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: A receiver for an optical transmission system in air is described. The receiver includes at least one receiving lens for focusing a beam received from a remote transmitter and a detector. The receiver is characterised in that it includes a portion or section of tapered optical fibre inserted basically into the focal plane of the at least one receiving lens. A method for increasing the gathering area in a receiver for an optical transmission system in air is also described.