Rotation Active Sensors Based on Ultrafast Fibre Lasers

Gyroscopes merit an undeniable role in inertial navigation systems, geodesy and seismology. By employing the optical Sagnac effect, ring laser gyroscopes provide exceptionally accurate measurements of even ultraslow angular velocity with a resolution up to 10−11 rad/s. With the recent advancement of ultrafast fibre lasers and, particularly, enabling effective bidirectional generation, their applications have been expanded to the areas of dual-comb spectroscopy and gyroscopy. Exceptional compactness, maintenance-free operation and rather low cost make ultrafast fibre lasers attractive for sensing applications. Remarkably, laser gyroscope operation in the ultrashort pulse generation regime presents a promising approach for eliminating sensing limitations caused by the synchronisation of counter-propagating channels, the most critical of which is frequency lock-in. In this work, we overview the fundamentals of gyroscopic sensing and ultrafast fibre lasers to bridge the gap between tools development and their real-world applications. This article provides a historical outline, highlights the most recent advancements and discusses perspectives for the expanding field of ultrafast fibre laser gyroscopes. We acknowledge the bottlenecks and deficiencies of the presented ultrafast laser gyroscope concepts due to intrinsic physical effects or currently available measurement methodology. Finally, the current work outlines solutions for further ultrafast laser technology development to translate to future commercial gyroscopes.

Effects of temperature variations in high-sensitivity Sagnac gyroscope

GINGERINO is one of the most sensitive Sagnac laser-gyroscopes based on an heterolithic mechanical structure. It is a prototype for GINGER, the laser gyroscopes array proposed to reconstruct the Earth rotation vector and in this way to measure General Relativity effects. Many factors affect the final sensitivity of laser gyroscopes, in particular, when they are used in long-term measurements, slow varying environmental parameters come into play. To understand the role of different terms allows to design more effective mechanical as well as optical layouts, while a proper model of the dynamics affecting long-term (low frequency) signals would increase the effectiveness of the data analysis for improving the overall sensitivity. In this contribution, we focus our concerns on the effects of room temperature and pressure aiming at further improving mechanical design and long-term stability of the apparatus. Our data are compatible with a local orientation changes of the Gran Sasso site below $$\mu $$ μ rad as predicted by geodetic models. This value is consistent with the requirements for GINGER and the installation of an high-sensitivity Sagnac gyroscope oriented at the maximum signal, i.e. along the Earth rotation axes.

Passive ring laser gyroscopes to access fast variations in EOPs

<p>Quite generally, the Earth Orientation Parameters (EOPs) as obtained via VLBI and GNSS lack short-term sensitivity on (sub-)diurnal timescales. To access these fast dynamics, large <em>active</em> ring laser gyroscopes have been devised and are currently operated in geodesy and seismology. Here, we propose a novel type of gyroscope, namely <em>passive</em> ring lasers. By placing the gain medium outside of the optical resonator, the passive variant may remove many of the systematic limitations of active gyroscopes, and holds the potential to increase sensitivites by two orders of magnitude. Interfacing the gyroscopes with our optical clock technology will improve long-term stability as well. We will report on preliminary work and on the design and anticipated performance parameters of two demonstrators, as put forward by a recently established European collaboration.</p>

Main characteristics and perspectives of development of laser gyroscopes

Nowadays unmanned aerial vehicles (drones) are applied for solution numerous remote sensing tasks. They give a new opportunites for conducting environmental monitoring and give images with a very high resolution. Unmanned aerial vehicles are applied for solution numerous agricultural problems. They give a detail picture of fields. Unmanned aerial vehicles are used to help increase crop production. With technology constantly improving, imaging of the crops will need to improve as well.Digital images obtained by unmanned aerial vehicles (drones) can be used in forestry, they are used for environmental monitoring, plant health assessment and analysis of natural disasters. Unmanned aerial vehicles are also used for mining, they are applied for mapping deposit sites, exploring for oil and gas, surveying mines.Laser gyroscope is an essential component of a drones flight control system. Laser gyroscopes provides orientation control of drone and essential navigation information to the central flight control systems. Laser gyroscopes provide navigation information to the flight controller, which make drones easier and safer to fly. Laser gyroscope is one of the most important components, allowing the drone to fly smooth even in strong winds. The smooth flight capabilities allows us to get images with high precision.Nowadays the main function of gyroscope technologies is to improve the unmanned aerial vehicles flight capabilities. It was described a structure and main characteristics of laser gyroscopes. It was noted, that laser gyroscope is operated on the principle of the Sagnac effect. Sagnac effect is a phenomenon encountered in interferometry that is elicited by rotation. It were described main advantages and disadvantages of laser gyroscopes. A comparative analysis of mechanical and laser gyroscopes was carried out too.It also was noted, that laser gyroscopes are applied in different areas, such as: inertial navigation systems, aircraft, ships, unmanned aerial vehicles (drones) and satellites. Nowadays laser technology is developed further. There are all prerequisites for improving the precision and other technical characteristics of laser gyroscopes.

Mode locking suppression in a magneto-optical gyro

Integrated ring laser gyroscopes are perfect candidates for small-sized and high-performance gyroscopes. However, the performance of the ring laser gyroscope (RLG) near zero angular velocity is fundamentally restricted by the mode locking effect. In the paper the magneto-optical ring resonator is studied as a sensitive element of the integrated RLG. The counter-propagating waves are generated at the same frequency for resonator at rest and are spatially split. It is shown that the spatial splitting of modes in such a resonator drastically suppresses the mode locking problem even at the near zero angular velocity.

Optimizing Strap-down Inertial Navigation Systems Characteristics and External Correction Sensors for Autonomous Navigation of Different UAV Classes

Currently, unmanned aerial vehicles (UAVs) can be used in topographic works, condition monitoring and diagnostics of extended engineering structures, delivering goods to hard-to-reach places, etc. To provide the widespread UAVs applications and raise the number of tasks to be solved through their using, it is necessary to increase their autonomy degree in terms of navigation support, in particular. Unmanned aerial vehicles (UAV) control systems for autonomous navigation use the strap-down inertial navigation systems (SINS) based on various types of gyroscopes. SINS based on the laser gyroscopes, which have a large mass, have the best accuracy. UAVs with a payload mass that is commensurable with the mass of navigation equipment require optimization of SINS characteristics. An optimization method has been developed to enable obtaining a Pareto set for the mass and accuracy of SINS based on laser gyroscopes. A comprehensive assessment of the characteristics of SINS and UAV carrier with different payload mass has been performed. Various SINS correction methods are considered when satellite navigation is unavailable.For overland flights, the correlation-extreme navigation systems (CENS) and SLAM methods (for simultaneous localisation and mapping) can be used. CENS require a reference lay-of-the-land description and a sufficient density of landmarks. In navigation based on SLAM algorithms, there is no need in the reference lay-of-the-land description, and the initial data can be obtained through the optical sensors under appropriate condition of the atmospheric path.Regardless of the condition of the atmospheric path, type of the underlying surface and its information available in detail, the UAV coordinates can be determined by Doppler dead reckoning using a Doppler system (DISS). At low and medium altitudes SINS correction is possible, only heading sensor data are needed to calculate the path angle.In combining with DISS and 3D Flash Ladar sensors (for implementing SLAM algorithms), it is more optimal to use low-accuracy SINS based on fibre-optic gyroscopes rather than laser gyro-based systems.The results obtained can be used when developing navigation systems for medium, light and heavy-medium UAVs.