Abstract: The invention relates to a method for the digital, bidirectional data transmission on an optical waveguide. For either direction of the data transmission, light pulses having the same frequency are used. The pulses to be transmitted are reduced from an original width T.sub.b to a width T.sub.r, the pulse-to-pause ratio T.sub.r (T.sub.b -T.sub.r) having to be smaller than one. The second transmitter/receiver unit is allowed to transmit during a reception pause (T.sub.b -T.sub.r) only. In order to achieve an optimum distribution of the optical pulses on the optical waveguide 3, the first transmitter/receiver unit 1 measures the timing on the optical waveguide 3 and causes, if required, by a modify signal, the second transmitter/receiver unit 2 to a modified transmission time of its optical signals. Thereby, a control loop is established, automatically achieving an optimum pulse distribution on the optical waveguide, within certain limits (FIG. 3 ).