Rotational rate comparator for a fiber optic gyroscope with a 3.times.3 coupler

A rotational rate comparator for a fiber optic gyroscope with a 3.times.3 coupler, for calculating a rotational rate from photodiode signals of the fiber optic gyroscope, said comparator comprising an electrical circuit that is independent of an evaluating computer, said electrical circuit including discrete logic components that embody an algorithm for producing at least one rotational rate signal that is dependent on the rotational rate based on signals from the photodiode, and said electrical circuit generating an output signal when said rotational rate signal exceeds at least one presettable limiting value;

• wherein the following inequalities are embodied in the electrical circuit:
• .vertline.P.sub.2 -P.sub.3 +k(P.sub.2 +P.sub.3).vertline.<L1(P.sub.2 +P.sub.3),
• connected by a logical AND link with one of the following
• P.sub.2 +P.sub.3 >L2,
• n(P.sub.2 +P.sub.3)>L2,
• and
• n'(P.sub.2 +P.sub.3)>L2.P1
• where
• P1=signal from a monitor diode of the fiber optic gyroscope,
• P2=signal from a second photodiode of the fiber optic gyroscope,
• P3=signal from a second photodiode of the fiber optic gyroscope,
• k, n, n'=constants,
• L1=limiting value of maximum or minimum rotational rate, and
• L2=limiting value for excluding the rotational rate of zero.