  We consider the optical Sagnac effect, when the fictitious gravitational
field simulates the reflections from the mirrors. It is shown that no
contradiction exists between the conclusions of the laboratory and rotated
observers. Because of acting of gravity-like Coriolis force the trajectories of
co- and anti-rotating photons have different radii in the rotating reference
frame, while in the case of the equal radius the effective gravitational
potentials for the photons have to be different.
