A device for measuring the profile of single optical pulses includes an optical fiber loop (1, F) for creating a series of replica pulses (Ri) of the initial optical pulse, starting from the initial optical pulse (I), an automatic gain control (2, 3, 4, AMP) for adjusting the amplitudes of replica pulses (Ri) to values substantially the same as each other, an optical sampler (7, Ech) for forming optical samples (Ei) starting from replica pulses (Ri), and a detector (D) for forming an electrical signal from the optical samples (Ei). The device is applicable to measurement of single optical or electrical pulses or pulses with a low repetition rate.