Francesco Masetti

Optical routing of asynchronous, variable length packets

We discuss the introduction/implementation of optical IP routers, then we introduce a novel scheduling algorithm incorporating void filling and aimed at optical routing of asynchronous, variable packet length packets. We describe its structure and discuss the complexity issues. Albeit introduced with the purpose of cancelling expensive optical synchronization, we argue that this approach represents the most viable all-optical approach for implementing packets-over-SONET (IP-centric scenario). We also present simulations under self-similar traffic conditions which point to the inefficiency of optical buffering to combat the effects of self-similarity, and we outline alternative strategies for proper buffer dimensioning.

High speed, high capacity ATM optical switches for future telecommunication transport networks

This paper describes the work carried out in the RACE Project R2039 ATMOS (asynchronous transfer mode optical switching). The project is briefly illustrated, together with its main goal: to develop and assess concepts and technology suitable for optical fast packet switching. The projects technical approach consisted in the exploitation of the space and wavelength domains for fast routing and buffering: The major achievements are then reported. Four different switch architecture concepts have been proposed, investigated and developed, all based on a high speed optical routing matrix electrically controlled at lower speed. The basic optical key components and subsystems (wavelength converters, space switches and optical buffers) are described in detail, with the outstanding results obtained and the corresponding projected performance. In particular, system demonstration of wavelength conversion at 10 and 20 Gb/s has been realized, to show the usefulness of the ATMOS technology both to implement optimized high performance optical packet-switching fabrics as well as transparent optical circuit-routing nodes. Four rack-mounted, reduced size demonstrators of basic switching matrices have been designed and implemented scalable to real system sizes. The obtained good results in terms of bit error rate and hardware integration are reported, showing that ATM switches are feasible with state of-the-art optical technology.

Design and implementation of a fully reconfigurable all-optical crossconnect for high capacity multiwavelength transport networks

The motivations and application framework for the introduction of all-optical wavelength division multiplexing (WDM) transmission and routing techniques in the transport network are presented. The requirements and functionalities of all-optical transparent routing nodes are discussed, and the physical architecture of a crossconnection node is proposed, to meet these requirements. Optical devices suitable for the node implementation are compared, and first demonstrations of crossconnection function at data rates up to 10 Gb/s are given. These results bring experimental evidence of the high potential of all-optical routing nodes for actual implementation of multiwavelength transport networks.

Survivable networks based on optimal routing and WDM self-healing rings

The design of survivable all-optical networks based on self-healing WDM rings (SHR/WDM) to provide 100% protection from any single link failure requires the joint solution of three sub-problems. These are the ring cover of the mesh topology (the RC sub-problem), the routing of working lightpaths between node pairs to support traffic demands (the WL sub-problem) and the selection of the SHR/WDM spare wavelengths for the protection of every link traffic (the SW subproblem). This paper presents an integer linear programming (ILP) formulation of the problem of minimizing the total wavelength mileage (/spl lambda/-miles) required to support a set of given traffic demands in a given network topology using SHR/WDM employing 1:N line protection mechanism (the WRL problem). This formulation allows to jointly and optimally solve the three subproblems, and yields up to 15% reduction of the total /spl lambda/-miles required by existing solutions that separately resolve the sub-problems. A simplified sub-optimal solution of the WRL problem is also provided, that yields results few percent worse than the optimal solution and that is tractable for networks whose size is on the order of the pan-European network, i.e., 19 nodes.

Fiber delay lines optical buffer for ATM photonic switching applications

An optical buffer shift register based on a set of fiber delay lines is presented, with the goal of providing cell storage and queuing in asynchronous transfer mode (ATM) photonic switches. The concept of multiwavelength cell buffering is adopted, to realize a shared buffer with a storage capacity equivalent to a set of shift registers. Since only one wavelength-encoded cell must enter one delay line at each time slot, contention resolution is necessary to determine the queuing order between the incoming cells. The use of optical fibers as delay lines and semiconductor optical amplifiers as gates associated with passive splitters to realize buffering and time-switching has been demonstrated. An experimental setup has been implemented at 600 Mb/s and operates without guard bands between packets. The low penalty observed shows that system synchronization and reliability are good.<<ETX>>

Design and implementation of a multi-terabit optical burst/packet router prototype

This paper reports the first demonstration of a multi-terabit IP optical router. A sub-equipped rack-mounted prototype has been designed and assembled, demonstrating all key functions of large, scalable packet router. The design exploits burst switching techniques through to an integrated optical packet switching fabric.

Key building blocks for high-capacity WDM photonic transport networks

The objective of this paper is to give an overview of the different studies we have performed at the research level regarding the design and implementation of a photonic wavelength division multiplexing (WDM) layer providing transparent transport services to client layers (SONET/SDH, ATM, etc.). Such a network requires a number of enabling factors to be assessed in order to become a reality. Among these factors are the availability of high-capacity WDM transmission systems and efficient optical routing nodes based on mature technology, the design of robust networks optimizing the utilization of resources, and the development of a management system in accordance with presently applied standards for transport networks. We review our achievements in these different fields.

System Functionalities and Architectures in Photonic Packet Switching

An overview of characteristics and challenges of photonic packet switching is given, illustrating its potential advantages within future nodes and networks, then describing basic system functionalities (photonic routing, optical buffering, photonic processing) and finally illustrating, as possible examples, combinations of essential building blocks within the architectures developed in the frame of the RACE project ATMOS and of the ACTS project KEOPS.

Dimensioning and design of the WDM optical layer in transport networks

Wavelength-division-multiplexing (WDM) techniques are now widely spread for high bit rate transmission. Beside the increase of the transmission capacity, WDM should be used in flexible, transparent and cost effective solution for routing large amount of traffic in the optical domain. WDM networking implies a novel network analysis in order to define the traffic transported and routed optically, the protection/restoration schemes more adapted to the optical domain and the reconfiguration possibilities. The WDM optical layer dimensioning is presented here and shows the design and optimization of this transport layer in terms of transmission resources (wavelengths, fibers, amplifiers) and optical node functionalities (optical add-drop multiplexers, optical cross- connect, wavelength translation, . . .). A dimensioning methodology is established, defining the main inputs of this task and the main issues. In this paper different options and issues of the WDM dimensioning are presented and discussed. First, the optical path routing is studied and different routing strategies are given for the minimization of specific parameters. The second issue concerns pure resource allocation. Two different approaches based respectively on wavelength routing and wavelength translation are introduced. The benefits of wavelength translation is discussed and different criteria for the location of this functionality are established. The discussion and analysis are illustrated on several test cases covering different network topology assumptions.

Design, modelling and implementation of the ATMOS project fibre delay line photonic switching matrix

This paper presents the fibre delay line switching matrix, a high-performance photonic system consisting of an electrically controlled optical high-speed transport network. This photonic matrix adopts the asynchronous transfer mode (ATM) technique and an internal self-routing architecture based on wavelength encoding, for cell routing and multiplexing. A set of output queues provides the buffering function.An extensive performance evaluation is presented, with reference to both the traffic throughput and technology feasibility. Numerical results have been obtained to evaluate optical performance and the implementation of a 4×4 demonstrator, supporting a 2.5 Gbit s-1 input/output rate, shows the feasibility of the matrix with state-of-the-art optical technology.Its high performance makes the fibre delay line switching matrix a strong candidate for implementing the core of future high-speed broadband ATM switches.