A method for measuring the timing jitter in a 1550 nm mode-locked fiber laser, with the help of an autocorrelator, has been developed and the error in measuring the value of the jitter has been evaluated. The preliminary results have shown that the fluctuations of the jitter are higher than the medium value of the jitter itself, so we decided to use some amplifiers in the circuit in order to eliminate this problem. The setup was changed by adding a laser diode, with the wavelength of 980 nm, and an erbium fiber. The medium value of the jitter we obtained (from eight measurements) for our setup was 78.8 fs. In order to still improve the measurements, we changed the time constant of the autocorrelator from 1.1 ps to 10 fs. The new medium value we obtained for the timing jitter was 78.33 fs. Finally, we calculated the error in measuring the timing jitter in our setup. We can say that the optical cross correlations present a powerful tool for characterizing the timing jitter in mode-locked fiber lasers.© (2009) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.