Faster Communications on Existing Infrastructure

The 10-Gigabit Ethernet standard is encouraging faster data communications within local area networks, but intermodal dispersion effects limit the data rate on the standard optical fibre infrastructure in offices and factories. Two researchers from Universidad Politécnica de Valencia in Spain have combined low-linewidth distributed-feedback lasers with subcarrier multiplexing to send 10 simultaneous channels, each at 20 Gb/s, through 5 km of standard fibre network. The technique opens the possibility of radio-over-fibre transmission.

These eye diagrams show the waveform and quality factor Q of each of the 10 channels simultaneously transmitted over 5 km of multimode fibre. Courtesy of the Optical and Quantum Communications Group.

It involves 10 Exfo lasers that emit narrowband carrier wavelengths between 1540.56 and 1554.94 nm, which are combined by an Alcatel multiplexer. An Agilent data generator modulates the signal, and a single-mode fibre launches and recovers the light at either end of the 5-km multimode fibre, reducing modal dispersion and effecting mode filtering. An Accelink amplifier boosts each signal before detection. The authors demonstrated that the data transmission is free from error, and they achieved high-quality factors for each channel.

(Optics Express, 26 May 2008, pp. 8033-8038)