Optical transport network

This paper studies the overall energy consumption of a pan-European optical transport network for three different time periods: today and in five and ten years from now. In each time period the pan-European network was dimensioned using traffic predictions based on realistic data generated by the optical networking roadmap developed in the framework of the European project Building the Future Optical Network in Europe-BONE. A wavelength routed wavelength division multiplexed optical network based on either ...

The explosive growth of data-traffic, for example due to the popularity of the Internet, poses important emerging network requirements on today's telecommunication networks. This paper describes how core networks will evolve to Optical Transport Networks (OTNs), which are optimised for the transport of data-traffic, resulting in a IP-directly-over-OTN paradigm.

An overview of commercially available large-scale photonic integrated circuits (PICs) in indium phosphide is provided. Results of 100-Gb/s PICs that are field-deployed in wavelength-division-multiplexing (WDM) networks is provided, along with development results showing scaling of both channel count and channel bit rate to implement next-generation PICs with an aggregate capacity of 1.6 Tb/s. Use of PIC-enabled WDM systems allows affordable optical-electrical-optical (OEO) conversion and the implementation of "digital" optical networks with enhanced sub-wavelength reconfigurable bandwidth management, digital performance monitoring, and protection features. PICs will enable the continued capacity scaling required for next-generation IP core networks and support of high-bandwith 40-G and 100-GbE service connectivity between core routers.

Legacy ring-based networks have been deployed in conjunction with SONET/SDH technology to provide survivability to transport networks, and they achieve service recovery within 50 ms after fault detection. Current generalized multiprotocol label switching (GMPLS)-controlled optical transport networks need efficient resilience mechanisms to allow recovery times equivalent to those granted by SONET/SDH networks. In this paper, dedicated and shared optical multiplex section (OMS) protection systems are proposed. Both solutions consist of a mechanism based on extensions of the GMPLS link management protocol (LMP) to properly manage the protection actions, and both utilize a new reconfigurable optical add/drop multiplexer (ROADM) design to support the protection schemes. The performance of both solutions has been experimentally evaluated.

The evaluation and reduction of energy consumption of backbone telecommunication networks has been a popular subject of academic research for the last decade. A critical parameter in these studies is the power consumption of the individual network devices. It appears that across different studies, a wide range of power values for similar equipment is used. This is a result of the scattered and limited availability of power values for optical multilayer network equipment. We propose reference power consumption values for Internet protocol/multiprotocol label switching (IP/MPLS), Ethernet, optical transport networking (OTN) and wavelength division multiplexing (WDM) equipment. In addition we present a simplified analytical power consumption model that can be used for large networks where simulation is computationally expensive or unfeasible. For illustration and evaluation purpose, we apply both calculation approaches to a case study, which includes an optical bypass scenario. Our results show that the analytical model approximates the simulation result to over 90% or higher, and that optical bypass potentially can save up to 50% of power over a non-bypass scenario.

Abstract—This paper presents the results of the optical packet switched network (OPSnet) project, which investigated the de-sign of an asynchronous optical packet switch suitable for the core of an optical transport network (OTN). The requirements for the switch were to ...

We address the problem of generating physical realistic optical transport network topologies. This type of network has characteristics that differ from scale-free networks, such as the Internet. Based on the analysis of a set of real transport topologies, we identify and assess relevant characteristics. A method to generate realistic topologies is proposed. The proposed method is validated by comparing the characteristics of computer-generated and real-world optical transport networks.

Legacy ring based networks have been deployed in conjunction with SONET/SDH technology to provide survivability to transport networks. Service recovery within 50ms after fault detection can be achieved. With the advent of optical transport networks provided with GMPLS control plane, efficient resilience mechanism have to be investigated to provide recovery times equivalent to those granted by SONET/SDH networks. In this paper a Reconfigurable Optical Add and Drop Multiplexer (ROADM) design to support dedicated section protection (OMS-DPRing) scheme is described. Using these new ROADMs in conjunction with proposed extensions to GMPLS Link Management Protocol (LMP) will allow achieve recovery times equivalent to those granted by SONET/SDH architectures. 1

Optical transport networks with automatic switching capabilities (ASON, Automatic Switching Optical Networks) appear as a potential solution to cope with the increasingly growth of Internet traffic demands. This paper focuses in the context of the ASON control plane. In this context, an Optical NNI (O-NNI) has to be defined. For some time it seemed clear that such an O-NNI would

An important requirement in the IP-based control of time-division multiplexing (TDM) optical transport networks is to utilize the in-built protection capabilities of synchronous optical network (SONET) unidirectional path-switched rings (UPSRs) and to automate the UPSR-...

In this paper we study different options for the survivability implementation in MPLS over Optical Transport Networks (OTN) in terms of network resource usage and configuration cost. We investigate two approaches to the survivability deployment: single layer and multilayer survivability and present various methods for spare capacity allocation (SCA) to reroute disrupted traffic.

Abstract—Integrated circuits for very high-speed telecommu-nication protocols often use ASICs, due to their strict timing constraints. This scenario is changing, since modern FPGAs, implemented in 65 or 45 nm technologies achieve high operating frequencies, and serializer/deserializer hardwired modules enable the reception of high speed aggregated rates (e. g. 10 Gbps or more), spanning the input stream for internal parallel computation. This paper presents a complete solution for an Optical Transport Network framer using FPGA devices. The framer receives a 10 Gbps stream originated from optical fiber medium, extracts its payload information, and transmits payload data at 10 Gbps. A working prototype was implemented in Virtex-4 and Virtex-5 devices. (Abstract) Keywords-FPGA, OTN (Optical Transport Network), Telecommunication Circuits, Framer (key words) I.

Integrated circuits for very high-speed telecommunication protocols often use ASICs, due to their strict timing constraints. This scenario is changing, since modern FPGAs, implemented in 65 or 45 nm technologies achieve high operating frequencies, and serializer/deserializer hardwired modules enable the reception of high speed aggregated rates (e. g. 10 Gbps or more), spanning the input stream for internal parallel computation. This paper presents a complete solution for an Optical Transport Network framer using FPGA devices. The framer receives a 10 Gbps stream originated from optical fiber medium, extracts its payload information, and transmits payload data at 10 Gbps. A working prototype was implemented in Virtex-4 and Virtex-5 devices. (Abstract)

Both the OIF and IETF inter-domain interfaces for control plane enabled networks are based on GMPLS protocols. OIF interfaces include ITU-T/ASON specific extensions, resulting in interoperability issues. Moreover, the connection services considered by the OIF are focused on SONET/SDH, OTN (i.e., G.709) and Ethernet, but do not consider lambda services for all-optical transport networks (i.e., without O/E/O conversion) as supported by GMPLS. Previous interoperability experiences are based on implementing an ASON-GMPLS gateway at the edge nodes in order to have the same inter-domain interface between domain edges. Regarding to the LSC switching, it is addressed introducing proprietary extensions to OIF interfaces allowing to request Lambda services. This paper presents a protocol-unaware solution for enabling seamless interworking based on a centralized ASON-GMPLS proxy transparent for domain edges. Experimental demonstration has been performed in the integrated NOBEL2 Pan-European control plane emulator.

Given the abundance and strategic importance of ring fiber-plants in metropolitan area networks, and the accelerating growth of Internet traffic, it is crucial to make use of recent advances in optical networking technologies such as WDM, ROADMs, OXCs and tunable transceivers in order to offer the most cost-efficient traffic transport. The objective of this paper is to present the metropolitan all-optical tuneable AWG-based R-OADM ring network implemented in the ADRENALINE testbed.

The prospects of optical burst switching (OBS) as a cost-effective switching paradigm for future all-optical transport networks would greatly benefit from minimizing the number of wavelength converters required at the network nodes. This paper presents a wavelength assignment framework tailored for OBS networks with shared wavelength converters directed to reach this aim. Simulation results using a reference network show that the performance attained with full-range dedicated wavelength converters can be achieved with less than half the number of these converters if shared converters are used instead. Moreover, it is shown that the number of converters can be further decreased by employing the proposed wavelength assignment framework. The extent of this decrease depends on the offered traffic load and the number of wavelengths per link.

This contribution deals with the RWA (routing and wavelength assignment) in semi-transparent optical networks. In semi-transparent networks, a parameter called Maximum Transmission Distance (MTD) is used to indicate the distance reachable in wavelength continuity. When for a given lightpath, the signal cannot be detected at the destination node a regenerator has to be installed in an intermediate node. The regenerator breaks up the optical continuity and the optical network becomes a semi-transparent optical network. The new RWA mechanism proposed in this paper will take into account the physical impairment such as the Maximum Transmission Distance (MTD). Moreover this new RWA algorithm will be based on the Prediction-Based Routing (PBR) mechanism and will take into account the routing inaccuracy problem. The goal of the proposed algorithm will be both, to reduce the number of blocked connections due to the routing inaccuracy problem and to select routes that fulfil the MTD physical impairment. On the other hand, transparent optical networks do not convert the signal to the electrical domain in the intermediate nodes but rather keep the signal in the optical domain from source to destination. Full transparency is not however always achievable in long distance networks, due to the degradation an optical signal accumulates in propagation. In semi-transparent optical networks regenerators are employed when the quality of the signal falls below the level required for an acceptably correct detection.

Carrier Ethernet exhibits an enormous potential to be a cost-effective and less complex replacement of SONET/SDH especially after the ratification of IEEE standard 802.1Qay Provider Backbone Bridge-Traffic Engineering (PBB-TE). The recent IEEE standard 802.3az Energy Efficient Ethernet (EEE) presents another opportunity for service providers to select Ethernet as a technology of choice in the backbone while leveraging on its promise for achieving green transport network. In this paper, we propose two novel architectures of photonic PBB-TE core and edge switches, which enhance the usability of PBB-TE networks by reducing power consumption in individual switches in conjunction with passive optical bypassing and EEE. We also formulate the problem of energy-aware scheduling as an optimization problem whose objective is to minimize the overall energy consumption for transmitting Ethernet frames while satisfying their delay requirements. This model will be used as a benchmark while evaluating the performance of packet coalescing, a promising and recently proposed approach, as well as the performance of EEE.

In wavelength-routed optical networks, the high-delay introduced by the optical switching fabric for resource reservation increases critically the lightpath setup delay. In order to minimize the setup delay, Generalized Multi-protocol Label Switching (GMPLS) introduced the concept of Suggested Label Object (SL), which allows to start reserving and configuring the hardware with a proposed wavelength from the source node to the destination node. This solution is not optimal in wavelength selective networks (WSN) (i.e., without wavelengths converters). The need of guaranteeing the wavelength continuity constraint for end-to-end optical connections, combined with the lack of global wavelength-based link information (the source node is not aware of which wavelengths are available on each link), makes that the likelihood of establishing a lightpath using the proposed suggested label may be minimum. In this article, we propose an enhancement to the current GMPLS RSVP-TE signaling protocol with offset time-based provisioning that minimizes the lightpath setup, improving the overall network performance in terms of blocking probability and setup delay. Experimental performance evaluation has been carried out in ADRENALINE testbed, a GMPLS-based intelligent all-optical transport network.

In this paper we study different options for the survivability implementation in MPLS over Optical Transport Networks (OTN) in terms of network resource usage and configuration cost. We investigate two approaches to the survivability deployment: single layer and multilayer survivability and present various methods for spare capacity allocation (SCA) to reroute disrupted traffic.

Although the automatically switched optical networks (ASON) specifications strongly recommend a hierarchical network architecture for these networks, this is still an open issue. The hierarchical network concept involves several mechanisms mainly related with signaling and routing, such as the aggregation scheme, the dissemination process, the updating policy and the routing algorithms. The existing mechanisms for flat networks must be substantially modified to be applied to a hierarchical network architecture. In this paper, authors propose a complete hierarchical routing approach mainly focusing on routing concerns, aiming to optimize the global network performance while guaranteeing scalability.

Remarkable technological progress has been made in the development of Optical Transport Networks during the past decade. An optical transport network is a digital signal transport plarform which provides jexible and powerful signal transmission capabilities needed to create telecommunication services networks. This paper highlights the key technologies required for the development of optical transport networks; optical jiber transmission, and digital transport which includes transmission signal multiplexing, transport nodes, and network operation functions. The trends in transport technology evolution, the impact of SDH and ATM, the role of TMN (Telecommunications Management Networks), and network integrity enhancement techniques are elucidated. It is demonstrated that these technologies have brought about a dramatic change in transport network design and performance. Further innovations are required to fully realize a high-performance computer communication network, a cost-effective nationwide BISDN, and local networks for video distribution. These include the realization of an optical access transport network, and the extension of trunk network capabilities which will be possible with optical path layer technologies.

Exploiting inverse-multiplexing in optical transport networks (OTN) leads to a cost-effective network design based on legacy 10 Gbps or 40 Gbps equipment to support next-generation services, e.g., 100 Gbps Ethernet. The inclusion of multipath routing permits to better balance the load and avoid problematic capacity bottlenecks. However, with diverse-path routing the inverse-multiplexed connections may arrive at the destination node with differential delay. Such effect needs to be mitigated by buffering the early-arriving connections until synchronization is achieved and the original signal can be adequately reconstructed. One of the main design issues on inverse-multiplexed networking consists in routing the demands in such way that the buffer sizes are minimized and the load balancing maximized. In this context, centralized or distributed solutions may be adopted. The latter option considers that buffering at intermediate path nodes results in smaller buffer dimensions per node. However, existing literature in this topic has systematically neglected the limited availability of expensive optical-to-electrical and electrical-to-optical converters necessary to buffer the transit signals. OTN architectures typically dispose of such elements when signal regeneration is performed. Hence, it makes sense to promote the buffering-regeneration collocation to limit network expenditures. For this reason, this work proposes a set of integer linear programming formulations for planning OTN networks using inverse-multiplexed traffic in a scenario where the distribution of the differential delay compensation takes into account the presence of regeneration equipment. As a result, we observe that our methodologies are capable of reaching a satisfactory compromise by minimizing the regenerator count while attaining small buffer sizes.

IP-based backbone networks are gradually moving to a network model consisting of high-speed routers that are flexibly interconnected by a mesh of light paths set up by an optical transport network that consists of wavelength division multiplexing (WDM) links and optical cross-connects. In such a model, the generalized MPLS protocol suite could provide the IP centric control plane component that will be used to deliver rapid and dynamic circuit provisioning of end-to-end optical light paths between the routers. This is called an automatic switched optical (transport) network (ASON). An ASON enables reconfiguration of the logical IP topology by setting up and tearing down light paths. This allows to up- or downgrade link capacities during a router failure to the capacities needed by the new routing of the affected traffic. Such survivability against (single) IP router failures is cost-effective, as capacity to the IP layer can be provided flexibly when necessary. We present and investigate a logical topology optimization problem that minimizes the total amount or cost of the needed resources (interfaces, wavelengths, WDM line-systems, amplifiers, etc.) in both the IP and the optical layer. A novel optimization aspect in this problem is the possibility, as a result of the ASON, to reuse the physical resources (like interface cards and WDM line-systems) over the different network states (the failure-free and all the router failure scenarios). We devised a simple optimization strategy to investigate the cost of the ASON approach and compare it with other schemes that survive single router failures.

Stimulated by the remarkable packet traffic growth, the transport of 100 Gb/s Ethernet (100-GbE) services is to become a reality in a near future. To provide a smooth and costefficient network evolution, inverse-multiplexing techniques can be employed to carry the high-capacity data streams. In this context, the Virtual Concatenation (VCAT) protocol, available in Optical Transport Network (OTN) systems, represents the most adequate solution to decompose the 100-GbE signal into logical containers of 10 Gb/s and 40 Gb/s. With VCAT, each container can be independently routed throughout the network under several distribution paradigms, such as the classical single-path and multipath schemes, and the alternative degraded-service approach. In the network architecture considered, each routing path is required to be transmitted over an optical channel at the underlying WDM layer. Hence, in this work, we provide an optimization framework for solving the resource provisioning problem for 100-GbE at both OTN and WDM layers. Linear Programming based heuristics are proposed for routing the containers and dimension the capacity required at the OTN level. In particular, solutions for single-path, multipath, and degradedservice routing are described and evaluated in a reference network topology. The optimization procedures are also extended to resolve the wavelength assignment problem at the physical WDM layer. With this optimized multilayer architecture, the capacity gains resulting from the adoption of multipath strategies over single-path are properly evaluated and demonstrated. In addition, it is shown that the implications of using diverserouting over the WDM layer have a minor impact in the capacity savings.

In this paper we study different options for the survivability implementation in MPLS over Optical Transport Networks (OTN) in terms of network resource usage and configuration cost. We investigate two approaches to the survivability deployment: single layer and multilayer survivability and present various methods for spare capacity allocation (SCA) to reroute disrupted traffic. The comparative analysis shows the influence of the traffic granularity on the survivability cost: for high bandwidth LSPs, close to the optical channel capacity, the multilayer survivability outperforms the single layer one, whereas for low bandwidth LSPs the single layer survivability is more cost-efficient. For the multilayer survivability we demonstrate that by mapping efficiently the spare capacity of the MPLS layer onto the resources of the optical layer one can achieve up to 22% savings in the total configuration cost and up to 37% in the optical layer cost. Further savings (up to 9 %) in the wavelength use can be obtained with the integrated approach to network configuration over the sequential one, however, at the increase in the optimization problem complexity. These results are based on a cost model with actual technology pricing and were obtained for networks targeted to a nationwide coverage.

Optical Transport Network (OTN) is a standard approach to offering transport support to a variety of existing service technologies, e.g., ESCON, HDTV, GE, etc. Multiple service technologies can be concurrently multiplexed onto one common transport network, which offers hierarchical transmis- sion rate wrappers physically supported by Wavelength Division Multiplexing (WDM) lambda channels. Algorithms to perform grooming and routing in OTN

In this work, we analyzed by means of numerical and laboratory experiments the resilience of 40 Gb/s amplitude shift keying modulation formats to transmission impairments in standard single-mode fiber lines as well as to optical filtering introduced by the optical add/drop multiplexer cascade. Our study is a pre-requisite to assess the implementation of costeffective 40 Gb/s modulation technology in next generation high bit-rate robust optical transport networks.

Aiming at better resource utilization, an important requirement of future optical transport networks is the capability to accommodate subwavelength client flows efficiently. This can be put into action thanks to the enhanced traffic engineering (TE) protocols provided within the generalized multiprotocol label switching (GMPLS) standardization. The present paper concentrates on the design and implementation of a GMPLS-controlled grooming-capable transport infrastructure, namely, the automatically switched optical network (ASON)ÕGMPLS CARISMA test bed. Through the paper, the operation of a GMPLS-controlled multilayer network architecture is introduced, subsequently highlighting implementation issues that come to light. Special attention is devoted to a centralized flow reallocation module deployed in the CARISMA test bed to minimize the overall network cost. In this context, an integer linear programming (ILP) formulation to obtain its optimal cost is derived and low-weighted metaheuristics providing a nearly optimal solution are additionally proposed. All contributions in the paper are supported by illustrative experimental results.

The experimental demonstration of MOSAIC, a reconfigurable WDM add/drop network with subcarrier multiplexed control, is presented. The MOSAIC network implements the optical layer protocol to support bit-rate transparent multichannel lightpaths. Two types of add/drop multiplexers are implemented and combined in a three-node experiment. Multihop lightpaths are established giving an end-to-end bit error rate of better than 10 0 0 09 at 1.2 Gbps. The reconfigurable add/drop multiplexer is based on a novel dilated 2 2 2 2 2 acoustooptic filter switch crossconnect and an analog optoelectronic crossconnect that drives a ten-wavelength laser array transmitter up to 2.5 Gbps per wavelength. The fixed wavelength add/drop multiplexer utilizes a fast digitally tunable laser transmitter. Both add/drop multiplexers support bit-rate transparent 2R optoelectronic regeneration as well as wavelength translation. Subcarrier multiplexing on each wavelength is used to support channel state monitoring and channel equalization as well as transmission of digital network control information. Systems experiments demonstrate cascaded 2R optoelectronic regeneration with wavelength translation and cascaded multichannel optical switching with up to seven hops. It is shown that combining cascaded 2R optoelectronic regeneration with cascaded multichannnel optical switching can be used to balance jitter accumulation and amplified spontaneous emission generated amplitude noise to yield high signal-to-noise ratio for lightpaths.

Remote provisioning of a nonblocking reconfigurable multichannel wavelength-division-multiplexed add-drop multiplexer (ADM) is experimentally demonstrated. The ADM add/drop multiplexer supports many features required by the ITU optical channel layer including lightpath routing, signal conditioning and network/channel monitoring. Specifically, the node supports multichannel optical bypass and add/drop functions as well as optoelectronic 2R regeneration and channel drop-andcontinue with wavelength translation. Provisioning of a slave node from a remote master node is achieved via a subcarrier encoded control channel. The control channel can set the full state of the ADM and demonstration of switching between two states is reported. A reconfiguration time of the order of 10 s and BER below 10 09 are shown in both configurations.

The emergence of new telematic applications and services is creating significant growth in the traffic carried over the optical transport network (OTN). One potential cost-effective approach for satisfying these demands consists in applying inverse-multiplexing techniques, such as virtual concatenation (VCAT). In this context, efficient load balancing can be achieved by exploiting multipath routing at the cost of introducing differential delay in the concatenated circuits. This effect can be compensated through appropriate delay compensation techniques (e.g., electrical buffering), which can act either in a centralized way with the buffering at the end nodes, or by distributing the differential delay throughout the intermediate nodes. In order to properly solve the routing and differential delay compensation distribution problem in the OTN, we propose two novel methods: a dual-step integer linear programming (ILP) model and a tabu search multi-stage heuristic. These strategies are compared with our two former proposals consisting of a single-step ILP model and an iterative search heuristic. The four solutions are further expanded to consider the possibility of using homogeneous or heterogeneous VCAT. The performance of these optimization methods is examined in two network topologies assuming that 100 Gb/s Ethernet streams are carried over 40 Gb/s channels (homogeneous case) or over a mixed combination of 40 Gb/s and 10 Gb/s channels (heterogeneous case) in the OTN. The results obtained show that, as expected, the smallest buffering requirements are obtained by both ILP models, with the dual-step version exhibiting also a significant reduction in the number of optical-to-electrical and electrical-to-optical operations used for intermediate compensation. In addition, the novel tabu search framework is able to surpass our former heuristic by simultaneously leveraging minimum link capacities and reducing the buffer sizes.

Pan-European WDM optical transport networks (OTN), as the supporting infrastructure for the push toward an “information society” will require new levels of management and supervision to ensure the quality of payload delivery. Several European funded projects such as MEPHISTO and MOON have addressed the needs for WDM-OTN Management Systems Support, proposing layered management object information models as a standard. This

Pan-European WDM optical transport networks (OTN), as the supporting infrastructure for the push toward an “information society” will require new levels of management and supervision to ensure the quality of payload delivery. Several European funded projects such as MEPHISTO and MOON have addressed the needs for WDM-OTN Management Systems Support, proposing layered management object information models as a standard. This

We analyze the shortest path lengths between node pairs of real optical transport networks (OTNs). From the analysis, we find that Johnson SB distribution is suitable for the shortest path length modeling. The validity of the distributions is evaluated in terms of the Kolmogorov-Smirnov (KS) statistic. Johnson SB distribution provides an average KS statistic of 0.0423, which indicates its good accuracy. We also show that the key parameters of the shortest path lengths, such as the mean, the median, and the standard deviation, can be estimated from the convex area of the network. We develop the proposed Johnson SB distribution model for the shortest path lengths using the basic information of the networks. The developed model is able to estimate path-length dependent system parameters, such as the appropriate modulation formats in transparent optical networks with an average error of only 6.4%. It is noteworthy that these estimations can be made without full knowledge of the network. Only the node locations are required. Index Terms-Shortest path lengths of network; optical transport network; average shortest path length; statistics of shortest path lengths; distribution of shortest path lengths.

One of the most debatable issues in the field of optical networks is wavelength conversion. With the introduction of the multi-granular switching concept, the debate can be extended to consider the signifieance of performing label conversion for all optical flows defined in Generalized Multiprotocol Label Switching (GMPLS). In order to conduct this study, we compare heuristics that are developed specifically to plan large-scale GMPLS-based transport network with and without the labelconversion capability. The simulation results show that label conversions can be quite beneficial especially when fiber resources are scarce and the network physical connectivity is high.