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Superhighway by photonically and electronically enhanced digital transmission


The main objective of this project is to demonstrate the feasibility of very high bitrate (20 Gbit/s up to 40 Gbit/s) optical transmission systems in the transit network, using the electrical time division multiplexing (ETDM) approach.
The first achievements are:
Semiconductor circuit technologies suitable for 40 Gbit/s operation have been identified
Simulations for 40 Gbit/s circuits have been carried out using different technologies (SiGe, HEMT-GaAs, InP HBT, GaAs PHEMT)
Numerical system simulations demonstrate the feasibility of four-level DST at 20 Gbit/s over 140 km and at 40 Gbit/s over more than 40 km of standard single-mode fibre
System simulations on duobinary-DST and modified duobinary-DST have been carried out
Experimental characterisation of high speed laser diodes shows their suitability for 40 Gbit/s 4-level modulation
A 20 Gbit/s photo-receiver has been realised
A 20 Gbit/s field experiment over a 46.2 km installed standard single-mode fibre loop between Stuttgart and Ludwigsburg in Germany (using fibre cable rented from Deutsche Telekom) has been carried out successfully (BER< 10-9) using four-level Dispersion Supported Transmission.
A 40 Gbit/s 4-level DST feasibility field experiment yields an open eye-diagram

46.2 km installed standard single-mode fibre loop between Stuttgart and Ludwigsburg in Germany

Further project plans are:
Study and implementation of electronic processing functions
Design of high bitrate integrated circuits
Assembly of electronic sub-circuits and circuit boards
Realisation of high speed laser module
Realisation of high speed receiver
20-40 Gbit/s transmission on 120 km dispersion shifted fibre
20-40 Gbit/s transmission on 40 km standard single-mode fibre
Contributions to standardisation
Expected Impact
The results of the project are expected to be exploited in the standardisation, design and development of future 40 Gbit/s ETDM optical transmission systems for the backbone of the information superhighways of the future. The main application areas of these systems are expected to be transit lines for telecom applications in order to cope with increasing demand for high capacity lines due to the aggregation of traffic, feeder lines for provision of Internet and multimedia services enabling the interconnection of e.g. multimedia video servers to digital fibre-to-the-curb or fibre-to-the-home interactive systems, and high quality inter-studio links for transmission of several uncompressed digital HDTV or TV studio signals.

Main contributions to the programme objectives:
Main deliverables
Long distance, high speed single wavelength transmission at 40 GBit/s, using quaternary encoding, over standard in-field installed telecommunications optical-fibre, accomodating the PMD.
Contribution to the programme
Results will be exploited in future STM-256 40 Gb/s optical transmission systems.
Technical Approach
The optimum combination of advanced photonic and electronic processing technologies will be assessed with respect to techno-economic constraints. In order to realise optical transmission systems in a most simple and cost effective way, a single optical carrier from a single optical source in combination with the electrical time division multiplexing (ETDM) scheme will be used. Transmission on both dispersion-shifted and standard single-mode fibre will be studied with special emphasis on the reuse of existing fibre infrastructure. Thus, taking into account a typical repeater spacing of about 40 km used today, the goal of the project is to transmit up to 40 Gbit/s over at least 40 km (or multiples) of standard single-mode fibre.
It is expected, that fibre dispersion will be the most severe limiting effect. To cope with the fibre dispersion, advanced modulation formats, especially an upgrade of Dispersion Supported Transmission (DST) technology and the use of different multi-level modulation and detection formats will be studied in detail. Research will be carried out on system design (e.g. optical modulation format, electronic processing functions, advanced equalisation, assessment of system limitations) and supporting technologies (e.g. high-bitrate circuits, high speed optical sources). This work will result in a 20-40 Gbit/s experimental system testbed.
Summary of Trial
A 20 Gbit/s field experiment on standard single-mode fibre with STM-1 interfaces to application signals will be carried out. The fibre infrastructure in the Lisbon area of the project partner CPRM in Portugal (National Host) can be used. Before this, feasibility field experiments have been carried out at 20 Gbit/s and 40 Gbit/s over a 46.2 km installed standard single-mode fibre loop between Stuttgart and Ludwigsburg in Germany.
Key Issues
Identification of techniques for 40 Gbit/s ETDM optical transmission
Identification of 40 Gbit/s ETDM transmission limitations
Realisation of a 20-40 Gbit/s laboratory system testbed
20 Gbit/s field experiment, re-using existing fibre infrastructure
Identification of system application areas

Funding Scheme

CSC - Cost-sharing contracts


Alcatel SEL AG
Lorenzstrasse 10
70435 Stuttgart

Participants (5)

Companhia Portuguesa Radio Marconi
France Télécom
38-40 Rue Du Général Leclerc
92131 Issy-les-moulineaux
Avenida Rovisco Pais 1
Universitaetsstraaye 150
University of Aveiro