  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 $10^{-8}$ could be manipulated by
applying a giant dispersion to each tooth of the comb. Such coupling is
achieved with an intracavity etalon, resulting a large change in phase response
of a ring laser. This change is shown to be unrelated to the average pulse
velocity within the laser cavity.
