A Fiber optical gyroscope (FOG) is a precision sensor that measures angular velocity using the interference of light rather than mechanical components. Engineers typically use optical gyroscopes in aerospace, maritime, and navigation systems where high reliability and accuracy are essential.
Unlike traditional spinning-mass gyroscopes, optical gyroscopes contain no moving parts, which improves their durability and resistance to vibration and shock.
An optical gyroscope works using the Sagnac effect. This effect causes a phase shift when the system rotates. The system splits a light beam into two parts. One beam travels clockwise, and the other goes counterclockwise. Both beams move through a closed-loop optical fiber or a resonant cavity. Rotation causes a difference in travel time between the beams. This difference creates a measurable phase shift. The system uses this shift to calculate the rate of rotation.
If the system is stationary, both beams return to the detector at the same time and interfere constructively. However, when the system rotates, one beam travels a slightly longer path than the other, creating a measurable phase difference. The gyroscope converts this phase shift into a precise angular velocity reading.
There are two main types of optical gyroscopes: the Ring Laser Gyroscope (RLG) and the Fiber Optic Gyroscope (FOG). RLGs use laser beams within a triangular or square-shaped cavity made of mirrors, while FOGs guide light through long coils of optical fiber. FOGs tend to be smaller, lighter, and more rugged, making them ideal for mobile or space-constrained platforms.
These sensors play a key role in inertial navigation systems, where they help determine position, heading, and orientation without relying on external references like GPS. Their ability to function in GNSS-denied or harsh environments makes them indispensable in defense, aerospace, autonomous vehicles, and underwater navigation.
FOG – Fiber optical gyroscope
