Duobinary technique for dispersion reduction in high capacity optical systems-modelling, experiment and field trial

The paper presents optical duobinary signalling as an alternative to the binary format for improved transmission performance in dispersion-limited systems and summarises results achieved from both experimental and theoretical investigations. The potential advantages of duobinary transmission for dispersion accommodation in high capacity systems are demonstrated in both laboratory experiments and installed optical fibres. Unrepeatered transmission at 10 Gbit/s without dispersion compensation was achieved with penalties of only 1.5 dB after 120 km and 2.5 dB after 138 km. Initial indications of the influence of self-phase modulation (SPM) and stimulated Brillouin scattering (SBS) on duobinary transmission are also presented. Two channel, 2×10 Gbit/s wavelength division multiplex (WDM) operation with mixed binary and duobinary transmission was demonstrated in a field trial. This is the world´s first demonstration of using both duobinary and binary signallings at a total capacity of 20 Gbit/s over installed fibre. The investigations show that duobinary signalling should become an important transmission format for future wideband networks where system performance is primarily dispersion dominated