Christina Tanya Politi

Future Optical Networks

The summary form only given. Communication networks are undergoing dramatic changes due to increasing demands from a diversity of users. Consumers, scientists, business users all have there own specific requirements on the network in terms of bandwidth, quality of service, network resources (storage and processing). Optical technology has a key role to play in enabling networks that can support these demands, and this tutorial looks at how optics will increasingly penetrate the network. The tutorial will review the current status of networking, the role of optics in future networks (including current roadmap visions of the switching technologies to be used), major recent programmes [on optical networking] in regions of the world such as USA, Japan and EU are described.

OPSnet: design and demonstration of an asynchronous high-speed optical packet switch

This paper presents the results of the optical packet switched network (OPSnet) project, which investigated the design of an asynchronous optical packet switch suitable for the core of an optical transport network (OTN). The requirements for the switch were to control and route variable-length packets transmitted at bit rates beyond 100 Gbit/s. The subsystems and techniques used are analyzed and presented. Fast header encoding and passive decoding is based on the differential phase-shift keying (DPSK) method. The dual-pump four-wave mixing (d-p FWM) wavelength-conversion technique, in combination with an arrayed waveguide grating (AWG), is utilized for packet switching. An advanced and fully controllable mechanism for the packet-switch control is presented, which is implemented on field programmable gate array (FPGA) technology. The control wavelength is generated using a tunable laser, the actual wavelength and new header values are provided utilizing fast header recognition and look-up tables. The integration of the subsystems is discussed, and the results of a four-output port asynchronous packet-switch demonstrator operating at 40 Gbit/s are presented. Finally, the switch limitations are examined and design issues are discussed.

Dynamic behavior of wavelength converters based on FWM in SOAs

As wavelength converters based on four-wave mixing (FWM) in semiconductor optical amplifiers (SOAs) attract more attention, dynamic effects and wavelength dependent performance become key aspects to be investigated. Such issues are particularly important, as complex configurations are likely to be used to overcome challenges like tunability and polarization dependence. In this paper a numerical model is used to predict the dynamic performance of three FWM configurations and an analytical model is used to derive design rules. First, the wavelength dependent behavior of a wavelength converter is investigated and the requirement for a widely tunable converter is identified. Secondly, a configuration for extinction ratio (ER) improvement is studied and novel design rules are obtained analytically, tested experimentally and explained by the numerical model; experimental results with ER improvement at 10 Gb/s were achieved for the first time. The third configuration studied is a dual-pump arrangement enabling wide tunability. Fixed input/tunable output and tunable input/fixed output configurations are discussed in terms of optical signal-to-noise ratio and tunability. Design rules are extracted and verified for all three configurations that are likely to be deployed: simple wavelength converters, regenerating converters and tunable wavelength converters.

Optical packet routers: how they can efficiently and cost-effectively scale to petabits per second

Todays data-centric networks are becoming progressively dynamic with respect to the transported traffic volume, to the spatial and temporal variations of traffic patterns, and to the subsequent interconnection request patterns. Optical packet routers (OPRs) aim to provide a viable answer to these requirements by rendering the optical layer adaptable, reconfigurable at will, and cost-effective by means of statistical multiplexing of the network resources while satisfying end-to-end quality-of-service requirements. We study the role of OPRs in two different network approaches: an OPR adopting the legacy of a telecommunication solution and a solution pertinent to the role and the functionality of an IP world. To benchmark the two scenarios, a multilayer, multigranular OPR architecture is presented and its potential to cost-effectively scale toward petabit-per-second throughput is justified by means of physical layer performance and power consumption estimations for each case. Furthermore, the blocking and frame-loss performance of the proposed OPRs is presented, proving the viability of the proposed solutions.

Fast and widely tunable optical packet switching scheme based on tunable laser and dual-pump four-wave mixing

An optical packet switching scheme based on a fast electronically controllable tunable laser dual-pump four-wave mixing for wavelength conversion and an N/spl times/N arrayed waveguide grating for passive routing is examined. This scheme can realize ultrafast packet switching and large port switch fabrication, required in next-generation core optical packet routers. The performance is examined in terms of packet-based bit-error-rate measurements for packet-by-packet switching. Design issues are also discussed.

Integrated design and operation of a transparent optical network: a systematic approach to include physical layer awareness and cost function [Topics in Optical Communications]

The manner and exact timing of the evolution of the widely used DWDM infrastructure to a transparent optical network is judged on economic circumstances and network performance. In this context this article elaborates on a methodology developed within the Project 1ST NOBEL, for integrating cost functions and other design constraints into the planning of a DWDM network while considering this evolution perspective to a transparent optical network. This systematic approach builds upon the experience of static network design and is substantiated by specific examples in this article

Cross Layer Routing in Transparent Optical Networks

New algorithmically simplified WRA that incorporate physical layer criteria in the path establishment procedure are suggested and applied in the Deutsche-Telecom network. Their blocking performance superiority and physical performance guarantee are discussed.

Optical Wavelength and Waveband Converters

Wavelength conversion has been acknowledged as one of the most significant optical processing functions and various papers have been involved with investigating methods of translating very high bit-rate data into other wavelengths. This paper will give an overview of the recent advances in the area, with emphasis on methods that can be used as both wavelength and waveband converters, which can be used at higher bit rates without any configuration changes and are integratable and hence compact solutions. Four-wave mixing in SOAs is one of these techniques and we will elaborate on particulars of this technique. Switch architectures that benefit from wavelength and waveband conversion are presented

Routing in dynamic future flexi-grid optical networks

Routing in dynamic future optical networks will depend on the underlying technology and more specifically on whether standard grid or flexi-grid technology will be used. In particular for dynamic flexi-grid networks resource allocation and routing concerns both path establishment and allocation of specific spectrum which in turn relates to the modulation format of the transmitted signals. Moreover if variable bandwidth transponders are utilized simultaneous optimization of allocated spectrum and transponder reach should be performed. In this paper we investigate the benefits of flexi-grid technology with variable bandwidth transponders regarding blocking performance and spectral efficiency when compared to the standard-grid counterpart.

Hybrid burst/packet switching architectures from IP NOBEL

In spite of its long term promise, all-optical switching is still plagued by high cost, low efficiency when handling bursty data traffic, immature management and protection and poor output port contention resolution leading to heavy loss. Given the current situation, hybrid approaches that keep the best features of optics, reverting to the electrical plane when expedient, constitute sensible interim steps that can offer cost-effective solutions along the road to an eventual all-optical core. Two such approaches developed in the framework of the European IP project NOBEL are presented in this work. The first is a quite mature solution that extends present day concepts to achieve multiplexing gain while keeping all the management and restoration benefits of SDH. The other mimics early LANs in executing a distributed switching via its electrical control plane using two-way reservations, thus restricting its applicability to smaller domains. Combining the two leads to a system fulfilling most of todays requirements for Tb/s core networks.