10 Gbit/s, 138 km uncompensated duobinary transmission over installed standard fibre

The first field demonstration using optical duobinary signalling at 10 Gbit/s over installed fibres is reported. Transmission over 138 km of standard fibre is demonstrated without repeaters or dispersion compensation and with a penalty of only 2.5 dB. This technique significantly increases the bit rate distance product without changing any specifications of the existing fibre network. The influence of fibre nonlinearity on system performance is also investigated. >