Long gone are the days when the captains of ships went on a long voyage armed only with a compass and a map. Today, no ship or aircraft is conceivable without a modern navigation system that allows at any time to determine the exact position of the ship in space. Modern navigation systems use a number of different sensors to determine the position of a moving object: satellite navigation (GPS, GLONASS), gyroscopes, accelerometers, odometers, etc. However, experts know that an independent navigation system can be created only on the basis of inertial sensors such as gyroscopes and accelerometers.
Active development and continuous improvement of the element base of fiber and integrated optics in recent decades has led to the emergence of a new type of inertial angular displacement sensors – fiber optic gyroscopes (FOG). The main differences and advantages of FOG in comparison with mechanical gyroscopes are: the absence of moving parts, resistance to acceleration and vibration; short start-up time; high sensitivity in a wide range of rotational speeds; wide bandwidth; high linearity of the transfer characteristics; low power consumption; high reliability; long service life (decades); small size and weight. At present, vogs are used as the main sensitive element of inertial navigation systems, orientation systems and stabilization of objects in space.
The principle of Vogue is based on the Sagnac effect. The figure below shows the schematic diagram of such a device. Optical radiation from the source, passing through the X-coupler enters the input of the integrated optical circuit, is divided into two beams that propagate along the fiber-optic circuit in opposite directions. If the circuit is at rest, there is no phase difference between the beams (Δφs = 0). When the circuit rotates relative to the inertial frame of reference, a phase difference Δφs proportional to the rotational speed of the FOG occurs. Changing the phase difference leads to a change in the radiation power detected by the photodetector.
Despite the seeming simplicity of the principles of operation of the device and its high sensitivity to the angular velocity of rotation, at the same time extremely susceptible to various external influences, causing spurious signal and, consequently, to reduce measurement accuracy, so the problem of creating high-VOG is still relevant. Moreover, we can state the fact that only highly developed countries are able to produce such devices.
Since 2005, the research center of Light-Guide Photonics (SIC light-Guide Photonics) together with the Central research Institute "Concern "Electropribor" are working to create a fiber-optic gyroscope navigation accuracy class. In this work, the staff and students of the Department in 2007-2008 were developed and implemented prototypes of FOG, which includes an optical circuit, a modulation system, electronics and software. To solve each of these problems, a huge research work has been done, dozens of articles have been written and several patents have been obtained. It should be noted that several books and monographs are devoted to the issue of building FOG.
In 2013-2016 with the financial support of the Ministry of education and science of the Russian Federation (project No. 02.G25.31.0044) were aimed at preparing for the serial production of fog of accuracy class 0.01, and 0.001 o/h, which is the ITMO University in the face of the SIC Fiber Photonics was selected as the main performer of works for scientific research.
The expanding areas of application of Vogue require constant modernization and refinement of the device (reduction of mass and dimensional characteristics, expansion of the dynamic range, operating temperatures, permissible maximum shock loads, etc.) therefore, work on the project of FOG is constantly ongoing.