Application of Fiber Optic Gyroscopes in Drilling and Drill Inclinometers-2

Modern fiber optic gyroscopes have been developed based on the sagnac theory. The main point of the sagnac theory is that when the light beam advances in an annular passage, if the annular passage itself has a rotational speed, then the time it takes for the light to travel in the direction of the passage rotation is faster than the direction of rotation in the opposite direction of the passage. It takes more time. In other words, when the optical loop rotates, the optical path of the optical loop changes with respect to the optical path of the loop at rest in different forward directions. With this change in the optical path, if the interference between the light traveling in different directions is made to measure the rotation speed of the loop, an interferometric optical fiber gyroscope can be manufactured.

The basic optics of fiber optic gyroscopes include light sources, couplers, polarizers, fiber coils, and detectors. Fiber optic gyro components are mostly semiconductor devices, which are connected to each other and directly soldered to a printed circuit board. The use of fiber optic gyros in petroleum instruments overcomes almost all of the shortcomings of mechanical gyros, such as poor vibration resistance, magnetic field changes, many drift torque factors, and the effects of ambient temperature. Fiber Optic Gyro is an azimuth sensor that is very suitable for gyro inclinometers. An important body defect of FOGs is that the component parts are expensive and have poor resistance to high temperatures. In order to ensure accuracy, more and more fiber turns are used, resulting in a relatively large volume. The solution is to install a high-efficiency thermos bottle to ensure that the maximum operating temperature of the fiber optic gyroscope is below 80° so that it can basically meet the measurement needs of well depth within 4000 meters. Corresponding to the well diameter limitation, the diameter of the optical fiber can be effectively reduced by changing the optical fiber winding method to meet the requirements placed in the drill pipe.

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