Optical network

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

The work presents a structural and functional model of a distributed low level radio frequency (LLRF) control system for the TESLA-XFEL accelerator. The design of a system basing on the FPGA chips and multi-gigabit optical network was debated. The system design approach was fully parametric. The major emphasis is put on the methods of the functional and hardware concentration to use fully both: a very big transmission capacity of the optical fiber telemetric channels and very big processing power of the latest series of the, DSP enhanced and optical I/O equipped, FPGA chips. The subject of the work is the design of a universal, laboratory module of the LLRF sub-system. Initial parameters of the system model under the design are presented

We propose a novel graph model for multiplexing optimization in optical networks and evaluate the performance of several multiplexing policies. Simulation shows that our advocated multiplexing policy can provide significant network cost savings.

A simple all-optical logic device, composed of an SOA and an optical filter, is proposed. By utilising optical filtering, multi-logic functions (AND, OR and XOR) are demonstrated at 10 Gbit=s using the same setup, under different operation conditions. Simulations indicate that the device can operate at much higher bit rate.

A multi-channel wavelength division multiplexed (WDM) transmission system using non-degenerate fourwave mixing (FWM) in a semiconductor optical amplifier (SOA) with spectrum-sliced ASE inputs from a single LED high powered incoherent source is presented. Three incoherent ASE inputs generate twelve SOA output channels, nine of which are FWM generated, and all are modulated at 10 Gb/s after the FWM process to avoid phase-noise limitations. SOA input power saturation characteristics were investigated and eye diagram analysis confirms high-quality transmission for each FWM channel, with an average achievable link length of 63.9 km, proving the validity of the scheme. By decoupling carrier generation from data encoding, this post-FWM architecture enables clean performance despite incoherent seeds, offering a low-cost, scalable solution for WDM in access and metro networks and wavelength conversion if required.

The study outlined the soliton pulse order effects on the performance efficiency of the optical transceiver systems. The power after fiber is reported for various Soliton pulse order. Max optical signal power (SP) and min optical noise power (NP) are clarified versus time after optical fiber for various soliton pulse order. As well as the max electrical power amplitude against time period is demonstrated after electrical filter for various soliton pulse order. It is reported that the optical transceiver performance efficiency can be upgraded with the first soliton order pulse. The soliton technique is used for high speed communication transmission systems. Soliton technique is used to compensate the dispersion and balanced with nonlinear effects. The soliton order effects is then discussed to choose the suitable soliton order for high speed system performance efficiency. The soliton techniques can be used also for extended ultra high transmion distance with high data rates.

Designing virtual topologies is necessary to obtain maximum performance of optical networks. In this paper the routing and wavelength assignation (RWA) is computed using an elitist team of multiobjective evolutionary algorithms, which proposes converting the original RWA problem into a problem of traditional routing, thereby modifying the graph that represents the optical network. The Elitist Team Algorithm simultaneously minimizes the total hop count and the total number of wavelengths for a set of given unicast demands. In this way, a set of optimal solutions, known as a Pareto set, is calculated in only one run of the algorithms without a priori restrictions.

Yufeng Xin. Topology Design of Large-Scale Optical Networks. (Under the direction of Professor George N. Rouskas and Professor Harry G. Perros). Optical networks consisting of optical cross-connects(OXCs) arranged in some arbitrary topology are emerging as an integral part of the Internet infrastructure. The main functionality of these networks will be to provide reliable end-to-end lightpath connections to large numbers of electronic label switched routers (LSRs). We consider two problems that arise in building such networks. The first problem is related to the topology design of optical networks that can grow to Internet scales, while the second is related to the light-tree routing for the provision of optical multicast services.

With the increase of the number of wavelengths per fiber waveband switching has been proposed to decrease the number of switching ports in optical nodes. Another concept that of Light trails, allows the intermediate nodes along a lightpath to access the wavelength channel, aiming at the reduction of the number of wavelengths. Both techniques apply traffic grooming on different levels of the WDM network. In this paper, we combine them and compare the two switching techniques: waveband switching lightpath (WBS-LP) and waveband switching lighttrail (WBS-LT). Auxiliary graph models (LP_AG/LT_AG) are proposed for WBS-LP/WBS-LT respectively. These two auxiliary graph models can exploit not only the wavelength resource in the fiber links but also the limited waveband ports resource inside the multi-granular optical cross connects (MG-OXC) nodes. The influence of network parameters, e.g. number of wavebands, ports and transceivers, is studied. The proposed algorithms are compared with shortest path (SP), leastweighted path (LW), and K-least-weighted path (KP) algorithms; numerical simulations show their better performance. For different algorithms, WBS-LT can have better blocking performance than WBS-LP especially when add/drop waveband ports are the critical resources.

Wavelength Division Multiplexing(WDM) technology enables a lightpath to carry tens of gigabits of data per second. However, many applications may require an optical connection for only short periods of time, and leasing a lightpath full time for that purpose may be too costly. We consider a single WDM link that is time shared by a given collection of optical connections. The system is time slotted with period T. Each optical connection has a prescribed duration per time period. In addition, it has a prescribed time window within which its duration may begin. The size of the window is the amount of time flexibility there is to schedule the optical connection. The problem considered is to set up the optical connections. Formulas are provided to show the relationship between wavelength efficiency and the "burstiness" and time flexibility of the connections. In addition, a few heuristic algorithms are presented that perform better than simple scheduling rules of a packet-switched network, under simulations for randomly generated optical connections.

Many results exist in the literature describing technological and theoretical advances in optical network topologies and design. However, an essential e ort has yet to be done in linking those results together. In this paper, we propose a step in this direction, by giving optical layouts for several graph-theoretical topologies studied in the literature, using the Optical Transpose Interconnection System (OTIS) architecture. These topologies include the family of Partitioned Optical Passive Star (POPS) and stack-Kautz networks as well as a generalization of the Kautz and de Bruijn digraphs.

In an optical network using the wavelength division multiplexing (WDM) technology, routing a request consists of assigning it a route in the physical network and a wavelength. If each request uses 1/g of the bandwidth of the wavelength, we will say that the grooming factor is g. That means that on a given edge of the network we can groom (group) at most g requests on the same wavelength. With this constraint the objective can be either to minimize the number of wavelengths (related to the transmission cost) or minimize the number of Add/Drop Multiplexers (shortly ADM ) used in the network (related to the cost of the nodes). Here, we first survey the main theoretical results obtained for different grooming

Many results exist in the literature describing technological and theoretical advances in optical network topologies and design. However, an essential e ort has yet to be done in linking those results together. In this paper, we propose a step in this direction, by giving optical layouts for several graph-theoretical topologies studied in the literature, using the Optical Transpose Interconnection System (OTIS) architecture. These topologies include the family of Partitioned Optical Passive Star (POPS) and stack-Kautz networks as well as a generalization of the Kautz and de Bruijn digraphs.

We consider the problem of graph discovery in settings where the graph topology is known, while the edge weights are hidden. The setting consists of a weighted graph G with n vertices and m edges, and with designated source s and destination t. We study two different discovery problems; namely, (i) edge weight discovery, where the goal is to discover all edge weights, and (ii) shortest-path discovery, where the goal is to discover a shortest (s, t)-path. This discovery is done by means of agents that traverse different (s, t)-paths in multiple rounds and report back the total cost they incurred. Three cost models are considered, differing from each other in their approach to congestion effects. In particular, we consider congestion-free models as well as models with positive and negative congestion effects. We seek bounds on the number of rounds and the number of agents required to complete the edge-weights or the shortest-path discovery. A number of results concerning such bounds for both directed and undirected graphs are established. Among these results, we show that: (1) for undirected graphs, all edge weights can be discovered within a single round consisting of m agents; (2) discovering a shortest path in either undirected or directed acyclic graphs requires at least m -n + 1 agents; and (3) the edge weights in a directed acyclic graph can be discovered in m rounds with m + n -2 agents under congestion-aware cost models. Our study introduces a new setting of graph discovery under uncertainty and provides fundamental understanding of the problem.

We present the results of a study of the performance of InGaAs detectors conducted for the SuperNova Acceleration Probe (SNAP) dark energy mission concept. Low temperature data from a nominal 1.7um cut-off wavelength 1kx1k InGaAs photodiode array, hybridized to a Rockwell H1RG multiplexer suggest that InGaAs detector performance is comparable to those of existing 1.7um cut-off HgCdTe arrays. Advances in 1.7um HgCdTe dark current and noise initiated by the SNAP detector research and development program makes it the baseline detector technology for SNAP. However, the results presented herein suggest that existing InGaAs technology is a suitable alternative for other future astronomy applications.

T not be used for new multimedia applications. Ncw tcchnologies and new standards arc necessary to offer quality of service (QoS) for thcse multimedia applications. Therefore, new communication architectures integrate mechanisms allowing guarantees of specific quality to services as well as high data rates for communication systcms. This fcaturc topic in IEEE Communications Magazine seeks to survey and present the research and engineering work currently ongoing in the field of QoS. Quality of service must be seen as an end-to-end process. Assume, for examplc, that you want to establish a video conferencing over the Internet using the UMTS (the third-generation Universal Mobilc Tclccommunication Systcm) as thc access network for your communications. At the two vcry cndpoints of this communications process we have the end-user terminals (e.g., a ccllular phonc at one cnd and a desktop computcr conncctcd to the wircd Internet at the other). Thc access tcchnology hcrc thus compriscs several systems: the local bearer service providing the service to the cellular phone user, the UMTS bearer scrvicc, and thc cxtcrnal bcarcr scrvice providing service to the desktop user. Without the support of the required QoS indicators (e.g., delay and bandwidth in our current example) by all segments of the network from cnd to end, we cannot claim we have QoS support. UMTS has its own share in providing QoS, but thc cndpoint bcarcr serviccs also nccd to support similar QoS indicators in order to complete the end-to-end process. Although it is possible to provide QoS with different ways of support by the individual segments in the network, it will be much more efficient and reliable to providc QoS with closc interrelation between the individual segments. The Intcrnct Engineering Task Force (IETF) started working on providing the QoS in IP networks in the mid 1990s. Two diffcrcnt approachcs havc bccn introduccd: integrated services (IntServ) in 1994 and differentiated services (Diff-Serv) in 1998. IntScrv was introduccd in IP networks in ordcr to provide guaranteed and Controlled services in addition to the already available best-effort service. It is an extension to the Intcrnct architccture to support both non-real-time and real-time applications over IP. Each traffic flow in this service can be classificd under one of three service classes: guaranteed, controlled load, and bcst cffort. Guaranteed service provides delay-bounded service agreements for voice and other real-time applications requiring severe delay constraints. Controlled load scrvice provides a form of statistical delay service agreement (e.g., with a nomi-

We report on the generation of combined FSK/IM modulation format by using GCSR tunable laser sources. FSK modulation, up to 100 Mbit/s, has been achieved by modulating the phase section of a GCSR laser source. We experimentally demonstrate generation of combined FSK/IM modulation at 100Mbit/s and 10 Gbit/s, respectively. We also report on successful FSK label insertion using a SOA-MZI wavelength converter.

We analyze here a pure greedy hot-potato routing strategy on a two-dimensional mesh of n2 nodes. We specifically study the case of n2 packets, originating one per node, to be delivered at random uniform destinations. Each packet attempts to follow the shortest path leading first to the destination row/column (whichever is closest) and then to the actual destination node. A deflection policy ia adopted to solve conflicts. We prove that all packets are delivered to the destinations in average time O(nlogn). The average is taken over all possible destination functions. No average case analysis of pure greedy hot-potato routing was known up to now.

Output Queuing (OQ) and Input Queuing (IQ) are the two basic queuing strategies implemented in routers. IQ has been identified as the simplest and the most scalable. However, IQ achieves only 58.6% throughput due to the Head Of Line (HOL) blocking effect. The Virtual Output Queuing (VOQ) strategy is a proffered solution to the HOL blocking. It has been shown that VOQ can achieve a 100% throughput with an effective scheduling algorithm. This paper proposes a Multi stage Queuing and Scheduling strategy which implements VOQ at the input and OQ at the output of the router. The scheduling algorithm for the VOQ proposed in this paper is an Iterative Probabilistic Scheduling.

The deployment of more economical and cost-effective wavelength division multiplexing (WDM) solutions for access and metro networks still remains a key research focus. This paper reports on significant performance enhancement improvements of a highly economical, four channel totally incoherent spectrum-sliced WDM system with the incorporation of a Semiconductor Optical Amplifier (SOA) placed in one of its channels. The baseline system was shown to operate well at 10 Gb/s at a maximum link length of 210 km, demonstrating average Q-factor and signal-to-noise ratios (SNRS) over the four channels. However, the introduction of a single saturated SOA and a single filter placed on one channel yielded a sizable improvement in the Q-factor and exceptional improvement in the measured signal-to-noise ratio (SNR), effectively allowing a further 130 km link travel length whilst still yielding acceptable signal qualitymaking a total link length of 340 km for one channel.

QoS-based routing has been recognized as a missing piece in the evolution of QoS-based service offerings in the Internet. In this paper, MPLS (Multiprotocol Label Switching) is used for forwarding packets over the backbone, and Constraint-based Routing and enhanced link state IGP (Interior Gateway Protocols) is used for distributing routes over the backbone. The primary goal of this method is to provide Qos-based routing and a background for Traffic Engineering in IP backbone services for enterprise networks. We then discuss the general issues of designing an MPLS system in an Internet Service Provider’s (ISP) network. Putting these together, we present the readers the practical issues of Traffic Engineering and a working solution for Traffic Engineering with MPLS in the Internet

Statistical multiplexing at the optical layer has been considered a critical requirement in order to build the next generation of ultra-high capacity optical transport networks in a cost-efficient manner. However, even today, the state of the art of commercially available optical core networks is based on mature wavelength switching and routing technologies, which lack a transport and control plane architecture that can support statistical traffic multiplexing with guaranteed Quality of Service (QoS) across a wide range of QoS parameters even if they can support fast reconfiguration at msec time scales. For several years, most research efforts have focused on the concepts of Optical Burst Switching (OBS) and Optical Packet Switching (OPS), which are based on the hybrid use of electronic nodes and optical switches to exploit Time Division Multiplexing (TDM) in order to achieve statistical multiplexing and dynamic resource reservation over optical networks. While burst switching has b...

In this work we benchmark through appropriate performance metrics the legacy Optical Circuit Switching (OCS) mode in an optical network of nodes following a mesh topology interconnection vs. a clustered optical network architecture (CANON). The results demonstrate that the static reservation of WDM channels, as used in IP/WDM schemes, is severely limiting scalability, since it cannot efficiently adapt to the dynamic traffic fluctuations that are frequently observed in today's networks, while the hierarchical clustered architecture with dynamic reservations can exploit statistical multiplexing efficient grooming traffic at appropriate granularity levels leading to improved performance and resource utilization. We quantify through computer simulation the performance gains and the smoothing of traffic profile achieved when implementing the CANON architecture as an upgrade of existing infrastructure by using the reference network of a European operator. The effect of traffic grooming, when employing CANON and its impact on performance and cost are evaluated using a national backbone network as a case study.

Today's core networks deploy Wavelength Division Multiplexing (WDM) to offer high capacity of the order of 1 Tb/sec and long reach transmission of the order of 1000 km. In such systems, the information is transmitted optically on different wavelengths but it is transferred across the network through fibre links that are terminated by SONET/SDH equipment. In such networks, layer crossing is inevitable, requiring deep data inspection and complex protocol processing, resulting in limited scalability and high installation, operation and maintenance cost. It is however the only reliable end-to-end service delivery scenario available today that utilises the optical bandwidth and guarantees provisioning of resources. In this paper we review the alternative concept of CANON (Clustered Architecture for Nodes in Optical Networks), a scenario that utilises clustering of nodes in ring topologies to create a hierarchy in transporting traffic in a dynamic, future proof and scalable manner. Here we emphasize on the optical crossconnect architectures that can serve such a network scenario.

The lack of effective contention resolution mechanisms in the optical domain presents dynamic optical switching architectures with a hard dilemma between high loss (when adopting one-way reservations) and high delay (when using two-way reservations). In this work we evaluate an alternative hierarchical network architecture, which achieves a satisfactory compromise by partitioning the network into a number of geographically limited domains operating in slot and frame synchronous mode where two-way reservations are effective.

On the wavelength-division multiplexing (WDM) optical networks, when the num-ber of wavelengths for realizing a set R of routing requests is beyond the number of wavelengths supported by an optical link, multiple rounds of routing for R are required. R = {(u, v)} is a set of multicasts if each source u sends a message to at least one destina-tion v and each destination v receives a message from exactly one source u. In this paper, we propose routing algorithms for a set of multicasts on n-dimensional WDM all-optical butterfly networks. For a network with wavelength converters, we give algorithms which realize any set of multicasts by 2 (n-1)/(k+1) wavelengths in k rounds of routing. For k = 1, the upper bound is tight to the lower bound.

This paper deals with the insertion of a dedicated path protection strategy in the design of a novel optical network structure, called PetaWeb, that can reach a total capacity of several Pb/s (10 15 bit/s). Prior studies of the same authors have tackled the optimization of a PetaWeb network architecture with a regular composite-star topology and with a quasi-regular topology. In this paper, a protection strategy is added to the network model modifying the optimization algorithm. The results show that the optimized PetaWeb architecture is reliable and that every edge node is connected to at least two switching sites. We highlight the strength of the proposed network model for this composite-star architecture: a fast-switching backbone that eases signaling and switching operations at a competitive network cost. The network cost is evaluated on real physical costs and on a virtual cost due to lightpaths propagation delays.

As client demands grow, optical network operators are required to introduce lightpaths of higher line rates in order to groom more demand into their network capacity. For a given fiber network and a given set of client demands, the minimum cost network design is the task of assigning routing paths and wavelengths for a minimum cost set of lightpaths able to groom all client demands. The variant of the optical network design problem addressed in this paper considers a transparent optical network, single hop grooming, client demands of a single interface type, and lightpaths of two line rates. We discuss two slightly different mixed integer linear programming models that define the network design problem combining grooming, routing, and wavelength assignment. Then, we propose a parameters increase rule and three types of additional constraints that, when applied to the previous models, make their linear relaxation solutions closer to the integer solutions. Finally, we use the resulting models to derive a hybrid heuristic method, which combines a relax-andfix approach with an integer linear programming-based local search approach. We present the computational results showing that the proposed heuristic method is able to find solutions with cost values very close to the optimal ones for a real nationwide network and considering a realistic fiber link capacity of 80 wavelengths. Moreover, when compared with other approaches used in the problem variants close to the one addressed here, our heuristic is shown to compute solutions, on average, with better cost values and/or in shorter runtimes.

With regard to digital services access, many rural and remote urban area in developing countries are underserved, if served at all. In a monopolized environment, telecommunications are of low quality and costly. Broadband Internet and other digital services are restricted to small percentage of people. In some cases the operator prefers to pay fines instead of providing services to remote areas. In this paper we present an infrastructure together with its business model that is being installed in the Brazilian Ceara state. This infrastructure was entirely constructed by the state government, but the operational costs (OPEX) will be paid by investors willing to share data transportation. Different groups will be chosen among interested investors by public auction, in order to enforce competition. Moreover, a new state company will be created that will offer low cost data transportation services, assuring that high bandwidth will be available to more than 80% of the state population.

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.