Fibre optic gyroscope
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A fibre optic gyroscope (FOG) is a gyroscope that uses the interference of light to detect mechanical rotation. The sensor is a coil of as much as 5 km of optical fiber. Two light beams travel along the fiber in opposite directions. Due to the Sagnac effect, the beam traveling against the rotation experiences a slightly shorter path than the other beam. The resulting phase shift affects how the beams interfere with each other when they are combined. The intensity of the combined beam then depends on the rotation rate of the device.
A FOG provides extremely precise rotational rate information, in part because of its lack of cross-axis sensitivity to vibration, acceleration, and shock. Unlike the classic spinning-mass gyroscope, the FOG has virtually no moving parts and no inertial resistance to movement. The FOG typically shows a higher resolution than a ring laser gyroscope but also a higher drift and worse scale factor performance. It is used in surveying, stabilization and inertial navigation tasks.
FOGs are designed in both open-loop and closed-loop configurations.
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