet delay. 

  • 31.
    Cheng, Yuxin
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Fiorani, Matteo
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Reliability Analysis of Interconnects at Edge Tier in Datacenters2015In: 2015 17th International Conference on Transparent Optical Networks (ICTON), Institute of Electrical and Electronics Engineers (IEEE), 2015, UNSP We.C3.1Conference paper (Refereed)
    Abstract [en]

    The growing popularity of cloud based applications is drastically increasing the traffic volume that datacenters have to handle. This brings the need for scalable, reliable, and energy-efficient interconnection networks inside the datacenters. Optical communication has been considered as a promising technology for datacenter applications due to its high energy- and cost-efficiency at ultra-high capacity. A typical datacenter interconnection network includes several tiers. Figure 1 shows an example with three tiers: edge, aggregation and core. Due to the large number of active devices on top of the rack (ToR) energy consumption at the edge tier is dominating the overall power consumed by all the switches within the datacenter [1-2]. Several passive optical interconnect approaches [2-4] have been proposed showing that replacing active optical devices by passive ones is possible to significantly reduce both the hardware cost and energy consumption, achieve lower maintenance complexity and offer a sufficient level of scalability. [GRAPHICS] Furthermore, several topologies, e.g., fat-tree [5], Quartz [6], are investigated in order to improve the resiliency and scalability, particularly for large-scale datacenters. However, it should be noted that the redundancy for these proposed topologies is often added in the aggregation and core tiers rather than the edge tier, due to the cost issue. Although passive optical ToR solution by nature could provide better reliability performance than its active counterpart, the intra-rack communication may still need survivability strategies to meet very high connection availability requirement. For instance, the required availability of fault-tolerant datacenter infrastructure (including electrical power supply, storage and distribution facilities) should be higher than 99.995% [7]. Then the expected availability for any connection established within the datacenter needs to be even higher, since the communication system is only a part of the site infrastructure. In this regard, we analyse reliability performance of optical interconnects and identify the key part to be protected. Based on it, we propose some reliable passive optical interconnects for the edge tier of the datacenter interconnection networks. They can achieve ultra-high connection availability for intra-rack communications and adapt to any topology, e.g., fat-tree and Quartz, designed to increase scalability and reliability performance for the overall datacenter network.

  • 32.
    Cheng, Yuxin
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Fiorani, Matteo
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Reliable and Cost Efficient Passive Optical Interconnects for Data Centers2015In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 19, no 11, 1913-1916 p.Article in journal (Refereed)
    Abstract [en]

    To address the sustainability, scalability, and reliability problems that data centers are currently facing, we propose three passive optical interconnect (POI) architectures on top of the rack. The evaluation results show that all three architectures offer high reliability performance (connection availability for intra-rack interconnections higher than 99.999%) in a cost-efficient way.

  • 33. Chiaraviglio, L.
    et al.
    Lorincz, J.
    Monti, Paolo
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Towards sustainable and reliable networks with LIFETEL2015In: Proceedings - IEEE INFOCOM, IEEE conference proceedings, 2015, 39-40 p.Conference paper (Refereed)
    Abstract [en]

    We present the LIFETEL project, whose aim is trying to increase the device lifetime in telecommunication networks by exploiting energy-efficient techniques. In particular, we show that the lifetime of a device might increase when it is put in sleep mode. However, the device lifetime might decrease when power state variations (from sleep mode to full power) occur very frequently. Thus, there is a trade-off between the duration of sleep mode and its frequency. Moreover, we report a lifetime analysis for cellular and backbone devices, showing that the electricity saving may be exceeded by the costs due to the fact that devices fail more frequently compared to the situation in which they are always powered on. Thus, we claim that energy-aware network algorithms should be redesigned in order not to impact and to increase (when possible) the lifetime of network devices.

  • 34. Chiaraviglio, L.
    et al.
    Wiatr, Paweł
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Monti, Paolo
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Lorincz, J.
    Idzikowski, F.
    Listanti, M.
    Impact of energy-efficient techniques on a device lifetime2014In: 2014 IEEE Online Conference on Green Communications, OnlineGreenComm 2014, IEEE conference proceedings, 2014Conference paper (Refereed)
    Abstract [en]

    This paper focuses on the impact that energyefficient techniques have on the component lifetime in optical backbone networks. The study presented in the paper considers in particular the influence that green routing strategies have on the failure rate of Erbium Doped Fiber Amplifiers (EDFAs), i.e., if their lifetime is positively or negatively impacted when putting them into sleep mode in order to reduce their energy consumption. To this end, the paper proposes a model that estimates the failure rate acceleration factor as a function of: (i) for how long and how frequently a device is switched into sleep mode, and (ii) hardware parameters that characterize the device. The proposed model is then evaluated by considering an energyefficient Routing and Wavelength Assignment (RWA) strategy that targets saving energy by putting EDFAs into sleep mode. The results presented in the paper show that energy-efficient techniques may have the potential to lower the failure rate of EDFAs. However, this is true only under specific conditions, i.e., an energy-efficient strategy needs to be carefully planned in order to avoid frequent power state transitions, which result in shortening the lifetime of an EDFA.

  • 35. Chiaraviglio, Luca
    et al.
    Wiatr, Pawel
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Monti, Paolo
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Lorincz, Josip
    Idzikowski, Filip
    Listanti, Marco
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Is Green Networking Beneficial in Terms of Device Lifetime?2015In: IEEE Communications Magazine, ISSN 0163-6804, E-ISSN 1558-1896, Vol. 53, no 5, 232-240 p.Article in journal (Refereed)
    Abstract [en]

    This article analyzes the impact that sleep mode (SM)-based green strategies have on the reliability performance of optical and cellular network elements. First, we consider a device in isolation (i. e., not plugged into a network in operation), showing how operational temperature and temperature variations, both introduced by SM, impact its lifetime. We then evaluate, from an operational cost perspective, the impact of these lifetime variations, showing that some devices are critical, that is, their achievable energy savings might not cover the potential additional reparation costs resulting from being put in SM too frequently. Moreover, we present a model for evaluating the impact of SM on the lifetime of a device plugged into an operational network. The analysis considers two case studies (one based on the optical backbone and one on cellular networks) showing that the lifetime of a device is influenced by both the hardware parameters, which depend on the specific design of the device, and the SM parameters, which instead depend on the energy-efficient algorithm used, the network topology, and the traffic variations over time. Our results show that (i) the changes in the operational temperature and the frequency of their variation are two crucial aspects to consider while designing a SM-based green strategy, and (ii) the impact of a certain SM-based strategy on the lifetime of network devices is not homogeneous (i. e., it can vary through the network).

  • 36.
    Chincoli, Michele
    et al.
    KTH, School of Information and Communication Technology (ICT).
    Valcarenghi, Luca
    Scuola Superiore Sant'Anna.
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Monti, Paolo
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Investigating the Energy Savings of Cyclic Sleep with Service Guarantees in Long Reach PONs2012In: Asia Communications and Photonics Conference, ACP, 2012, ATh1D.3- p.Conference paper (Refereed)
    Abstract [en]

    This paper evaluates what are the conditions, in terms of increased overhead time and number of optical network units (i.e., ONUs), in which cyclic sleep based techniques are effective in Long Reach PONs.

  • 37.
    Chughtai, Mohsan Niaz
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics (Closed 20120101), Photonics (Closed 20120101). KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Study of physical layer impairments in high speed optical networks2012Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The work done in this thesis focuses on the impact of transmission impairments in high speed optical networks. Specifically it focuses on the impact of nonlinear impairments in long haul fiber optic data transmission. Currently deployed fiber optic transmission networks are running on NRZ OOK modulation formats with spectral efficiency of only 1 bit/symbol. To achieve spectral efficiency beyond 1 bit/symbol, fiber optic communication systems running on advanced modulation formats such as QPSK are becoming important candidates. The practical deployment of QPSK based fiber optic communication system is severely limited by Kerr-induced nonlinear distortions such as XPM and XPolM, from the neighboring NRZ OOK channels. In this thesis we focus on the impact of nonlinear impairments (XPM and XPolM) in fiber optical transmission systems running on QPSK modulation with both differential and coherent detection. The dependence of impact of nonlinear impairments on SOP, baud rate of the neighboring NRZ OOK channels and PMD in the fiber, is analyzed in detail through numerical simulations in VPItransmission Maker®. In this thesis we also analyze digital signal processing algorithms to compensate linear and nonlinear impairments in coherent fiber optic communication systems. We propose a simplification of the existing method for joint compensation of linear and nonlinear impairments called "digital back propagation". Our method is called "weighted digital back propagation". It achieves the same performance of conventional digital back propagation with up to 80% reduction in computational complexity.In the last part of the thesis we analyze the transmission performance of a newly proposed hybrid WDM/TDM protection scheme through numerical simulation in VPItransmission Maker®. The transmission performance of the hybrid WDM/TDM PON is limited by impairments from passive optical devices and fiber optical channel.

  • 38. Colman-Meixner, C.
    et al.
    Figueiredo, G. B.
    Fiorani, Matteo
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Tornatore, M.
    Mukherjee, B.
    Resilient cloud network mapping with virtualized BBU placement for cloud-RAN2017In: 2016 IEEE International Conference on Advanced Networks and Telecommunications Systems, ANTS 2016, Institute of Electrical and Electronics Engineers (IEEE), 2017, 7947790Conference paper (Refereed)
    Abstract [en]

    Cloud Radio Access Network (C-RAN) will improve mobile radio coordination and resource efficiency by allowing baseband processing unit (BBU) functions to be virtualized and centralized, i.e., deployed in a BBU hotel. We consider a BBU hoteling scheme based on the concept of access cloud network (ACN). An ACN consists of virtualized BBUs (vBBUs) placed in metro cloud data centers (metro DCs). A vBBU is connected to a set of remote radio heads (RRHs). ACN resiliency against network and processing failures is critical for C-RAN deployments. Hence, in this study, we propose three protection approaches: 1+1 ACN protection, 1+1 ACN and vBBU protection, and partial ACN protection. Simulation results show that both 1+1 ACN and 1+1 ACN and vBBU protection requires large capacity for backup to provide 100% survivability for singlelink and single-DC failures. As a result, we suggest a partial ACN protection approach which provides degraded services with only 8% additional network resources.

  • 39.
    da Silva, Carlos Natalino
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Yayimli, Aysegul
    Istanbul University of Technology.
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Furdek, Marija
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Assessing the effects of physical layer attacks on content accessibility and latency in optical CDNs2017In: 19th International Conference on Transparent Optical Networks (ICTON), Girona, Spain: IEEE conference proceedings, 2017Conference paper (Other academic)
    Abstract [en]

    Content Delivery Networks (CDNs) are a major enabler of large-scale content distribution for Internet applications. Many of these applications require high bandwidth and low latency for a satisfactory user experience, e.g., cloud gaming, augmented reality, tactile Internet and vehicular communications. Replication is one of the most prominent solutions to meet the requirements of latency-sensitive applications. However, infrastructure disruptions can greatly degrade the performance of such applications, or even cease their proper execution. The extent of degradation can be exacerbated by malicious attackers that target the critical elements of the CDN physical infrastructure to disconnect or severely degrade services.

  • 40.
    da Silva, Carlos Natalino
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Yayimli, Aysegul
    Istanbul University of Technology.
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Furdek, Marija
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Content Accessibility in Optical Cloud Networks Under Targeted Link Cuts2017In: 2017 21st International Conference on Optical Network Design and Modeling, ONDM 2017 - Conference Proceedings, Institute of Electrical and Electronics Engineers (IEEE), 2017, 7958546Conference paper (Refereed)
    Abstract [en]

    One of the key enablers of the digital society is a highly reliable information infrastructure that can ensure resiliency to a wide range of failures and attacks. In cloud networks, replicas of various content are located at geographically distributed data centers, thus inherently enhancing cloud network reliability through diversification and redundancy of user accessibility to the content. However, cloud networks rely on optical network infrastructure which can be a target of deliberate link cuts that may cause service disruption on a massive scale. This paper investigates the dependency between the extent of damage caused by link cuts and a particular replica placement solution, as a fundamental prerequisite of resilient cloud network design that lacks systematic theoretical quantification and understanding. To quantify the vulnerability of optical cloud networks based on anycast communication to targeted link cuts, we propose a new metric called Average Content Accessibility (ACA). Using this metric, we analyze the impact of the number and the placement of content replicas on cloud network resiliency and identify the best and the worst case scenarios for networks of different sizes and connectivity. We evaluate the efficiency of simultaneous and sequential targeted link cuts, the latter reassessing link criticality between subsequent cuts to maximize disruption. Comparison with Average Two-Terminal Reliability (A2TR), an existing robustness measure for unicast networks, shows great discrepancy in the vulnerability results, indicating the need for new measures tailored to anycast-based networks.

  • 41.
    De Andrade, Marilet
    et al.
    KTH, School of Information and Communication Technology (ICT).
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Skubic, Björn
    Ahmed, Jawwad
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Enhanced IPACT: solving the over-granting problem in long-reach EPON2013In: Telecommunications Systems, ISSN 1018-4864, E-ISSN 1572-9451, Vol. 54, no 2, 137-146 p.Article in journal (Refereed)
    Abstract [en]

    In this paper we address an issue referred to as "over-granting problem", which is inherent in the existing dynamic bandwidth allocation algorithms for Ethernet-based Passive Optical Networks (EPON), in particular when deployed for multi-threaded scheme in long-reach scenario. In order to solve this problem we design a scheme for the algorithm of Interleaved Polling with Adapted Cycle Time (IPACT) with the limited service discipline. We evaluate the proposed scheme through simulations for single-thread and double-thread cases and demonstrate that, the network performance can be significantly improved by our solution in terms of average delay, jitter, and throughput.

  • 42. De Moor, K.
    et al.
    Andrén, B.
    Guo, Yi
    KTH. Acreo Swedish ICTAB, Sweden.
    Brunnström, K.
    Wang, Kun
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab). Acreo Swedish ICTAB, Sweden.
    Drott, A.
    Hermann, D.
    Influence of high ambient illuminance and display luminance on readability and subjective preference2015In: Proceedings of SPIE - The International Society for Optical Engineering, 2015Conference paper (Refereed)
    Abstract [en]

    Many devices, such as tablets, smartphones, notebooks, fixed and portable navigation systems are used on a (nearly) daily basis, both in in- and outdoor environments. It is often argued that contextual factors, such as the ambient illuminance in relation to characteristics of the display (e.g., surface treatment, screen reflectance, display luminance...) may have a strong influence on the use of such devices and corresponding user experiences. However, the current understanding of these influence factors is still rather limited. In this work, we therefore focus in particular on the impact of lighting and display luminance on readability, visual performance, subjective experience and preference. A controlled lab study (N=18) with a within-subjects design was performed to evaluate two car displays (one glossy and one matte display) in conditions that simulate bright outdoor lighting conditions. Four ambient luminance levels and three display luminance settings were combined into 7 experimental conditions. More concretely, we investigated for each display: (1) whether and how readability and visual performance varied with the different combinations of ambient luminance and display luminance and (2) whether and how they influenced the subjective experience (through self-reported valence, annoyance, visual fatigue) and preference. The results indicate a limited, yet negative influence of increased ambient luminance and reduced contrast on visual performance and readability for both displays. Similarly, we found that the self-reported valence decreases and annoyance and visual fatigue increase as the contrast ratio decreases and ambient luminance increases. Overall, the impact is clearer for the matte display than for the glossy display. © 2015 SPIE-IS&T.

  • 43. Di Giglio, A.
    et al.
    Schiano, M.
    Ruffini, M.
    Payne, D.
    Doran, N.
    Achouche, M.
    Jensen, R.
    O’Sullivan, B.
    Pfeiffer, T.
    Bonk, R.
    Rohde, H.
    Talli, G.
    Yin, X.
    Wessaly, R.
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Montalvo, J.
    Towards the distributed core for ubiquitous superfast broadband optical access2014In: 2014 European Conference on Networks and Communications (EuCNC), 2014, 1-5 p.Conference paper (Refereed)
    Abstract [en]

    In this paper, we describe recent architectural and technological advances of the end to end optical network architecture proposed by the DISCUS project (the DIStributed Core for unlimited bandwidth supply for all Users and Services). The two main targets of DISCUS are the principle of equivalence in the access and the reduction of optical-to-electronic conversions in the metro-core network. Technological advances and techno-economic evaluation of Long-Reach Passive Optical Networks (LR-PON), as well as the optimal metro-core node architecture and the required network control plane framework are reported. Network infrastructure sharing challenges are also discussed.

  • 44.
    Di Pascale, Emanuele
    et al.
    CTVR, Trinity College, Ireland .
    Payne, David B.
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Ruffini, Marco
    Locality-Aware Peer-to-Peer Multimedia Delivery Over Next-Generation Optical Networks2014In: Journal of Optical Communications and Networking, ISSN 1943-0620, E-ISSN 1943-0639, Vol. 6, no 9, 782-792 p.Article in journal (Refereed)
    Abstract [en]

    The increasing success of multimedia services poses a serious challenge to both network operators and service providers. Traditional copper-based access technologies are being replaced by fiber-to-the-X (FTTX) deployments in order to meet this increasing bandwidth demand of individual users. However, the growing traffic volume in the access segment may overload the existing aggregation part of the network, therefore creating a bandwidth bottleneck in the core. To address this problem the traffic should be kept as much as possible in the access network, taking advantage of the high-capacity fiber infrastructure. Since multimedia traffic is dominating the network, locality-aware approaches to video content distribution can represent a good solution. In this work, we propose and evaluate a network-managed, peer-to-peer based caching scheme for multimedia distribution. Our results show that such a system is able to reduce core traffic compared to the traditional content delivery network (CDN) based strategies, while at the same time decreasing the overall power consumption of the network and offering cost-saving opportunities for operators.

  • 45. Diego Cardoso, D.
    et al.
    Fiorani, Matteo
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Monti, Paolo
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Joint planning of small cells and optical transport deployment in heterogeneous mobile networks2014In: Optics InfoBase Conference Papers, OSA - The Optical Society , 2014Conference paper (Refereed)
    Abstract [en]

    We investigate how to reduce the deployment cost of heterogeneous mobile networks by joint dimensioning small cells and optical transport resources. The proposed heuristic is able to save 24% of total network deployment cost.

  • 46. Dixit, A.
    et al.
    Mahloo, Mozhgan
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Lannoo, B.
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Colle, D.
    Pickavet, M.
    Protection strategies for Next Generation Passive Optical Networks -22014In: 2014 International Conference on Optical Network Design and Modeling, 2014, 13-18 p.Conference paper (Refereed)
    Abstract [en]

    Next Generation Passive Optical Networks-2 (NG-PON2) are being considered to upgrade the current PON technology to meet the ever increasing bandwidth requirements of the end users while optimizing the network operators’ investment. Reliability performance of NG-PON2 is very important due to the extended reach and, consequently, large number of served customers per PON segment. On the other hand, the use of more complex and hence more failure prone components than in the current PON systems may degrade reliability performance of the network. Thus designing reliable NG-PON2 architectures is of a paramount importance. Moreover, for appropriately evaluating network reliability performance, new models are required. For example, the commonly used reliability parameter, i.e., connection availability, defined as the percentage of time for which a connection remains operable, doesn’t reflect the network wide reliability performance. The network operators are often more concerned about a single failure affecting a large number of customers than many uncorrelated failures disconnecting fewer customers while leading to the same average failure time. With this view, we introduce a new parameter for reliability performance evaluation, referred to as the failure impact. In this paper, we propose several reliable architectures for two important NG-PON2 candidates: wavelength division multiplexed (WDM) PON and time and wavelength division multiplexed (TWDM) PON. Furthermore, we evaluate protection coverage, availability, failure impact and cost of the proposed schemes in order to identify the most efficient protection architecture.

  • 47. Dzanko, M.
    et al.
    Furdek, Marija
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Gonzalez, N. A.
    Zervas, G.
    Mikac, B.
    Simeonidou, D.
    Experimental demonstration and benefits of self-healing hard-wired and synthetic ROADMs2014In: Optical Fiber Communication Conference, OFC 2014, Optical Society of America, 2014Conference paper (Refereed)
    Abstract [en]

    Novel hard-wired and synthetic ROADM architectures with self-healing capabilities are experimentally demonstrated. Simulation results show significant improvements of availability and recovery time due to node-level restoration, with reduced mean down time and operator revenue losses.

  • 48. Dzanko, M.
    et al.
    Furdek, Marija
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Mikac, B.
    Zervas, G.
    Hugues-Salas, E.
    Simeonidou, D.
    Synthesis, resiliency and power efficiency of function programmable optical nodes2015In: Proceedings of the 13th International Conference on Telecommunications, IEEE , 2015Conference paper (Refereed)
    Abstract [en]

    Due to the large transmibion speeds and enormous volumes of transferred data, network availability performance is one of the key ibues in optical long-haul networks, comprising nodes implemented by optical crob-connects (OXCs). In this context, the design of OXCs is becoming very challenging since they have to support both legacy lower bit-rates and future highspeed super-channels by means of flexible allocation of spectral resources, and at the same time provide high availability of established connections. In this paper we study the availability and power consumption of different node architectures. We focus on the design of the new generation of synthetic programmable OXCs based on the Architecture on Demand concept which can reduce the number of utilized node components when a certain part of signals is switched at the fibre level, resulting in lower mean down time and power consumption compared to traditional node architectures.

  • 49. Dzanko, Matija
    et al.
    Furdek, Marija
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab). University of Zagreb, Croatia.
    Zervas, Georgios
    Simeonidou, Dimitra
    Evaluating Availability of Optical Networks Based on Self-Healing Network Function Programmable ROADMs2014In: Journal of Optical Communications and Networking, ISSN 1943-0620, E-ISSN 1943-0639, Vol. 6, no 11, 974-987 p.Article in journal (Refereed)
    Abstract [en]

    Due to the large transmission speeds and enormous volume of transferred data, network reliability performance and cost-efficiency are among the key concerns in optical network design. Reducing the number of used optical components with higher failure probability within nodes represents a promising approach for achieving reliable and cost-effective optical network operation as it reduces the correlated risk of connection failures and enables reusing idle components as redundancy for failure recovery. This can result in greater overall network availability and lower loss of data and related revenue. Recently introduced synthetic network function programmable optical nodes implemented by architecture on demand (AoD) support the aforementioned approach by offering high levels of flexibility, modularity, and scalability. In AoD nodes, an optical backplane (i.e., optical switch) hosts optical components and enables arbitrary node configurations by cross-connecting attached modules. As a result, each lightpath passing through the node uses only the components necessary for fulfilling the switching and processing requirements. AoD nodes can perform switching at the wavelength and waveband granularity and also support switching of lightpaths at the fiber level by connecting an input fiber directly to the targeted output, referred to as fiber switching (FS). The latter functionality is particularly beneficial for the availability aspect, as it helps decrease the number of failure-prone components traversed by each lightpath, allowing them to be reused as redundancy. In this paper we demonstrate and evaluate self-healing capabilities of AoD nodes arising from their flexibility and ability to employ idle components for failure recovery. To improve efficiency of self-healing by increasing the number of idle components within nodes, we propose a routing algorithm which obtains a targeted portion of lightpaths switched at the fiber level, called the enforced FS (EFS) algorithm. We study the impact of AoD on network availability at different traffic switching granularities and compare it to traditional hard-wired node architecture via simulation. The results show significant improvements of availability and recovery time due to node-level restoration, with reduced network outage time and operator revenue losses. Finally, to the best of our knowledge, for the first time we experimentally demonstrate two novel hard-wired and synthetic reconfigurable optical add-drop multiplexer architectures with redundancy and all-optical self-healing capabilities.

  • 50. Dzanko, Matija
    et al.
    Mikac, Branko
    Furdek, Marija
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Dedicated path protection for optical networks based on function programmable nodes2018In: Optical Switching and Networkning Journal, ISSN 1573-4277, E-ISSN 1872-9770, Vol. 27, 79-87 p.Article in journal (Refereed)
    Abstract [en]

    Due to the constantly increasing volumes and tightening reliability requirements of network traffic, survivability is one of the key concerns in optical network design. Optical "white box" nodes based on the Architecture on Demand (AoD) paradigm allow for self-healing of nodal component failures due to their architectural flexibility and the ability to employ idle components for failure recovery. By incorporating node-level survivability with network-level protection from link failures, resiliency of optical networks can be significantly improved. To this end, we propose a survivable routing algorithm for AoD-based networks called Dedicated Path Protection with Enforced Fiber Switching (DPP-EFS), which combines self-healing at the node level with dedicated path protection at the network level. The algorithm aims at improving the self-healing capabilities of the nodes by increasing the percentage of fiber switching (FS). Namely, fiber-switched lightpaths require a minimal amount of processing within the node (i.e. only signal switching), while other aspects of processing (e.g. demultiplexing, bandwidth virtualization) and the related components (i.e. demultiplexers, splitters, wavelength selective switches) remain unused and may be used as redundancy. On the other hand, lightpaths that are not eligible for FS have to be re-routed to alternative, longer paths in order to allow for FS between certain ports within the node. Therefore, the proposed algorithm pursues an advantageous trade-off between the increase of the number of idle components which can be used as redundancy at the node level and the unwanted length increase of lightpaths re-routed to render components redundant. For particular cases when DPP-EFS is not able to reduce the mean down time (MDT) in the network merely by increasing the percentage of fiber switching, we propose an algorithm for Dedicated Path Protection with Fixed Shortest Path routing and added Redundancy (DPP-FSP-RED) which adds additional spare components at strategic nodes to ensure that all connections have at least one redundant node component along their path. Simulation results show a significant reduction in MDT with minimal extra capital expenses.

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