Moving up the frequency spectrum
To support a wide spectrum of multimedia and new value added services, next-generation access networks require broad-bandwidth connections of large data transmission capacity at low cost. ROF technology emerged as a promising solution for serving both fixed and mobile users in a unified platform. ROF is a hybrid system consisting of heterogeneous networks formed by wireless and optical links. This technology makes it possible to centralise the signal processing functions at one central station and then use optical fibre links to distribute radio frequency signals to remote antenna units. This was the architecture pursued within the EU-funded project 'Wireless and wireline service convergence in next generation optical access networks' (WISCON). Researchers developed new techniques to produce carrier signals with wavelengths of a few millimetres, using photonic generation. The millimetre-wavelength region of the electromagnetic spectrum corresponds to frequencies on the order of 30 up to 300 GHz. Wireless communication systems operating at more than 60 GHz are expected to reach data transfer rates as high as 10 gigabits per second. By means of wavelength-division multiplexing, carrier signals are assigned to specific wavelengths with a designated frequency band and then multiplexed onto optical fibres. This process allows for multiple video, audio and data signals to be transmitted over one channel while maintaining system performance. The WISCON project was successfully completed with the experimental demonstration of millimetre-wavelength signal generation up to 87.5 GHz and distribution of multiple signals over a hybrid optical-wireless channel. This initial research work is currently being followed up in the EU-funded project FENDOI.
Keywords
Radio-over-fibre, communication networks, wireless, optical access networks, wavelength-division multiplexing
