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.

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.

This paper presents a global methodology and optimization options for dimensioning the WDM optical layer in future transport networks. Several optimization processes are discussed and compared with results on the same study case, the European Optical Network. In particular, the results show the significant benefits of wavelength conversion and the advantages of "least number of hops" path routing among the various path routing strategies for wavelength channels. The connection rerouting optimization process, which requires a more algorithmic approach, is described along with the different criteria used to choose the optimized parameters (load on the link, fiber utilization ratio, etc.). The results on the European Optical Network case study illustrate that a global point of view should be adopted when optimizing these parameters as some processes can lead to worse dimensioning results.

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.

Future optical networks will be operated with wavelength division multiplexing (WDM). Three different routing strategies for optical paths are presented here to perform allocation of resources (wavelengths) in WDM optical networks. Resource allocation has been studied with two different approaches, based respectively on wavelength routing and wavelength translation schemes. The implications of these routing strategies on WDM network dimensioning are explained and the results are illustrated on a European Optical Network test-case showing a major reduction of the number of needed fibres and pointing out the interest of wavelength translation.

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 project's 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.

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.>