E. Van Breusegem

An optical IM/FSK coding technique for the implementation of a label-controlled arrayed waveguide packet router

In this paper, we present a new concept of optical packet/burst switching suitable for generalized multiprotocol label switched (GMPLS)-based optical networks. In such networks, optical labeled switched paths are being established in a similar way as label-switched paths in MPLS. We use a wavelength label as well as an orthogonally modulated label, with respect to the payload modulation format, and which is encoded using either frequency-shift keying (FSK) or differential phase-shift keying (DPSK). Wavelength is used for switching in the node, whereas the orthogonal label defines the label-switched path. We present both simulation and experimental results to assess transmission performance of the proposed combined modulation scheme. In addition, we propose a suitable optical node architecture that can take advantage of this stacked label concept. Toward this, we use widely tunable wavelength converters to efficiently route IM/FSK (or IM/DPSK) optically labeled packets in an arrayed-waveguide grating (AWG)-based node structure. We present performance simulation results in terms of packet loss ratio and internal block probability. Internal blocking is an inherent problem of AWG optical routers, and a specific wavelength assignment algorithm has been developed to minimize it. Finally, the feasibility of IM/FSK transmission is experimentally demonstrated over an 88-km single-mode fiber span, and novel aspects of FSK generation and detection techniques are presented.

Clos lives on in optical packet switching

While the technological evolution since C. Closs seminal article (see Bell Sys. Tech. J., vol.32, p.406-24, 1953) on multistage switch architectures has been huge, his work and ideas still live on. We discuss node architectures for optical packet switching and show how the multistage approach proposed by Clos can be adopted to solve scalability issues and construct switches with large port counts. As in the old days, the driving factors behind the introduction of multistage concepts also include economic issues: compared to a single-stage architecture, the number of components to realize the switching fabric is reduced.

Performance improvement of an internally blocking optical packet/burst switch

Optical packet/burst switching is considered a promising technique to improve the performance of optical networks. Key components in these technologies are the optical switching nodes. Some of these node architectures suffer from internal blocking. Synchronous operation allows overcoming most of the problems introduced by this internal blocking. However, in asynchronous networks internal blocking can have a more pronounced effect. In this paper, we propose a windowing technique to improve the performance of internally blocking optical switching nodes in asynchronous operation. Simulations will show significant improvements can be made.

Label-Controlled Optical Packet Routing—Technologies and Applications

An overview is given of various optical packet labeling techniques. The architecture and technologies are discussed for optical packet routing nodes using orthogonal labeling with opto-electronic label processing, and for nodes using time-serial labeling with all-optical time-serial label processing. An example of a near-term application is given, and a comparison of routing technologies is made regarding their cost and reliability aspects.

ORION: a novel hybrid network concept: overspill routing in optical networks

As more and more packets needs to be handled in the network, wavelength switched optical networks reduce the number of packets that need to be handled. However, this results in inefficient wavelength usage. Furthermore, it can only cope with traffic variations on a larger time scale. On the other hand, optical packet/burst switching (OPS/OBS) can cope better with traffic variations, but there is the contention resolution problem and the large number of handled packets. Is it really necessary to make this choice between black and white, or is it possible for these two to meet in the (gray) middle? We propose a novel networking architecture, trying to find a working marriage between these two - overspill routing in optical networks (ORION) - a network that is basically wavelength switched, but traffic can spill over in a packet switched modus, which allows a way to cope better with variable traffic profiles.

Controlling LSPs in an ORION network

New networking paradigms try to combine packet switching and circuit switching, keeping the best of both worlds and getting rid of the drawbacks. One promising technology is overspill routing in optical networks (ORION). In this paper we develop a control technique to set up LSPs in this novel network environment. It is based on the GMPLS paradigm and needs no extra control messages.

Optical label switched networks: laboratory trial and network emulator in the IST-STOLAS project

This article reviews the performance of an optical-label-controlled packet routing node as implemented in the European FP5-IST STOLAS project including a set of general engineering rules. Experimental networking scenarios and results from a STOLAS based network emulator supporting optical overspill routing are presented

GMPLS extensions for supporting advanced optical networking technologies

In response to the need for higher flexibility in optical networks, a generalised multiprotocol label switching (GMPLS) protocol suite is currently under standardisation. However, in these standards a label switched path (LSP) hierarchy is defined that only considers circuit-switched optical networks. The paper aims at broadening the scope of this hierarchy to more advanced optical networking technologies.

Upgrade scenarios for OPS networks

Optical Packet Switching can cope well with the bursty nature of data traffic that is becoming predominant. OPS nodes will be used in a network, where traffic demand will show a growth evolution. In stead of immediately installing a large OPS node that is only sparsely used in the first years, we prefer solutions allowing the switch to grow as traffic demand grows. We look into modular, multi-stage solutions for two well-known OPS node designs. We evaluate the cost evolution for different design choices, using several scenarios. We show that multistage OPS node designs can result in cheaper, modular upgradeable designs.

Cost efficient upgrading of OPS nodes

We come back on a technique to build modular switch nodes. This approach allows for a more cost effective expansion of OPS nodes. We give two example designs, showing that the method is useful only for Broadcast & Select OPS nodes when taking price decrease in function of time into account.