Explain the working principle of a fiber optic gyroscope.

Interference of Light: In a fiber optic gyroscope, a coherent light source, such as a laser, emits light that is split into two beams traveling in opposite directions along a coil of optical fiber wound in a closed-loop configuration.

Rotation of the Loop: When the FOG experiences angular rotation (gyroscopic motion) about its sensitive axis, the optical path length traveled by the light beams in the two directions changes. This is due to the rotation of the coil of optical fiber, causing one beam to travel a slightly longer path and the other to travel a slightly shorter path.

Sagnac Effect: As a result of the unequal optical path lengths, the light waves recombine at a photodetector after completing their respective paths. Due to the Sagnac effect, where the phase difference between the two light waves is proportional to the angular rotation rate of the coil, interference occurs between the light waves.

Interference Pattern: The interference between the light waves produces an interference pattern that is detected by the photodetector. This pattern contains information about the rotation rate of the FOG.

Measurement of Rotation Rate: By analyzing the interference pattern detected by the photodetector, the FOG determines the rotation rate of the coil of optical fiber, which corresponds to the angular rotation of the system about its sensitive axis.

Output Signal: The FOG generates an output signal proportional to the rotation rate, which can be processed and used to determine changes in orientation or angular velocity.

Accuracy and Stability: FOGs are known for their high accuracy, stability, and reliability. They offer advantages such as low noise, wide dynamic range, and immunity to external electromagnetic interference.