Method for non-reciprocal transmission of electromagnetic radiation beam intended to transmit the EMR beam forward and prevent reverse transmission by directing the forward and reverse propagating EMR beams along different paths, characterised by the following steps: a) inputting the EMR beam through any preselected path of input/output paths (1, 2, 3, 4) into a rotating ring interferometer, which rotates at the angular velocity Ω; b) splitting the EMR beam inside the rotating ring interferometer into two equally or nearly equally intensive counter-propagating EMR beams travelling along counter-paths and inside the interferometer and because of the Sagnac Effect the phase shift of ±Pi/2 + m Pi radians, where m is any integer number, is induced between two split counter-propagating EMR beams, which may be either positive or negative, with respect to the phase shift m Pi, depending on the direction in which the counter-propagating EMR beams travel along the counter-paths and with regard to the rotation direction of the rotating ring interferometer; c) inducing an additional phase shift of Pi/2+ n Pi radians, where n is any integer number, between the counter-propagating EMR beams inside the ring interferometer, which is not dependent on the direction in which the counter-propagating EMR beams propagate and results in a total phase shift of either Pi + (m + n) Pi radians or 0 + (m + n) Pi radians, between the counter-propagating EMR beams depending on the direction in which the counter-propagating EMR beams travel with regard to the rotation direction of the ring interferometer; d) combining of the counter-propagating EMR beams inside the rotating ring interferometer into one single EMR beam and outputting the single EMR beam from the rotating ring interferometer through different input/output path selected from the paths (1, 2, 3, 4) than the one through which the EMR beam is inputted into the rotating ring interferometer; and e) aligning at least two input/output paths of EMR beams preselected of the input/output paths (1, 2, 3, 4) with the rotation axis of the rotating ring interferometer and directing to respective input/output ports (21, 22, 23, 24). a) inputting the EMR beam through any preselected path of input/output paths (1, 2, 3, 4) into a rotating ring interferometer, which rotates at the angular velocity Ω; b) splitting the EMR beam inside the rotating ring interferometer into two equally or nearly equally intensive counter-propagating EMR beams travelling along counter-paths and inside the interferometer and because of the Sagnac Effect the phase shift of ±Pi/2 + m Pi radians, where m is any integer number, is induced between two split counter-propagating EMR beams, which may be either positive or negative, with respect to the phase shift m Pi, depending on the direction in which the counter-propagating EMR beams travel along the counter-paths and with regard to the rotation direction of the rotating ring interferometer; c) inducing an additional phase shift of Pi/2+ n Pi radians, where n is any integer number, between the counter-propagating EMR beams inside the ring interferometer, which is not dependent on the direction in which the counter-propagating EMR beams propagate and results in a total phase shift of either Pi + (m + n) Pi radians or 0 + (m + n) Pi radians, between the counter-propagating EMR beams depending on the direction in which the counter-propagating EMR beams travel with regard to the rotation direction of the ring interferometer; d) combining of the counter-propagating EMR beams inside the rotating ring interferometer into one single EMR beam and outputting the single EMR beam from the rotating ring interferometer through different input/output path selected from the paths (1, 2, 3, 4) than the one through which the EMR beam is inputted into the rotating ring interferometer; and e) aligning at least two input/output paths of EMR beams preselected of the input/output paths (1, 2, 3, 4) with the rotation axis of the rotating ring interferometer and directing to respective input/output ports (21, 22, 23, 24).