A Rate Integrating Fiber Optic Gyro

In the past, fiber optic gyros have generally been viewed as angular rate sensors. However, for inertial navigation purposes, a "rate integrating" gyro characteristic is desired. The distinction is subtle, but important. A rate gyro's output represents an estimate of instantaneous angular rate. The system attitude is determined by sampling the rate and integrating numerically to angular displacement. On the other hand, a rate integrating gyro provides the change in rotation angle rather than instantaneous rate. The system accumulates the angular increments obtained from the gyro to determine rotation angle and, hence, attitude. A ring laser gyro is a good example of a rate integrating sensor. Its output consists of pulses that represent fixed angle increments. It is shown that an interferometric fiber optic gyro can also be configured as a rate integrating gyro. The paper discusses the theory and application of this concept.