  In atom interferometers based on two photon transitions, the delay induced by
the difference of the laser beams paths makes the interferometer sensitive to
the fluctuations of the frequency of the lasers. We first study, in the general
case, how the laser frequency noise affects the performance of the
interferometer measurement. Our calculations are compared with the measurements
performed on our cold atom gravimeter based on stimulated Raman transitions. We
finally extend this study to the case of cold atom gradiometers.
