It is well known that spinor wave functions change their sign under $2\ensuremath{\pi}$ rotation. Several experiments have used magnetic precession of neutrons to implement rotations. Here we propose an all-optical analog of this effect based on time-resolved optical interference in coupled optical microcavities. We show that feeding the coupled-microcavity system with a pair of phase-locked probe pulses, separated by precise delay times, provides direct information on the sign change of the transmitted field after one complete Rabi-like oscillation period.