Provided is a burst mode optical receiver capable of accurately detecting an optical signal of minimum amplitude, by automatically controlling a gain of a pre-amplifier according to an amplitude of an input optical signal. The latter depending on its rotational position establishes a connection, on the one hand, between an inlet for waste gas to be cleaned and at least one first segment of the heat exchanger area, as well as between at least one second segment of the heat exchanger area and an outlet for cleaned gas. The reflection surfaces are capable of splitting the incident light beam into a plurality of reflected light beams. At a preset time, prior to the time the originator has specified for the data file to be processed, the processing entity performs a confirmation test.