Performance evaluation of a multiple optical link FSO–FSO

Abstract

Free-space optics (FSO) connects two distant points by a simple light beam. Currently, this technique is a complement to radio frequency systems and those based on optical fibers. However, its large-scale deployment is slowing down due to major drawbacks such as the short operating distance and its great vulnerability to atmospheric conditions. In this article, and in order to increase the connection distance of the FSO systems and maintaining an acceptable signal quality, we inserted in the transmission channel: a receiver and a transmitter that retransmit the received signal. We have chosen two weather situations. The attenuation values used are 85 dB/km and 170 dB/km. They represent two different fog densities. For an attenuation of 85 dB/km, the quality factor Q degrades and goes from the value 44.50 to 2.60 when the distance goes from 90 to 180 m. With the proposed technique, the quality factor has improved significantly since we obtained a value that is equal to 29.82 instead of 2.60 at the overall distance of 180 m. On the other hand, we increased the distance until we obtained a quality factor around 2.5. The distance obtained is equal to 360 m, which is twice the initial distance.