Abstract: System and a method for eliminating external light interference effects in an active tracking equipment for free space optics communication, wherein a sample of an incoming light is received by a quad cells device (3) which outputs quadrant components of voltage values indicative of deviations of the incoming (IL; IL1) beam in different directions. The output of said quad cells device is filtered by a high pass filter (5) for blocking DC components as well as frequency components lower than a predetermined value from the out of the quad cells device (3), the output of the filter (5) being indicative of the position of incoming light (IL; IL1) with respect to the receiver (1).

Abstract: Method for receiving/trasmitting an optical signal through the air, the method comprising the steps of: providing a first free space optics apparatus; providing a second free space optics apparatus, the first and second apparatuses being spaced by a certain distance; at the first apparatus, transmitting an optical signal through the air at a bit-rate; receiving, at the second apparatus, said optical signal transmitted through the air by the first apparatus. The method being characterized by further comprising the steps of: measuring the power level of the received signal; and operating a switch for accomodating the bit-rate in order to change the fading margin in the apparatus. A lower bit-rate being used when the level of the received power is low and/or in rather bad weather conditions.