Optical gyroscopes are typically laser-based, and utilize a physical phenomenon called the Sagnac effect [14]. When two optical beams propagate in opposite directions in a rotating ring path, their propagation time, i.e., the time for the beam to return to its starting point, will differ fractionally; the beam that travels in the same direction as the rotation will take longer to return to the starting point than its counterpart, as shown in Figure 2.13. The angular velocity applied to the ring can be deduced by measuring the phase difference of the beams.
