Integration of FSO in local area networks - Combination of Optical Wireless with WLAN and DVB-T for last mile internet connections

摘要

Nowadays FSO (Free Space Optics) also called Optical Wireless, is a well-established technology for closing the last mile gap. Optical Wireless is best suited to be directly connected to fibre optics, like the extension of a fibre cable for access networks. But also combinations with RF- and wireless networks are of main interest in current applications. Various technologies have different influences on weather conditions, because of the used wavelengths (frequencies) and the differences in the propagation behaviour and the transmission channel. This contribution will show at first the selection of best suited wavelengths for optical wireless communications (OWC) for the last mile access in relevance to the weather effects and the influences of beam divergence and beam shaping. The second part is showing the usage of FSO in combination with other wireless technologies (as a special scenario with WLAN and DVB-T), available for regions of low Internet coverage. FSO allows a broadband access with high data rate for users not connected so far by fibre cables. It is a well-known fact that peripheral regions lack of reasonable broadband Internet services. WLAN and FSO are license-free transmission technologies and DVB-T has become a geographically widespread technology. This paper will show an alternative Internet access method using WLAN and FSO systems as a data uplink and DVB-T as a downlink channel for broadband data access. The work was carried out within international co-operations in the frame of a special programme of European Union called SEE (South-East-Europe).