The invention concerns shutting down and restarting optical amplifiers, such as Raman amplifiers, in an optical link, depending whether the optical amplifier is a transmitting side amplifier or a receiving side amplifier. For controlling the amplifiers, at least one diagnostic signal is to be transmitted via an auxiliary optical channel in the optical link, and a number of physical events simultaneously taking place are to be taken into account to conclude whether to shut down or to restart one of the optical amplifiers.