Connection of data networks (LAN) directly through the atmosphere using infrared light

摘要

Interconnection problems arise when local area networks (LAN) are expanded over larger distances. Today's solution is to lay cables, but their installation generally involves high costs. Different optical links for wireless data transmission are available. Data from a LAN are converted into light impulses using a semiconductor laser. This is possible up to data rates of more than 155 Mbps. After directed transmission via the atmosphere, an optical receiver detects the light flashes and converts them back into electric signals. The whole system can therefore be regarded as an optical radio relay system. In comparison to transmisson by wire, it offers a flexible alternative at low cost. This article describes first the theoretical background and then two different systems of the german company CBL. A very important point is the reliability due to the weather, which can be calculated on the basis of systems performance data. Experience gained from more than 100 installed systems in Germany are also reported: network coupling of Ethernet, Token-Ring, FDDI, voice (G.703) and voice and data mixed.