Time-domain measurements are carried out using arrangements and methods. A transmitter generates electro-magnetic pulses upon receipt of pulses of an optical pulse source. A coherent detector detects the electro-magnetic pulses or an evoked electro-magnetic signal. A delay line periodically changes the optical path length between the optical pulse source and the coherent detector and/or the electro-magnetic transmitter by periodically moving an optical element of the delay line. A position sensor determines the position of the optical element and smoothes the data generated by the position sensor. The coherent detector detects the electro-magnetic signal evoked by the electro-magnetic pulses. Pulses of the optical pulse source trigger the coherent detector. The time-dependency of the electro-magnetic pulses and/or of the electro-magnetic signal evoked by the electro-magnetic pulses are determined using signals of the coherent detector upon receipt of the electro-magnetic pulses and/or of the electro-magnetic signal and the smoothed position sensor data.