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Keys to optical packet switching


The main objective of the KEOPS project is to define, develop and assess the concept of optical packet switching and routing networks capable of providing transparency to the payload bit rate, using optical packets of fixed duration with low bit rate headers, to simplify processing at the network/node interfaces. The feasibility of the KEOPS system concepts will be assessed by modelling, laboratory experiments, and testbed implementation of optical packet switch nodes, a network/node interfacing block and a fully equipped demonstrator.

Network reference structure
Demonstration of benefits of transparent optical packet layer within an all-optical network reference structure:
* First conclusive results showing high transmission efficiency and traffic smoothing by an ATM/Optical Transparent Packet Interworking Unit with optical packet format defined in KEOPS;
* Assessment of switching node performance and synchronisation schemes;
* Exploitation of wavelength domain in network and switch node;
* World state of the art performance of photonic devices and modules, successfully tested in KEOPS and OPEN trials;
* Regenerative and bit rate transparent monolithically integrated interferometric all-optical wavelength converters (up to 40 GHz);
* Fast optical gates operating over the whole EDFA range (16 channels at 10 Gb/s) using clamped gain SOAs;
* Low insertion loss (6 dB), high speed electro-optic space switches;
* Basic principles of the switch blocks explored up to 20 Gb/s and partial operation of interfacing block architectures (coarse and fine synchronizer) demonstrated;
* Wavelength Routing Switch demonstrator now sufficiently equipped to demonstrate 4x4 wavelength-based packet routing at 2.5 Gb/s and 622 Mb/s real-time header recovery;
* Demonstration of 160 Gb/s throughput with a sub-equipped 16x16 Broadcast-and-Select switch testbed. Cascadability of 8 network sections (50 km of DSF + 16x16 switch + regenerative interface) demonstrated at 2.5 Gb/s with low sensitivity penalty.
Expected Impact
By developing new key components for photonic switching, validating system concepts, and proposing new network concepts adapted to the customer needs (transparency to the bit rate), the KEOPS project will provide the fundamental basis for the introduction of packet switching techniques in the future transparent optical IBC network.

Main contributions to the programme objectives:
Main deliverables
Optical packet-switching in an all optical network.
Contribution to the programme
Development of a key basic technology for the future all-optical IBC network.
Technical Approach
The work is organized in three workpackage groups:
* "Networks and Systems" undertakes studies on the network reference model, traffic analysis and switch node design, including modelling and specifications;
* "Functional Sub-Blocks" provides advanced optoelectronic devices and modules required for system testbed implementation;
* "System Demonstration" includes assessment of switching and interfacing blocks and demonstration of a transparent optical packet switch node.

The system concepts employ switch architectures using photonic techniques (space and wavelength switching for routing and multiplexing, time switching using optical fibre buffers), to perform packet routing, multiplexing and buffering. Use of electronics is reserved for the switch control, where speed is not a limiting factor. The concepts are validated in experimental testbeds built from state-of-the-art photonic technology.
Summary of Trial
A demonstrator and testbeds will be implemented in a laboratory:
* to assess the switching and interfacing blocks including packet synchronization (delineation and phase alignment);
* to demonstrate and assess switching node architectures which provide for transparency to the payload bit rate, multicasting and cascadability.

In addition, components from KEOPS will be used in the field trials of the ACTS OPEN project.
Key Issues
* definition and analysis of an optical network layered structure to handle high bit rate bursty traffic and to bridge the granularity gap, between the electrically switched capacity blocks and the transparent wavelength channels in the core network;
* definition of the best packet format for transparent optical packets, using fixed packet load duration whatever the user defined load bit rate (e.g. 155 Mb/s to 10 Gb/s), and packet headers with a fixed and lower bit rate (155 or 622 Mb/s) to allow electronic processing;
* traffic analysis and throughput performance evaluation at both the network and node levels;
* specification of switch node architectures allowing for multicasting, cascadability, interoperability of the different architectures, and the design of network/node interfaces;
* development of key components for use in both Optical Packet Switching and Optical Transport Networks;
* fabrication of required advanced functional modules to experimentally demonstrate the KEOPS system concepts, based on fast optical routing in the wavelength/space domains and optical packet buffering for contention resolution;
* delivery of components to the OPEN project for implementation in their field trials;
* implementation of testbeds and a demonstrator operating at bit rates of 2.5 and 10 Gbit/s.

Architecture of the Wavelength Routing Switch Demonstrator

Funding Scheme

CSC - Cost-sharing contracts


Alcatel Alsthom Recherche
Route De Nozay
91460 Marcoussis

Participants (8)

Lorenzstrasse 10
70435 Stuttgart
Alcatel CIT SA
Centro Studi e Laboratori Telecomunicazioni SpA (CSELT)
Via Guglielmo Reiss Romoli 274
10148 Torino
Raemistrasse 101
France Télécom
38-40 Rue Du Général Leclerc
92131 Issy-les-moulineaux
Via Zamboni 33
40126 Bologna
United Kingdom

G1 1XQ Glasgow