Fiber optic gyroscope

The basic concept of fiber optic gyroscope

Modern fiber optic gyroscope is an instrument that can accurately determine the orientation of moving objects, it is an inertial navigation instrument widely used in modern aviation, navigation, aerospace and defense industry, its development has very important strategic significance to a country’s industry, national defense and other high-tech development.

Definition of fiber optic gyro

Fiber optic gyroscope is a sensitive element based on optical fiber coils. The light emitted from the laser diode propagates in two directions along the optical fiber. The difference of light propagation path determines the angular displacement of the sensitive element.

The advantages of fiber optic gyroscope compared with traditional mechanical gyroscope are all solid state, no rotating parts and friction parts, long life, large dynamic range, instantaneous start, simple structure, small size and light weight. Compared with laser gyroscope, fiber optic gyroscope has no latching problem and does not need to precision machine the optical path in quartz block, so the cost is relatively low.

Fiber optic gyro basic working principle

The implementation of fiber optic gyroscope is mainly based on the Segnick theory: when the light beam travels in a ring-shaped channel, if the ring channel itself has a rotation speed, then the time required for the light to travel in the direction of the channel rotation is more than the time required to travel in the opposite direction of this channel rotation. This means that when the optical loop is rotating, the light range of the optical loop changes in different directions of travel with respect to the light range of the loop at rest. Using this change in the optical range, the phase difference between the two optical loops or the change in the interference fringe is detected, and the angular velocity of the optical loop rotation can be measured, which is the working principle of fiber optic gyroscope.

Segnick’s theory introduction

The Seignik theory says that when a light beam advances in a loop, if the loop itself has a rotation speed, then it takes more time for the light to advance in the direction of the rotation of the loop than it does to advance in the opposite direction of the rotation of the loop.

This means that when the optical loop is rotating, the light range of the optical loop changes in different forward directions relative to the light range of the loop at rest. By using this change in optical range, if interference is generated between the light advancing in different directions to measure the rotation speed of the loop, an interferometric fiber optic gyroscope can be created. If you use this change in the optical path of the loop to achieve the interference between the light circulating in the loop, that is, by adjusting the resonant frequency of the light in the optical fiber loop and then measuring the rotation speed of the loop, a resonant fiber optic gyroscope can be manufactured.