Fiber optic gyroscopes (FOGs)

Fiber optic gyroscopes (FOGs) have many important applications in navigation and positioning systems, angular velocity sensors, stabilization equipment, and recently, in autonomous vehicle guidance backup systems for GPS-inaccessible areas. In an optical gyroscope, two counter-propagating optical beams are brought into interference in a Sagnac interferometer after travelling around a fiber-optic loop. The gyroscope system determines the rotation rate by measuring the net phase difference between the two beams, which is proportional to the rotation rate.

A high performance fiber gyro system must be able to accurately detect phase differences due to rotation, while minimizing or being able to compensate for phase differences due to other sources, such as temperature effects. In a FOG system, the sensing element is an optical fiber coil. Minimizing causes of phase errors in the coils reduces design complexity and improves the performance of the entire system, and increasing coil uniformity aids in standardization for mass production.