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Wavelength-agile optical transport and access network


The aim of WOTAN is to provide a managed, end-to-end wavelength-agile optical communications system for public telecommunications networks. Wavelength agility across a large number of closely spaced wavelengths increases the bandwidth capacity of the network, and enhances traffic management flexibility. WOTAN will investigate the optimum mix of optical and electronic solutions for switching and networking, across both access and core, to provide an integrated, managed network platform, that maximises the evolutionary potential of the network.

A major objective of the WOTAN project is to understand and demonstrate how core and access networks can be effectively integrated through the common use of WDM (wavelength-division-multiplexed) channels. A second aspect is the use of wavelength agility; thus for example different PONs (passive optical networks) may be connected simply through the choice of wavelength, using distributed switching and routeing techniques. Extension and evolution of such techniques may enable considerable reduction in the number of switches necessary in a network.
Understanding of how best to construct, control, manage and evolve towards a lean, yet future-proofed (ie scaleable), end-to-end broadband national network platform. Strategies for implementing WDM technology in a public telecommunications network.
Expected Impact
Flatter and leaner structures for a cost-effective broadband public telecommunications network, through:
Upgrade of broadband PON systems
Extensive WDM and wavelength agility
Seamless end-to-end connection of high capacity optical channels across access and core.
All-optical distributed switching of all customer connections (single tier)

The need for new wavelength standards for fine channel spacings (<100 GHz) is expected.

Potential WOTAN test-bed.

Main contributions to the programme objectives:
Main deliverables
An end-to-end wavelength agile optical communications system using WDM
Contribution to the programme
The technology for a scaleable end-to-end optical broadband network
Technical Approach
Four major networking concepts will be developed and demonstrated, employing wavelength agility and distributed wavelength routeing and switching, with increasing numbers of wavelength channels:
Upgrading broadband PON system by WDM
Head-end and switch-node by-pass for high capacity channels (end-to-end all-optical customer channels directly across access and core, eg for LAN-LAN interconnection)
Alternative core network structures (comparison of ring, star and mesh)
All-optical, end-to-end distributed switching (0.4 nm WDMA/TDMA)
Key elements of the project will include:
Tunable transmitters and receivers as wavelength-agile modules
Wide bandwidth, wavelength-flattened and gain-clamped Yb/Er optical amplifiers
Grating-based NxN wavelength multiplexers (passive wavelength-routeing node - PWRN)
Variable waveguide attenuator arrays
All-optical wavelength converters
Broadband PON system
Optical cross-connects (3 input and output fibres, 1.6 nm, 16-channel capability)
Wavelength referencing sub-systems
Commercial SDH and ATM equipment/layers
Integrated network management platform
End-to-end networking trial
Sub-systems in the WOTAN network will be element-managed by the network management system.
Summary of Trial
Through the BBC's sponsorship of WOTAN and interaction with internal BT projects, it has been possible to demonstrate an end-to-end high capacity application across BT's London-East Anglian Network (LEANet). This is an advanced, multi-layer transport network test-bed, interconnecting a number of towns and cities in the UK. The demonstration used BBC HDTV equipment and codecs to transmit compressed HDTV and conventional 625 line PAL signals at 270 Mb/s across LEANet into BT Laboratories' VisionDome (supplied by ARC, Raleigh, USA). The VisionDome provides a 180° visual and audio environment for interworking of computer generated and real environments, eg for immersive multimedia environments, video conferencing and shared work spaces.

The WOTAN project will culminate in an integrated, end-to-end networking trial, carrying representative customer traffic and services from the "Futures Test-Bed" National Host at BT Laboratories, over LEANet. By making use of the resources of this test-bed and the advanced hardware developed within WOTAN and other ACTS projects (specifically including BLISS), the fibres will be configured as required (subject to operational availability) to demonstrate and test the proposed end-to-end networking principles, sub-systems and technologies. In addition, it is the intention to undertake a joint demonstration of LAN-LAN services and applications with COBNET.
Laboratory Demonstrator
A laboratory demonstration of an all-optically switched network will also be undertaken. An all-optical, distributed switching sub-system, employing time- and wavelength-agility (WDMA/TDMA) with 0.4 nm channel spacing, will demonstrate the future-proofing capability of optics, to provide very high switched network throughput between customers or terminals on different PONs, without the need for electrical (ATM) switches; a "switchless" network. Elements of the demonstrator will show the potential to operate over a national scale, with closer channel spacings.
Key Issues
The end-to-end nature of the WOTAN project will address:
continuous and long-term scalability with traffic demand
impact of customer bandwidth demands and applications on core and access network design and operation
cost-effective (lean) network structures and technologies
interworking issues at the access and core network interface
the role for an all-optical end-to-end link across the access and core networks
the role for all-optical distributed switching
wavelength channel numbers and spacings
advanced network, traffic and element management
issues of managing wavelength-agile PON access networks and wavelength-routed core networks within a unified networking environment
interworking of management platforms for the optical access, optical core and electrical (ATM/SDH) network fabric
evolution plans and roll-out strategies
contributions to the international standards debate in the area of wavelength standardisation

Funding Scheme

CSC - Cost-sharing contracts


Sopers Lane
BH17 7EQ Poole
United Kingdom

Participants (9)

United Kingdom
Centro Studi e Laboratori Telecomunicazioni SpA
Via G. Reiss Romoli, 274
10148 Torino
United Kingdom
ISA-Jobin Yvon
Italtel Società Italiana Telecomunicazioni SpA
Castelletto Di Settimo Milanese
20019 Milano
Sirti SpA
Via G.b. Pirelli, 20
20124 Milano
University of Cambridge
United Kingdom
Trumpington Street
CB2 1PZ Cambridge
University of Essex
United Kingdom
Wivenhoe Park
CO4 3SQ Colchester