Optical Transport Network

About: Optical Transport Network is a research topic. Over the lifetime, 6055 publications have been published within this topic receiving 85783 citations.

Optical free-space wavelength-division-multiplexing transport system

Abstract: An optical free-space wavelength-division-multiplexing (WDM) transport system employing vertical cavity surface emitting lasers and spatial light modulators with 16-quadrature amplitude modulation orthogonal frequency-division multiplexing modulating signals over a 17.5 m free-space link is proposed and demonstrated. With the help of a low-noise amplifier and data comparator, good bit error rate performance is obtained for each optical channel. Such an optical free-space WDM transport system would be attractive for providing services including data and telecommunication services.

Optimization problems in WDM optical transport networks with scheduled lightpath demands

Abstract: Wavelength division multiplexing optical transport networks are expected to provide the capacity required to satisfy the growing demand of telecommunications traffic in a cost-effective way. These networks, based on standards and implementation agreements currently under development by the ITU-T, the IETF and the OIF, are likely to be deployed during the next 5 or 6 years. New optimization problems arise in connection with these networks for several reasons. Firstly, the cost of optical networking equipment is not still well known due mainly to the early stage of development of the relevant technologies. Secondly, the uncertainty of traffic demands, due to the competition in the telecommunications market and to the massive adoption of new data applications, render difficult the accurate dimensioning of networks. Finally, the early stage of development of optical technology results in new functional constraints that must be taken into account during the design and dimensioning of the network. We investigate optimization problems arising in the engineering of an optical transport network. Network engineering concerns the configuration of existing network resources in order to satisfy expected traffic demands. Unlike network planning and traffic engineering, network engineering problems are relevant at time scales ranging from hours to weeks. A these time scales, the dynamic evolution of the traffic load is an important factor that must be taken into account in the configuration of the network. Moreover, the periodicity of the traffic load evolution observed in operational transport networks suggest that the traffic may be modeled deterministically. We propose a dynamic deterministic traffic model called Scheduled Lightpath Demands (SLDs). An SLD is a connection demand represented by a tuple (s, d, n, alpha, omega) where s and d are the source and destination nodes of the demand, n is the number of requested connections and alpha, omega are the set-up and tear-down dates of the requested connections. The model captures the time and space distribution of a set of connection demands and, being deterministic,eases the use of combinatorial optimization techniques to solve network optimization problems. We investigate three network optimization problems involving the SLD traffic model: - We first study the Routing and Wavelength Assignment (RWA) for SLDs problem in a wavelength-switching network. The routing problem is formulated as a combinatorial optimization problem with two possible objective functions. We propose a Branch & Bound (B&B) and a Tabu Search (TS) algorithm that compute, respectively, exact and approximate solutions. Wavelength assignment is formulated as a graph coloring problem. We use an existing greedy algorithm to find approximate solutions. - We then investigate the problem of Diverse Routing and Spare Capacity Assignment (DRSCA) for SLDs in a wavelength-switching network. The problem consists of defining a pair of span-disjoint paths for each SLD so that the number of required working and spare channels is minimal. We propose a channel reuse technique to reduce the required working channels and a backup multiplexing technique to reduce the spare channels required for protection. The problem is formulated as a combinatorial optimization problem. We propose a Simulated Annealing (SA) meta-heuristic algorithm to compute approximate solutions. - Finally, we investigate the problem of Routing and grooming of SLDs (SRG) in a multi-granularity switching network. We consider a network whose nodes have a wavelength cross-connect (WXC) and a waveband cross-connect (BXC). The problem is formulated as a combinatorial optimization problem. We propose a parallel TS meta-heuristic algorithm to compute approximate solutions. We determine the conditions under which a network based on multi-granularity switches is more economical than a wavelength-switching (single-granularity) network.

Field demonstration of in-line all-optical wavelength conversion in a WDM dispersion managed 40-Gbit/s link

Abstract: The development of wavelength-division multiplexing (WDM) all-optical transport networks is an interesting solution to increase the capacity of long-haul transmission systems and to solve the route-exhaust problems of metropolitan networks, driving down the cost of that traffic. Routing can be achieved using a transparent device able to select and interchange wavelengths, such as an all-optical wavelength converter. In this paper, an optical transport network over an embedded link located between Rome and Pomezia in Italy is emulated. The transmission has been realized along a WDM, 5/spl times/100 km long, dispersion managed link at 40 Gb/s. The in-line rerouting process has been controlled by means of an all-optical wavelength converter realized with a periodically poled lithium niobate waveguide. Moreover, a polarization-independent scheme for the converter has been exploited to allow the in-line signal processing. This scheme is based on the counterpropagation of TE and TM signal components along the same guide and results extremely compact. In this paper it is demonstrated that wavelength conversion and rerouting add no penalty with respect to the simple transmission along the embedded cable. This result seems to be another step toward the feasibility of true all-optical networks.

Key elements of high-speed WDM terrestrial free-space optical communications systems

Abstract: This paper presents key operational elements which impact upon performance characteristics for terrestrial free-space laser communications systems within the 1550 nm window. These elements include; optical transmit and receive functionality of the telescope terminals, electro-optic components as well as atmospheric conditions affecting link performance.

Experimental evaluation of Extended OpenFlow deployment for high-performance optical networks

Abstract: Hybrid GMPLS-OpenFlow and novel Extended OpenFlow approaches are presented and experimentally evaluated on a converged packet and circuit switching setup. Extended OpenFlow agents, controllers and network application are developed & their performance evaluated on commercial ROADMs for the first time.