Showing papers in "IEEE\/OSA Journal of Optical Communications and Networking in 2009"
TL;DR: In this paper, the authors focus on minimizing the energy consumption of an IP over WDM network and develop efficient approaches ranging from mixed integer linear programming (MILP) models to heuristics.
Abstract: As the Internet expands in reach and capacity, the energy consumption of network equipment increases. To date, the cost of transmission and switching equipment has been considered to be the major barrier to growth of the Internet. But energy consumption rather than cost of the component equipment may eventually become a barrier to continued growth. Research efforts on ldquogreening the Internetrdquo have been initiated in recent years, aiming to develop energy-efficient network architectures and operational strategies so as to reduce the energy consumption of the Internet. The direct benefits of such efforts are to reduce the operational costs in the network and cut the greenhouse footprint of the network. Second, from an engineering point of view, energy efficiency will assist in reducing the thermal issues associated with heat dissipation in large data centers and switching nodes. In the present research, we concentrate on minimizing the energy consumption of an IP over WDM network. We develop efficient approaches ranging from mixed integer linear programming (MILP) models to heuristics. These approaches are based on traditional virtual-topology and traffic grooming designs. The novelty of the framework involves the definition of an energy-oriented model for the IP over WDM network, the incorporation of the physical layer issues such as energy consumption of each component and the layout of optical amplifiers in the design, etc. Extensive optimization and simulation studies indicate that the proposed energy-minimized design can significantly reduce energy consumption of the IP over WDM network, ranging from 25% to 45%. Moreover, the proposed designs can also help equalize the power consumption at each network node. This is useful for real network deployment, in which each node location may be constrained by a limited electricity power supply. Finally, it is also interesting and useful to find that an energy-efficient network design is also a cost-efficient design because of the fact that IP router ports play a dominating role in both energy consumption and network cost in the IP over WDM network.
487 citations
TL;DR: In this paper, the authors proposed a converged WDM-PON architecture for longer reach, higher data rate, and higher spectral efficiency for single-source systems and integrated the integrated schemes with radio-over-fiber (RoF)-based optical-wireless access systems to serve both fixed and mobile users in the converged optical platform.
Abstract: The wavelength-division-multiplexed passive optical network (WDM-PON) is considered to be the next evolutionary solution for a simplified and future-proofed access system that can accommodate exponential traffic growth and bandwidth-hungry new applications. WDM-PON mitigates the complicated time-sharing and power budget issues in time-division-multiplexed PON (TDM-PON) by providing virtual point-to-point optical connectivity to multiple end users through a dedicated pair of wavelengths. There are a few hurdles to overcome before WDM-PON sees widespread deployment. Several key enabling technologies for converged WDM-PON systems are demonstrated, including the techniques for longer reach, higher data rate, and higher spectral efficiency. The cost-efficient architectures are designed for single-source systems and resilient protection for traffic restoration. We also develop the integrated schemes with radio-over-fiber (RoF)-based optical-wireless access systems to serve both fixed and mobile users in the converged optical platform.
267 citations
TL;DR: The results show that implementation in optics is generally more power efficient; especially circuit-switched architectures have a low power consumption and when taking into account possible future developments of Si CMOS technology, even very large electronic packet routers having capacities of more than hundreds of terabits per second seem to be feasible.
Abstract: Power consumption and the footprint of future network elements are expected to become the main limiting factors for scaling the current architectures and approaches to capacities of hundreds of terabits or even petabits per second. Since the underlying demand for network capacity can be satisfied only by contemporaneously increasing transmission bit rate, processing speed, and switching capacity, it unavoidably will lead to increased power consumption of network nodes. On the one hand, using optical switching fabrics could relax the limitations to some extent, but large optical buffers occupy larger areas and dissipate more power than electronic ones. On the other hand, electronic technology has made fast progress during the past decade regarding reduced feature size and decreased power consumption. It is expected that this trend will continue in the future. This paper addresses power consumption issues in future high-capacity switching and routing elements and examines different architectures based on both pure packet-switched and pure circuit-switched designs by assuming either all-electronic or all-optical implementation, which can be seen as upper and lower bounds regarding power consumption. The total power consumption of a realistic and appropriate technology for future high-performance core network nodes would probably lie somewhere between those two extreme cases. Our results show that implementation in optics is generally more power efficient; especially circuit-switched architectures have a low power consumption. When taking into account possible future developments of Si CMOS technology, even very large electronic packet routers having capacities of more than hundreds of terabits per second seem to be feasible. Because circuit switching is more power efficient and easier to implement in optics than pure packet switching, the scalability limitation due to increased power consumption could be considerably relaxed when a kind of dynamic optical circuit switching is used within the core network together with an efficient flow aggregation at edge nodes.
233 citations
TL;DR: This paper quantifies the performance improvement in terms of average bit error rate (BER) and outage capacity, which are among important parameters in practice, and compares single- and multiple-aperture systems from the point of view of fading reduction.
Abstract: Atmospheric turbulence can cause a significant performance degradation in free-space optical communication systems. It is well known that the effect of turbulence can be reduced by performing aperture averaging and/or employing spatial diversity at the receiver. In this paper, we provide a synthesis on the effectiveness of these techniques under different atmospheric turbulence conditions from a telecommunication point of view. In particular, we quantify the performance improvement in terms of average bit error rate (BER) and outage capacity, which are among important parameters in practice. The efficiency of channel coding and the feasibility of exploiting time diversity in aperture averaging receivers are discussed as well. We also compare single- and multiple-aperture systems from the point of view of fading reduction by considering uncorrelated fading on adjacent apertures for the latter case. We show that when the receiver is background noise limited, the use of multiple apertures is largely preferred to a single large aperture under strong turbulence conditions. A single aperture is likely to be preferred under moderate turbulence conditions, however. When the receiver is thermal noise limited, even under strong turbulence conditions, the use of multiple apertures is interesting only when working at a very low BER. We also provide discussions on several practical issues related to system implementation.
232 citations
TL;DR: The transport network paradigm is moving toward next-generation networks that aim at IP convergence, while architectures and technologies are diversifying, and recent technical advances in these fields are presented.
Abstract: The transport network paradigm is moving toward next-generation networks that aim at IP convergence, while architectures and technologies are diversifying. Video technologies including ultrahigh-definition TV (more than 33 M pixels) continue to advance, and future communication networks will become video-centric. The inefficiencies of current IP technologies, in particular, the energy consumption and throughput limitations of IP routers, will become pressing problems. Harnessing the full power of light will resolve these problems and spur the creation of future video-centric networks. Extension of optical layer technologies and coordination with new transport protocols will be critical; hierarchical optical path technologies and optical circuit/path switching will play key roles. Recent technical advances in these fields are presented.
160 citations
TL;DR: This work investigates the impact of the nonlinear LED transfer function, i.e., the dependence of the emitted optical power on the driving current, on discrete multitone modulation.
Abstract: In the context of communications based on light-emitting diodes (LEDs), spectrally efficient modulation has been considered for overcoming their limited bandwidth, and one scheme under investigation is quadrature-amplitude modulation on discrete multitones. The dependence of the output optical power on the driving current of practical LEDs is nonlinear, which distorts the transmitted signal. We investigate the impact of the nonlinear LED transfer function, i.e., the dependence of the emitted optical power on the driving current, on discrete multitone modulation. The effect incurred by this distortion was analyzed by using detailed numerical simulations addressing the impact of clipping, individual subcarriers, signal-to-noise ratio, and bit-error ratio. The approach was generalized to describe the impact of the nonlinearity of arbitrary LEDs and laser diodes, resulting in a powerful tool for assessing the impact of the nonlinearity on the link performance. This approach was applied to three types of LED, showing anything from a minuscule effect to the case in which error-free data transmission is made impossible by the transfer-function nonlinearity.
111 citations
TL;DR: This work proposes an efficient heuristic called the Recursive Association and Relocation Algorithm (RARA) to solve the optimization problem of greenfield PON networks and can significantly reduce PON network deployment costs compared to an intuitive random-cut sectoring approach.
Abstract: We plan greenfield PON networks to minimize their total deployment costs. We propose an efficient heuristic called the Recursive Association and Relocation Algorithm (RARA) to solve the optimization problem. Our algorithm can significantly reduce PON network deployment costs compared to an intuitive random-cut sectoring approach. To further tune down the costs, we also exploit the opportunity of cable conduit sharing by proposing an extension to RARA. Our case studies show that there are saturating trends for the PON deployment costs with the increase of the three system parameters, including maximal optical split ratio, maximal transmission distance, and maximal differential distance. Also, to reduce computation time for large PON deployment scenarios, we propose a disintegration planning method to divide a large planning scenario into several small ones. The method is found to be effective to provide close performance, but require much less computation, compared to the situation without disintegration.
96 citations
TL;DR: In this article, a binary polarization shift-keying scheme with two circle polarization states, called circle polarization shift keying (CPolSK), is proposed and discussed, and the analysis of the bit-error-rate performance shows that the CPolSK system has about a 3 dB lower requirement in signalto-noise ratio than the on-off keying system.
Abstract: A binary polarization shift-keying scheme with two circle polarization states, circle polarization shift keying (CPolSK), is proposed and discussed. The propagation of the circle-polarized Gaussian Schell model beam is studied based on the cross-spectral density matrix. The results show that the state of polarization remains unchanged and the degree of polarization slightly increases upon propagation in a turbulent atmosphere. The analysis of the bit-error-rate performance shows that the CPolSK system has about a 3 dB lower requirement in signal-to-noise ratio than the on-off keying system. The modulation scheme will be helpful for practical free-space optical communication systems in the future.
90 citations
TL;DR: In this paper, both passive and active architectures integrating several multiplexing techniques are studied, and the main results for reach extension in passive optical network (PON) technologies are presented.
Abstract: We present here the main results for reach extension in passive optical network (PON) technologies. Both passive and active architectures integrating several multiplexing techniques are studied, and they provide promising results for the future generation of optical access networks. Extender boxes based on optical amplification and optical-electrical-optical (OEO) repeaters are evaluated over a standardized gigabit PON (GPON) system. With this architecture, the optical budget of a class B+ access network can be increased so as to achieve a total budget of 65 dB. Furthermore, using the technique of remotely pumped optical amplification on a wavelength division multiplexing/time division multiplexing (WDM/TDM) topology, the optical budget of a class C+ PON tree could be increased by an additional 22 dB amounting to a total budget of 55 dB. These results are promising since they should enable high flexibility on the optical budget to achieve more reach and splitting ratio, which are prerequisites needed for the migration to the next-generation access networks.
71 citations
TL;DR: In this article, the authors present multi-granular optical cross-connect (MG-OXC) architectures that combine slow (ms regime) and fast (ns regime) switch elements, in order to support optical circuit switching (OCS), optical burst switching (OBS), and even optical packet switching (OPS).
Abstract: A fundamental issue in all-optical switching is to offer efficient and cost-effective transport services for a wide range of bandwidth granularities. This paper presents multi-granular optical cross-connect (MG-OXC) architectures that combine slow (ms regime) and fast (ns regime) switch elements, in order to support optical circuit switching (OCS), optical burst switching (OBS), and even optical packet switching (OPS). The MG-OXC architectures are designed to provide a cost-effective approach, while offering the flexibility and reconfigurability to deal with dynamic requirements of different applications. All proposed MG-OXC designs are analyzed and compared in terms of dimensionality, flexibility/reconfigurability, and scalability. Furthermore, node level simulations are conducted to evaluate the performance of MG-OXCs under different traffic regimes. Finally, the feasibility of the proposed architectures is demonstrated on an application-aware, multi-bit-rate (10 and 40 Gbps), end-to-end OBS testbed.
70 citations
TL;DR: A maximum a posteriori probability (MAP) turbo equalizer based on the sliding-window multilevel Bahl-Cocke-Jelinek-Raviv algorithm is proposed, suitable for simultaneous nonlinear and linear impairment mitigation in multileVEL coded-modulation schemes with coherent detection.
Abstract: We propose a maximum a posteriori probability (MAP) turbo equalizer based on the sliding-window multilevel Bahl-Cocke-Jelinek-Raviv algorithm. This scheme is suitable for simultaneous nonlinear and linear impairment mitigation in multilevel coded-modulation schemes with coherent detection. The proposed scheme employs large-girth quasicyclic LDPC codes as channel codes. We demonstrate the efficiency of this method in dealing with fiber nonlinearities by performing Monte Carlo simulations. In addition, we provide the experimental results that demonstrate the efficiency of this method in dealing with polarization mode dispersion. We also study the ultimate channel capacity limits, assuming an independent identically distributed source.
TL;DR: In this article, the authors present a sensible scheduling algorithm for inter-metropolitan-area-network (inter-MAN) OFS communication and an analytical approximation of the throughput-delay trade-off offered by OFS for interMAN communication.
Abstract: In our previous work [Chan, ldquoOptical flow switching,rdquo in BROADNETS 2006, pp. 1-8; Weichenberg, ldquoCost-efficient optical network architectures,rdquo in ECOC 2006, pp. 1-2; Weichenberg, ldquoOn the throughput-cost tradeoff of multi-tiered optical network architectures,rdquo GLOBECOM '06, pp. 1-6], we presented optical flow switching (OFS) as a key enabler of scalable future optical networks. We now address the design and analysis of OFS networks in a more comprehensive fashion. The contributions of this work, in particular, are in providing partial answers to the questions of how OFS networks can be implemented, how well they perform, and how their economics compare with those of other architectures. With respect to implementation, we present a sensible scheduling algorithm for inter-metropolitan-area-network (inter-MAN) OFS communication. Our performance study builds upon our work in IEEE J. Sel. Areas Commun., vol. 25, no. 6, pp. 84-101, 2007 and Weichenberg, ldquoPerformance analysis of optical flow switching,rdquo presented at the IEEE International Conference on Communications, Dresden, Germany, June 14-18, 2009, and includes a comparative capacity analysis for the wide area, as well as an analytical approximation of the throughput-delay trade-off offered by OFS for inter-MAN communication. Last, with regard to the economics of OFS, we extend our previous work from ECOC 2006 and GLOBECOM '06 in carrying out an optimized throughput-cost comparison of OFS with other prominent candidate architectures. Our conclusions indicate that OFS offers a significant advantage over other architectures in economic scalability. In particular, for sufficiently heavy traffic, OFS handles large transactions at far lower cost than other optical network architectures. In light of the increasing importance of large transactions to communication networks, we conclude that OFS may be crucial to the future viability of optical networking.
TL;DR: A novel polling algorithm to increase resource utilization by partitioning ONUs into two subgroups with some overlap is proposed, which both defers saturation points of queues in ONUs and provides outstanding network throughput compared with previous work.
Abstract: The Ethernet passive optical network (EPON) is an emerging technology for the next-generation broadband access networks and is considered an up-to-date candidate network for future fiber to the home. A crucial issue in EPONs is the sharing of uplink bandwidth among optical network units (ONUs). To manage resources efficiently, research on polling schemes based on multipoint control protocol has been conducted. We propose a novel polling algorithm to increase resource utilization by partitioning ONUs into two subgroups with some overlap. In the proposed scheme, after receiving frames from ONUs in one subgroup, the OLT performs dynamic bandwidth allocation for ONUs in the other. Hence, the OLT continuously receives frames from ONUs without significant interruptions. Comprehensive computer simulation results show that the proposed algorithm both defers saturation points of queues in ONUs and provides outstanding network throughput compared with previous work. It has up to 45% lower average packet delay and maximum performance improvement of 17% with respect to network throughput.
TL;DR: This work considers the use of a classic binary convolutional code together with iterative soft demodulation and channel decoding at the receiver of pulse position modulation and provides design rules for optimal mapping in the case of MPPM.
Abstract: Signal modulation has an important impact on the system performance in optical communication. Two attractive modulation schemes are pulse position modulation (PPM) and multipulse PPM (MPPM), which have the advantage of average energy efficiency and bandwidth efficiency, respectively. An important practical issue is to employ an efficient channel coding of reasonable (decoding) complexity adapted to these modulations. In this view, we consider the use of a classic binary convolutional code together with iterative soft demodulation and channel decoding at the receiver. In particular, we discuss the impact of bit-symbol mapping on the iterative receiver performance and provide design rules for optimal mapping in the case of MPPM.
TL;DR: This work designs a capacity- and delay-aware routing scheme, called CaDAR, for WOBAN that can support much higher load and has lower system delay than other approaches because of better load-balanced routing.
Abstract: A wireless-optical broadband access network (WOBAN) is a combination of wireless and optical network segments to optimize the cost and performance of an access network. A WOBAN's optical backhaul enables it to support high capacity, while its wireless front end [also called a wireless mesh network (WMN)] enables its users to have untethered access. Wireless nodes collect traffic from end users and carry them to the optical part of a WOBAN, possibly using multiple hops, but the traffic also experiences delay at each wireless node. The finite radio capacity at each wireless node limits the capacity on each outgoing link from a wireless node of a WOBAN. Thus, delay and capacity limitation in the WMN of a WOBAN are major constraints. We design a capacity- and delay-aware routing scheme, called CaDAR, to minimize the delay and increase the throughput in the WMN of a WOBAN. Our analysis shows that CaDAR is an efficient routing scheme for WOBAN that can support much higher load and has lower system delay than other approaches (IEEE Network, vol. 22, no. 3, p. 20, 2008) because of better load-balanced routing.
TL;DR: It is identified that the realization of colorless optical network units (ONUs) is an important technical issue for both applications, and an effective protection function is another important issue, especially for the long-reach WDM-PON.
Abstract: We review our recent research activities on the applications and technical issues of WDM passive optical networks (WDM-PONs). First, we describe our focus on two candidate applications of WDM-PON: one is a long-reach WDM-PON based on wavelength routing for metro-access integration, and the other is a short-reach WDM-PON for coexistence with current PON systems. We identify that the realization of colorless optical network units (ONUs) is an important technical issue for both applications, and an effective protection function is another important issue, especially for the long-reach WDM-PON. We compare several colorless-ONU approaches as well as introduce our recent research results to resolve the issues raised by some colorless-ONU approaches. We also describe two demonstrations: one is the long-reach WDM-PON with a wavelength-shifted protection scheme as well as loop-back-type colorless ONUs, and the other is a WDM-PON coexisting with a current PON system with tunable-type colorless ONUs.
TL;DR: The performance of diversity coherent and incoherent receivers in the presence of fading, background noise, and various interference types is investigated and it is found that diversity coherent detection provides significant power gain over diversity direct detection and that most of the benefit of Diversity coherent detection can be achieved with a small amount of diversity.
Abstract: When communicating optically through the clear atmospheric channel, not only is there atmospheric turbulence and background noise, but there may also be interference from other sources such as other users in a multiple access system. Even if the interference is off axis, its signal can couple into the receiver through scattering. We would like our communication system to perform well in the presence of interference, background noise, and fading. This paper investigates the performance of diversity coherent and incoherent receivers in the presence of fading, background noise, and various interference types. We find that diversity coherent detection provides significant power gain over diversity direct detection and that most of the benefit of diversity coherent detection can be achieved with a small amount of diversity. Moreover, we find that diversity always improves the performance of coherent detection, whereas in the presence of worst-case interference, diversity degrades the performance of direct detection. This paper also describes a sensible way to select the amount of diversity and power margin to deal with atmospheric turbulence and interference and quantifies the amount of interference that the system can handle while still achieving a given outage probability.
TL;DR: The BRPC algorithm and the companion PCE protocol are extended in order to address the end-to-end WCC efficiently and a quantitative comparative analysis of the different approaches is performed, experimentally showing the improvements of the conceived solution.
Abstract: In the context of the future Internet, all-optical wavelength switched optical networks will play an important role in either evolutionary or revolutionary design paradigms. In any paradigm, dense wavelength domain multiplexing (DWDM) is the most cost-effective technology to increase bandwidth capacity. DWDM provides the basis for a core optical transport infrastructure supporting a wide range of heterogeneous services. However, such all-optical networks raise well-known challenges such as the wavelength continuity constraint (WCC). The WCC is hard to address in a multiarea scenario when provisioning an end-to-end lightpath owing to network topology hiding requirements and the limited exchange of information between areas. The Internet Engineering Task Force (IETF) is currently standardizing the path computation element (PCE) architecture, a good candidate to perform multidomain path computation. In such an architecture, the approach named backwards recursive path computation (BRPC), also under standardization at the IETF, aims at overcoming the limitations of the per-domain mechanism. However, although BRPC does provide end-to-end shortest paths, it fails to take into account the WCC, which is the main motivation for this work. We extend the BRPC algorithm and the companion PCE protocol in order to address the end-to-end WCC efficiently. We perform a quantitative comparative analysis of the different approaches, experimentally showing the improvements of the conceived solution, which has been evaluated in a GMPLS-controlled network of the ADRENALINE testbed.
TL;DR: This work attempts to lift the veil of next-generation WDM PON topologies and optical network unit architectures while paying close attention to their smooth evolutionary migration path from current TDM PONs.
Abstract: After discussing point-to-point fiber-to-the-home, WDM passive optical networks (PONs), and multistage WDM PON networks and elaborating on their respective advantages and limitations, I attempt to lift the veil of next-generation WDM PON topologies and optical network unit architectures while paying close attention to their smooth evolutionary migration path from current TDM PONs. I introduce optical coding enhanced WDM PONs that allow for enhanced real-time dynamic bandwidth allocation and outline future research avenues.
TL;DR: In this article, different wavelength division multiplexing passive optical network (WDM-PON) architectures compatible with pre-existing gigabit PON (GPON) infrastructures are presented and critically discussed.
Abstract: In this paper we present and critically discuss different wavelength division multiplexing passive optical network (WDM-PON) architectures compatible with pre-existing gigabit PON (GPON) infrastructures. The concurrent use of the trunk fiber permits a hitless evolution from an existing time division multiplexing optical access network to a point-to-point wavelength division access network. System performance has been experimentally evaluated in terms of bit error rate.
TL;DR: A scalable integrated design for the sliding scheduling provisioning problem (SSPP) is proposed, based on the Lagrangean relaxation (LR) approach, which can jointly perform the scheduling and RWA of the demands.
Abstract: Many future Internet applications supported over optical networks may require large amounts of guaranteed bandwidth between two remote end hosts, but this bandwidth may not necessarily be needed immediately. To ensure a deterministic service, Internet customers may prefer to reserve network resources, e.g., lightpaths, in advance and may indicate an approximate time window in the future during which the bandwidth should be reserved for a certain period of time; however, the exact start time of the reservation is not specified, but can slide in the predefined time window. This type of user traffic is called ldquosliding scheduled traffic.rdquo Optical network design for provisioning sliding scheduled traffic is a highly complex task that has been dealt with in the literature by two-step approaches, which first schedule user demands in time and then perform their routing and wavelength assignment (RWA). We propose a scalable integrated design for the sliding scheduling provisioning problem (SSPP), based on the Lagrangean relaxation (LR) approach, which can jointly perform the scheduling and RWA of the demands. We first develop a new mathematical model for SSPP, to which it is suitable to apply the relaxation of some of the modelpsilas constraints. We use an integrated heuristic called IPSR (integrated provisioning of sliding requests), which is next enhanced with a cost assignment based on Lagrangean multiplier information, to serve as the primal algorithm for our LR approach (named IPSR-LR). We compare our approaches with an existing two-step heuristic algorithm for SSPP and show that both IPSR and IPSR-LR are able to outperform it. In addition, our numerical results show that IPSR-LR improves over IPSR under all typical experimental cases that we considered. Furthermore, we compare our approaches with the solutions provided by an integer linear program for the SSPP, which is, however, less scalable for large problem sizes compared with our algorithms.
TL;DR: This work analyzes the use of optical fabrics to interconnect line cards in terabit packet switches and routers and shows that aggregate capacities of the order of a few terabits per second are possible in very simple optical switching fabrics and that the multiplane architectures permit a complexity trade-off between the wavelength and space domains, making the overall design more feasible.
Abstract: The design of fabrics for terabit packet switches and routers needs to consider the limitations imposed by electronic technologies. In particular, attention has to be paid to information density and to power consumption and dissipation, as well as to power supply and footprint requirements. Optical technologies can overcome some of these limitations. We analyze the use of optical fabrics to interconnect line cards in terabit packet switches and routers. For this purpose, single-plane and multiplane optical interconnection architectures are proposed that exploit wavelength agility at line cards to implement the required switching functionality. The physical-layer scalability and feasibility of these architectures are studied by using realistic models, mostly based on the characteristics of commercially available optoelectronic devices. As a result, the considered architectures can be characterized in terms of power budget and signal-to-noise ratio, enabling the computation of the maximum achievable port count and aggregate switching capacity. Our results show that aggregate capacities of the order of a few terabits per second are possible in very simple optical switching fabrics and that the multiplane architectures permit a complexity trade-off between the wavelength and space domains, making the overall design more feasible.
TL;DR: This work presents a hybrid ring-shaped wavelength division multiplexing (WDM)-time division multipleXing (TDM) passive optical network (PON) that is capable of providing bandwidth on demand at high bit rates in a transparent and dynamic manner.
Abstract: The intensification of traffic in the access network requires the development of novel architectural solutions for a reconfigurable network topology and components based on optical technologies. We present a hybrid ring-shaped wavelength division multiplexing (WDM)-time division multiplexing (TDM) passive optical network (PON) that is capable of providing bandwidth on demand at high bit rates in a transparent and dynamic manner. Our cost-efficient and scalable network architecture is based on integratable components such as a wavelength-agile optical networking unit and a microring-resonator-based remote node. An appropriately modified control layer is introduced to manage the network. We also discuss the implementation of optical codes instead of time slots to take the step toward optical code division multiplexing (OCDM) WDM PONs that relieve the network of strict time scheduling of traffic and ranging. Therefore, an additional reduction of complexity in network management, improvement of network scalability, and a guarantee of fully symmetric traffic are foreseen for every user. Finally, we show a scenario for smooth migration from existing PON solutions to our WDM-TDM PON architecture.
TL;DR: This paper presents techniques used to virtualize and manage optical networks in order to have services decoupled from the underlying infrastructure while especially focusing on its impact on next-generation optical networks.
Abstract: Current network operators are focused mainly on providing and selling network services on top of the network infrastructures they own and manage. The end user has no control over how these services are provided. However, specific requirements are coming from emerging applications that request network and computational resources. These new requirements are difficult to accommodate with the existing telecommunication operational models because telecom companies have full control over the infrastructure. However, through virtualization, it is possible to allocate isolated instances from networking devices to different users or applications. This paper presents techniques used to virtualize and manage optical networks in order to have services decoupled from the underlying infrastructure while especially focusing on its impact on next-generation optical networks. Moreover, benefits from using this approach are demonstrated in terms of network operation, emerging services, and industry impacts. Actually, the main rationale behind optical network virtualization is the capability to offer infrastructure services to end users by exposing control of the infrastructure to the end users, allowing them themselves to assemble networks. We also present how the ldquoinfrastructure as a servicerdquo (IaaS) concept brings a new role to infrastructure providers as it allows the deployment of dynamic services in optical networks and the federation of their underlying infrastructures.
TL;DR: In this paper, the role of bufferless optical packet switches (OPSs) realized in semiconductor optical amplifier (SOA) technology in reducing average power consumption has been analyzed for high capacity electronic routers.
Abstract: Increase in data transmission and processing speed unavoidably leads to high requirements on power supply. Especially in the case of high- capacity electronic routers, the question of power consumption will be the major issue and probably the most important limiting factor for the future. This paper analyzes the role of bufferless optical packet switches (OPSs) realized in semiconductor optical amplifier (SOA) technology in reducing average power consumption. An analytical model is proposed to provide an expression for the average power consumption of bufferless OPSs as a function of both the offered traffic and the main parameters characterizing the power consumption of the space switching modules (SSMs) and wavelength converters (WCs) needed to realize the bufferless OPSs. The effectiveness of WC sharing, which reduces the average power consumed by WCs, is evaluated in the case in which the Tucker's model for the evaluation of the power consumed by the SSMs and WCs is used. The obtained results show that, due to the high power consumed by the switching elements, switches with shared WCs may require average power consumption higher than switches in which WC sharing is not performed. In particular, only when the offered traffic is low and high-energy-consumption WCs are used, is the WCs sharing effective. When cross-gain modulation WCs are employed, the sharing technique allows for a reduction of average power consumption from 50% to 10% when the offered traffic is varying from 0.1 to 0.9. To obtain more realistic power consumption of the bufferless OPSs, we have introduced in our analytical model some power consumption values evaluated and experimentally validated for the SOAs produced by some manufacture's and needed to realize the SSMs and WCs. In this case we compare the power consumed of the bufferless OPSs to that of a Cisco GSR 12008 router equipped with ten slots that can accommodate up to 4 Gb/s per slot and designed for operation in a network core. We take into account for comparison the power consumption normalized to the offered total input bit rate.
TL;DR: The proposed fault model is general and may be applied to any fault-tolerance scenario (e.g., some nodes/links/region only) and is revealed to make an efficient reuse of spectrum under different fault-Tolerance scenarios.
Abstract: The wirelessߝoptical broadband-access network (WOBAN) architecture has been proposed as a flexible and cost-effective solution for future access networks. However, for WOBANs to provide geographically continuous wireless coverage it is necessary to integrate fault tolerance in the design of such networks. At the optical back end, multiple failures, having different impact levels, may be addressed (e.g., optical network unit, optical line terminal). At the wireless front end, the disruption of connections, or throughput speed decrease on user's devices, can be a consequence of unlicensed spectrum utilization, where the radio band is common to different systems. We address the problem of planning a fault-tolerant multiradio WOBAN while using resources efficiently. The proposed fault model is general and may be applied to any fault-tolerance scenario (e.g., some nodes/links/region only). The adopted approach is revealed to make an efficient reuse of spectrum under different fault-tolerance scenarios.
TL;DR: In this paper, the authors proposed a coded modulation scheme suitable for beyond 100 Gb#s transmission and 100Gb#s Ethernet, which is based on polarization multiplexed coded-orthogonal frequency division multiplexing (OFDM) and achieves a spectral efficiency of 10 bits#s#Hz.
Abstract: We propose a coded-modulation scheme suitable for beyond 100 Gb#s transmission and 100 Gb#s Ethernet. It is based on polarization multiplexed coded-orthogonal frequency division multiplexing (OFDM). By using 32-QAM-based polarization multiplexed coded-OFDM, we are able to achieve the aggregate rate of 100 Gb#s, while the OFDM signal bandwidth is only 10 GHz, resulting in a spectral efficiency of 10 bits#s#Hz. The spectral efficiency of the proposed scheme is twice higher than that of the polarization diversity OFDM scheme. We show that the proposed multicarrier scheme is insensitive to polarization mode dispersion (PMD), while the PMD represents a major source of performance degradation in single carrier systems, in addition to fiber nonlinearities. We also describe how to determine the symbols' log-likelihood ratios in the presence of laser phase noise.
TL;DR: In this paper, the authors proposed a new optical double-sideband modulation technique that is immune to fiber chromatic dispersion and thus free of dispersion-induced RF power fading.
Abstract: We propose and demonstrate a new optical double-sideband modulation technique that is immune to fiber chromatic dispersion and thus free of dispersion-induced RF power fading. The proposed modulation technique also provides a 3 dB improvement of RF power compared with optical single-sideband modulation. The proposed modulation technique is analyzed in theory and simulation. It is shown that for a given fiber length an optimum electrical phase shift exists to completely cancel the dispersion-induced RF power fading. We verify this proposed modulation technique experimentally for a single-tone RF signal and for a multiband orthogonal frequency division multiplexing ultrawideband signal.
TL;DR: This work presents a novel bandwidth scheduling scheme that integrates specific scheduling implementations in the optical line terminal and optical network units that enables multiservice access with scalable quality of service support for the triple-play services and open access.
Abstract: Dynamic bandwidth allocation (DBA) is one of the key issues for the current (1G) and next-generation (10G) Ethernet-based passive optical network (EPON) systems. We present a novel bandwidth scheduling scheme that integrates specific scheduling implementations in the optical line terminal and optical network units. This scheduling enables multiservice access with scalable quality of service support for the triple-play (video, voice, and data) services and open access. Our simulation results show that the proposed scheduling algorithm performs very well in supporting service differentiation and fair allocation of bandwidth to different service providers. A performance comparison between 1G and 10G systems is also presented. To the best of our knowledge, no detailed study of DBA in a 10G EPON can be found in the literature so far.
TL;DR: A new type of virtualized optical substrate architecture is proposed that utilizes optical orthogonal frequency division multiple access (OFDMA), along with subwavelength switching and generic packet routing to realize the network bandwidth programmability.
Abstract: To meet diverse, bandwidth-intensive applications envisioned in future optical networks, as well as address the shortcomings of the current Internet, novel networking technologies will be of great importance. We discuss several key issues for the future Internet, including network virtualization mechanisms, a programmable network architecture, parallelism of optical transmission, and guaranteed quality of service provisioning. Moreover, a new type of virtualized optical substrate architecture is proposed that utilizes optical orthogonal frequency division multiple access (OFDMA), along with subwavelength switching and generic packet routing to realize the network bandwidth programmability. The main features, benefits, and design and implementation challenges of optical OFDMA networking based on sliceable routers are also described. Finally, an adaptive subcarrier allocation and assignment algorithm for future OFDMA-based networking is investigated, and a performance comparison between the proposed approach and legacy time division multiple access (TDMA)-based techniques is drawn.