- To demonstrate the feasibility of very high bitrate (up to 20 Gbit/s) optical transmission systems in the core network.
- To acquire the basic physical and technical knowledge necessary for system design at such bit rates.
The main objectives of the research are:
to demonstrate the feasibility of very high bit rate (up to 20 gigabits per second) optical transmission systems in the transit network;
to acquire the basic physical and technical knowledge necessary for system design at such bit rates.
The research involves:
practical experimentation to determine limits concerning bit rate and transmission span, aiming at a bit rate of 20 gigabits per second using optical and electrical time division multiplexing and demultiplexing and direct detection schemes;
theoretical studies and transmission system feasibility experiments at data rates above 10 gigabits per second over dispersive optical fibres, especially standard single mode fibres at 1.5 um laser wavelength;
the development and adaptation of electronic circuits and optical amplifiers for use in transmission systems.
Nonlinear pulse pattern propagation has been studied using numerical simulations in order to investigate 10 gigabits per second transmission in the 1550 nm window via standard single mode fibre (SMF).
Analytical calculations and numerical system simulations have yielded the dispersion limitations for several transmission schemes using linear propagation. System experiments at 10 gigabits per second via SMF in the 1550 nm window have yielded the dispersion limits for the direct intensity modulation and the external modulation approach. A new transmission method has been evaluated and a corresponding increase in the maximum repeaterless transmission span at 10 gigabits per second has been demonstrated to a record 151 km.
This work is related to a previous RACE project R1051. In a laboratory testbed, the physical and technological limits concerning bitrate and link length will be explored using direct detection schemes and time division multiplexing techniques. A bitrate approaching 20 Gbit/s is envisaged for the demonstrator, to be assembled at the location of the co-ordinating partner towards the end of the project.
Amongst the main challenges foreseen are the generation and detection of high speed optical signals (>10 Gbit/s) and transmission via dispersive fibres. Various techniques to overcome the dispersion problem will be studied. Emphasis is placed on investigating the new method of dispersion supported transmission (DST). This allows high bitrate transmission over dispersive fibres using a directly modulated laser diode. To perform these experiments, it is necessary to determine how optical amplifiers can be characterised and adapted to system needs. Requirements for special components (e.g. semiconductor lasers) will be met from other RACE projects where possible. In addition to the consensus management process, liaison links have been established with projects R2006 (WELCOME) and R2015 (ARTEMIS).
- Practical determination of limits concerning bitrate and transmission span, when using TDM and direct detection.
- Theoretical studies and system feasibility experiments at 10 Gbit/s and above over dispersive optical fibres, especially standard single-mode fibres at 1.5 um laser wavelength.
- Development and adaptation of electronic circuits and optical amplifiers for use in the transmission systems.
- Field experiment with the DST method.
TRAVEL's results are expected to have a major impact on the design of future STM-64 optical systems through contributions to standardisation bodies (ITU-T and ETSI).
The main application areas will be high quality inter-studio links for transmission of uncompressed HDTV, feeder lines for the provision of high quality signals for fibre to the curb or fibre to the home (HD)TV distribution systems, and transit lines for telecom applications in the trunk network and for interface with submarine systems.