We provide the first detailed characterization of spectral hole patterns created by coherent pulse pairs of which the optical phases could be varied in a controlled manner. The pulse pairs form hole patterns with a period given by the inverse of the time between the leading edges of the pulses. The envelopes of the hole patterns reflect the Fourier transforms of the pulses and the phase difference of the pulses appears as a phase shift of the population gratings in the frequency domain. The data are analyzed with a theoretical model which includes the pulse spectra and temporal parameters, the pulse phases, non-linear excitation, dephasing times and laser jitter. © 1992.