PHOTON shall bring the available photonic technology to the field and tackle the challenge of a photonic network. It aims at the following objectives:
To develop selected conception items for the future pan-European transport network with focus on an all optical network.
To implement key functionalities and components by a field demonstrator network based on installed standard single mode fibres.
To demonstrate all optical wavelength division multiplex (WDM) transmission with data rates up to 10 Gbit/s per wavelength over 500 km.
Furthermore, to demonstrate WDM cross connecting, optical WDM supervision and application of the WDM transport network.
The project has entered its implementation phase. In the past the focus has been on design, implementation of modules, fabrication of components, and first experiments.
The study of optical networks, in principle and by simulation, yielded feedback for the design of the field trial and a solid basis of knowledge for the future optical network.
Design rules for the WDM link and the optical cross connect (OXC) lead to a future-proof modular design for the field trial, where each section of the link deals with its own loss, dispersion and non-linear effects independently of preceding and subsequent link sections. A first verification of the link design in the laboratory has demonstrated error free transmission of a 10 Gbit/s signal over 500 km of standard fibre.
The OXC has been designed in a way that it could be placed at any amplifier site along a WDM line. Losses are compensated within the OXC and the channels for each WDM port are equalised. For the field trial only passive equalisation is possible within the scope of the project. But the necessity has been identified to employ - in future all-optical networks - optical amplifiers for each single channel within the OXC. For further photonic research it is recommended to work on cost-effective, gain-controlled optical amplifiers with adjustable output power.
For use in PHOTONET first samples of 10 and 2.5 Gbit/s transmitter modules according to the specification and eight WDM filters have been delivered. The WDM filters were improved in crosstalk suppression compared to the previous report.
PHOTON will show the way to cost effective, high bit rate signal transfer and flexible allocation of huge network resources which are necessary for the information highways of the future. It will achieve an important first step to the future optical transport network in the core area of the European integrated broadband communications network.
Main contributions to the programme objectives:
Key technologies for a pan-European WDM photonic transport network
Contribution to the programme
Establishes technologies for a future cost-effective high bitrate WDM broadband network
The project has four main parts
The first part deals with network issues, WDM link evaluation, and network operation. Work in this field is supported by link and network simulations. Network operation under field conditions will be conducted using a demonstrator star network. A WDM network node (optical cross connect - OXC) will be linked by WDM transmission lines between three cities in two European countries. To provide interfaces to the existing core network SDH equipment for 2.5 and 10 Gbit/s will be supplied and adapted to the requirements of WDM.
The second part covers the area of long-haul, high bit rate optical transmission for WDM transport. Transmission uses optical non return to zero (NRZ) signals in the 1550 nm window where special attention is given to the use of the already installed SSMF infrastructure. Dispersion and attenuation is compensated for by implementing dispersion compensation modules and Erbium-doped fibre amplifiers (EDFAs) for long-haul transmission (up to 500 km) without electrical regenerators.
The WDM OXC is being implemented in part three. Its realisation follows a modular approach in order to pave the way for future node enhancements. An optical overhead channel is terminated and processed within the cross connect to provide the basis for WDM supervision.
In the fourth part key components for high-speed transmitters, WDM optical filtering and optical wavelength referencing in network nodes are being realised.
Summary of Trial
The field trial consists of the realisation and application of a border crossing star network called PHOTONET, using WDM links and a WDM OXC. The WDM scheme of the field trial allocates 8 channels in the 1550 nm range. A 400 GHz spacing of the WDM grid is used in the German part of the network, whereas a 200 GHz spacing is used in the Austrian part. The field trial network is located between Munich and Vienna with the OXC in Passau.
PHOTONET is based on installed standard single mode fibres and, to the greatest possible extent, on commercially available components. It will demonstrate WDM transmission with data rates up to 10 Gbit/s per wavelength over 500 km, WDM amplification and dispersion compensation. Furthermore, it will demonstrate WDM cross connecting, optical WDM supervision and application of the WDM transport network.
A demonstration of data transfer under field conditions using not only randomly generated bit patterns will be done by means of SDH accesses. In particular newly developed 10 Gbit/s SDH terminal multiplexers will be supplied together with existing 2.5 Gbit/s SDH equipment. These SDH interfaces, modified to be WDM compatible, allow connections to the existing public core network and thus make it possible to carry out applications on the PHOTONET network and to establish connections to the "National Host" infrastructure. In addition a leased wavelength service will be supported. The field trial will be ready in mid 1998 and last at least three months.
To help create a network of the future the consortium has a broad basis of partners. One network user, four network operators, four industrial and two research partners are working on:
A conceptional basis for the core network (the pan-European "PHOtonic Transport Overlay Network" -PHOTON) with optical cross-connecting and optical transmission for the transfer of signals with data rates beyond 10 Gbit/s.
Demonstration of all-optical WDM transmission over 500 km, of optical cross connecting and of suitable network applications in a field trial set-up.
Functional specifications of WDM links, OXCs, WDM supervision, interfaces for the new optical transport network and interfaces to existing networks.
Verification and analysis by applying link evaluation methods.
Contribution to national/international standardisation bodies and other fora.