An inclinometer for determining the azimuth of the borehole using a fiber optic gyro element. Although the fiber optic gyroscope is called a gyroscope, there is no mechanical gyro rotor in the component. The fiber optic gyroscope is actually an angular velocity sensor based on the Sagnac effect. The Sagnac effect is: When the beam advances in an annular channel, if the annular channel itself has a rotational speed (angular velocity), then the time required for the light to travel in the direction of the channel rotation is greater than the direction of rotation of the channel. It takes more time to move forward. That is to say, in the two forward directions, the optical paths of the two beams change with respect to the optical path of the channel at rest.
An interferometric fiber optic gyroscope can be fabricated by interfering with two beams propelling in different directions to measure the rotational speed of the loop. If the change of the optical path of the loop is used to realize the interference between the light circulating continuously in the loop, that is, by adjusting the resonant frequency of the light of the optical fiber loop and measuring the rotational speed of the loop, the resonance can be manufactured. Fiber optic gyroscope. Fiber optic gyroscopes have high accuracy and sensitivity. More advanced fiber optic gyroscopes have now reached a sensitivity of 0.01 degrees per hour. Compared to silicon micromachined gyros, the angular velocity sensitivity is several orders of magnitude higher. Using its high sensitivity to angular velocity, we can use it to measure the angular velocity vector of the Earth's rotation, and then calculate it to determine the tilting orientation of the borehole. This orientation is the orientation relative to the Earth's north pole. Some people call it the true north corner. This kind of gyro inclinometer is called the self-seeking north gyro inclinometer, and it is the best level and most widely used inclinometer (geology instrument).
If you want to get more details about inclinometer,pls visit https://www.ericcointernational.com/north-finding-system/north-seeking-gyro/