Disclosed is a method for determining/compensating the bias errors/random walk errors induced by the light source (1) in fiber-optic Sagnac interferometers using a modulation process for the stochastically independent displacement of the operating point to the points of maximum sensitivity. According to the inventive method, a reference beam is decoupled from the light beam that is emitted by thelight source of the interferometer and propagates in the direction of the fiber coil, a reference intensity signal which is proportionate to the intensity of the reference beam is generated, the reference intensity signal is demodulated by using the demodulation pattern used in the rotational speed control loop (7, 13) for demodulating the rotational speed intensity signal that is proportionate to the rotational speed, whereby a demodulated reference intensity signal is obtained which represents a measurement of the bias errors/random walk errors that are to be determined. The reference intensity signal is demodulated in synchrony with the rotational speed intensity signal in such a way that the signal portions of the reference intensity signal and the rotational speed intensity signal, which result from fractions of light simultaneously emitted by the light source (1), are demodulated in an identical manner.