We present results on a technique for characterizing a Gires- Tournois interferometer (GTI) using a lightwave component analyzer. This apparatus measures the transfer function of the GTI in the frequency domain. By measuring this transfer function for different wavelengths of a tunable laser, we find the parameters of the GTI. These parameters are the mirror reflectivities of the GTI and the distance between the mirrors. With these parameters, it is then possible to determine the dispersion of the GTI. With this technique, we have been able to caracterize GTIs with FSR of 16.5 and 60 GHz.