Intracavity phase interferometry is a phase sensing technique using mode-locked lasers in which two intracavity pulses circulate. The beat frequency between the two output frequency combs is proportional to a phase shift to be measured. A laser gyro is a particular implementation of this device. The demonstrated sensitivity of 10-8 of these devices could be manipulated by applying a giant dispersion to each tooth of the comb. It is shown that the resonant dispersion of a Fabry-Perot inserted in the cavity couples to the modes of the frequency comb, resulting in a large change in phase response.