Fiber-Optical Gyroscopes
A fiber-optic gyroscope (FOG) is an optical device for sensing the changes in orientation, and thereby performing the function of a mechanical gyroscope, and for its operation is based on the interference of light having passed through a coil of optical f
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Fiber-Optical Gyroscopes
2.1 Introduction A fiber-optic gyroscope (FOG) is an optical device for sensing the changes in orientation, and thereby performing the function of a mechanical gyroscope, and for its operation is based on the interference of light having passed through a coil of optical fiber of very large length ~5 km. The advent of the diode lasers and low-loss singlemode optical fiber for the telecommunications industry led to the use of the Sagnac effect in the fiber-optic gyros (FOGs) in the form of the development of the practical devices in the beginning of this century [1–3]. Also termed as the interferometric fiber-optic gyroscope (IFOG), it is at present considered as an important option for various applications including the inertial navigation and guidance systems for aircraft, space industries, and helicopter attitude control. The success of this device has been due to its inherent advantages of solid-state technology, i.e., guided-wave optics and low-voltage low-power electronics, which have resulted in the cost reduction, and thereby enlarging the spectrum of its applications. IFOGs are based on the Sagnac effect, i.e., the production of a phase difference proportional to the dot product of the rotation rate vector by the area vector enclosed by the optical path, in a ring interferometer and, hence, has the advantage of single-mode optical fiber as the propagation medium. The FOG performance is affected by various critical system components and design characteristics, the most important of which are the coil optical fiber; the active source; the passive and integrated-optics components; and the detection systems. It is now known that the ring laser gyroscope (RLG), at present, is well established in the medium and high-performance markets, since it has many advantages over mechanical gyros like: digital output linear with angular rotation, high sensitivity and stability, quick reaction times, and insensitivity to acceleration and immunity to most environmental effects. Still, the RLG is considered as a specialized instrument whose utility varies with the application, and several factors limit its selection over modern mechanical system, namely: The exacting cavity geometries and precision mirrors required for RLG construction and the necessity of assembly under stringent © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021 K. N. Chopra, Optoelectronic Gyroscopes, Progress in Optical Science and Photonics 11, https://doi.org/10.1007/978-981-15-8380-3_2
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2 Fiber-Optical Gyroscopes
clean room conditions, driving its cost very high, bigger size, and larger weight of the RLG, as the solid glass optical block and mechanical dither assembly found in most RLGs unavoidably add to their weight. Because of these limitations, development of the fiber-optic gyros has picked up. Two main classes of fiber-optic gyros under development are: the interferometric fiber-optic gyro (IFOG) and the resonant fiberoptic gyro (RFOG). The RFOG
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