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The closed-loop method based on the Faraday effect is realized with a low coherence-noise resonator in resonance fiber optic gyro (RFOG). The resonator based on spun-fiber (SF) is designed and fabricated, which not only has the advantage of low coherent optical noises, but also has an outstanding circularly state of polarization (CSOP) maintaining ability that lays the foundation for the realization of a closed-loop method based on the Faraday effect. As the core component of the Faraday-based method, the Faraday coil is reasonably designed to meet the requirements of the sufficient frequency shift and power stability. In addition, the interval control method that is conducive to the improvement of system stability is applied to control Faraday coil for the first time. The experimental results show that the method we proposed can effectively achieve high-reciprocity and linear equivalent frequency shift by Faraday coil. Also, the short-term and long-term stability of Faraday-based RFOG system have been improved compared with other closed-loop methods, which provides a simple and efficient method for RFOG closed-loop signal processing.

The gyroscope is a device that makes it possible to measure the change in the orientation angles associated rotation of the body relative to an inertial coordinate system. Photonic crystal fiber gyroscopes are a kind of optical gyroscopes that offer many new features beyond that conventional fiber optic gyroscopes can offer. In any case, the properties of the optical fiber can play a large role in determining the characteristics of the gyroscope. The principle of operation of most optical gyroscopes is based on the Sagnac effect or the Sagnac interferometer, the essence of which is as follows. If two light waves propagate in a closed optical circuit in opposite directions, then in the case of an immovable circuit, the phase incursions of both waves that have passed the entire circuit in opposite directions will be the same. When the contour rotates around an axis normal to the contour plane, the phase incursions of the waves become unequal, and their difference in the general case will be proportional to the angular velocity of the contour rotation, the area covered by the contour, and the frequency of the electromagnetic wave (EMW). Since the area and frequency of the EMW remain unchanged during the operation of the gyroscope, the phase shift will be proportional only to the angular velocity. The use of photonic crystal fiber to increase the sensitivity is very promising; it significantly reduces the drift through thermal polarization, resistance, and the Kerr effect. This article suggests the use of photonic-crystal (hollow-core) fiber in optical gyroscope instead of conventional fibers.

In this article, a closed-loop signal detection method is proposed to improve the dynamic performance of the resonant integrated optical gyroscope. We firstly establish a closed-loop error model of the angular velocity tracking system with optical nonlinearity and parameter uncertainty based on triangular phase modulation technology. Then, we optimize the loop gains of the signal processing to improve the signal-to-noise ratio of the closed-loop error signal about angular velocity tracking. Secondly, we design a timing sequence control method to effectively eliminate the time-delay of signal processing for optimizing the dynamic performance of the angular velocity tracking system. Finally, a control algorithm is designed to suppress the influence of the optical nonlinearity and parameter uncertainty for improving the dynamic tracking performance of resonant integrated optical gyroscopes. The experimental results demonstrate that the resonant integrated optical gyroscope has a rise time less than 36 μs, a high frequency response with the bandwidth 13.1 kHz, and a low scale factor nonlinearity less than 269.2 ppm, which verifies the effectiveness of the proposed closed-loop signal detection method for the resonant integrated optical gyroscope.

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.

The quadratic Sagnac effect, recorded by an observer in the laboratory frame of reference (inertial frame), relative to which the Michelson interferometer moves, has been considered. The quadratic Sagnac effect was previously calculated in a rotating frame of reference, where it occurs as a consequence of the influence of the gravitational potential of the Coriolis force in the rotating frame of reference and leads to a phase difference in the rotating Michelson interferometer. It has been shown that the quadratic Sagnac effect values calculated in the inertial frame and rotating frame of reference are practically the same. It has also been shown that, in various cases, the calculation of the quadratic Sagnac effect is most rational to carry out either in the inertial frame or in the rotating frame of reference. The numerical estimates performed have shown that the experiments on recording the quadratic Sagnac effect are quite possible. The concept of effective lengths of the arms of a Michelson interferometer moving relative to a stationary observer: the light paths lengths during its propagation in the forward and backward directions, has been introduced. These effective arm lengths coincide with neither Michelson interferometer proper arm length $$L$$ nor its relativistic length $$L{\text{/}}\gamma $$ . The introduction of this concept is due to the fact that the moving Michelson interferometer mirrors move during the light propagation. In some calculations, it is advisable to take into account the Michelson interferometer effective arm lengths.

Modern gyroscopy is characterized by a great diversity of gyroscopes that have been and are being developed. Dominant positions belong to wave optic gyroscopes implementing the relativistic Sagnac effect, and micromechanical vibratory gyroscopes the operating principle of which is based on Coriolis effect. At the same time, high-precision rotor mechanical gyroscopes based on the principles of rotating solid body dynamics partially retain their position; also, the research of gyroscopes developed on the principles of nuclear physics and quantum optics is progressing successfully. Current state and the prospects of gyroscopes development are discussed in this paper.

This paper provides a scheme for realizing high-accuracy, low-cost resonant fiber optical gyroscopes (RFOGs) with single-mode (SM) fibers. The temperature-related polarization noise, which deteriorates the bias stability of the RFOG, has been suppressed thanks to a much longer birefringence beat length of SM fibers. It is also helpful to improve the theoretical sensitivity of the RFOG because of the very low loss of the SM fiber components. A transmissive 39-m-long SM fiber ring resonator (FRR) is fabricated. The measured finesse is 58.7, and its total loss is calculated to be less than 0.3 dB. Using this SM-FRR as the sensing element, an RFOG is then set up that achieves an angular random walk of 0.0039 ∘ / √ h and a bias stability of 0.05°/h. The experimental results show that the SM-FRR scheme would be a good candidate for producing high-accuracy and low-cost RFOGs.

We investigate theoretically nonreciprocal chaos in a spinning optomechanical resonator. We find that under the Sagnac effect induced by spinning a resonator, the chaotic motion can exhibit unidirectional behavior. More specifically, the chaotic motion takes place when the spinning resonator is driven in a chosen direction, whereas it cannot emerge when the driving laser is applied in the opposite direction. Moreover, due to the Sagnac effect, we show that nonreciprocal chaos can resist the backscattering losses. The underlying reason for these phenomena is that the Sagnac effect induces an opposite frequency shift between clockwise and counterclockwise optical modes. Our work opens up a new route to achieve nonreciprocal chaos with the current experimental technology and may provide theoretical guidance for the production of a directional chaos signal generator.

Optical gyroscopes based on the Sagnac effect have been the mainstay of inertial navigation in aerospace and shipping for decades. These gyroscopes are typically realized either as ring-laser gyroscopes (RLGs) or fiber-optic gyroscopes (FOGs). With the recent rapid progress in the field of ultrahigh-quality optical whispering-gallery mode and ring microresonators, attention has been focused on the development of microresonator-based Sagnac gyroscopes as a more compact alternative to RLGs and FOGs. One avenue that has been explored is the use of exceptional points in non-Hermitian systems to enhance the responsivity to rotation. We use a similar phenomenon, namely, the critical point of a spontaneous symmetry-breaking transition between counterpropagating light, to demonstrate a microresonator gyroscope with a responsivity enhanced by a factor of around 10 4 . We present a proof-of-principle rotation measurement as well as a characterization of the system’s dynamical response, which shows the universal critical behaviors of responsivity enhancement and critical slowing down, both of which are beneficial in an optical gyroscope. We believe that this concept could be used to realize simple and cheap chip-based gyroscopes with sensitivities approaching those of today’s RLGs and FOGs.

Traditional optical gyroscopes rely on the Sagnac effect that the resonant frequency shift is linear with the rotation rate. Recently, optical gyroscopes operating near an exceptional point (EP) have been extensively investigated to improve the response to rotation. However, the high-performance implementation of this kind of gyroscope requires strict conditions, which restrict the practical application of these devices. In this paper, a non-Hermitian photonic configuration based on a single resonator is proposed to establish an exceptional surface (EP surface) constructed of numerous EPs. It is demonstrated theoretically that rotation-induced frequency splitting in our configuration is four orders of magnitude higher than that in the traditional gyroscope. We also investigate the shot-noise-limited minimum detectable rotation rate compared to the conventional gyroscope with the same radius and intrinsic loss, when the system is tuned around the EP. This proposed approach attempts to combine robustness with high sensitivity detection of the rotation.

Gyroscopes play an important role in inertial navigation systems in ships, air- and space-craft [1] and astronomy [2] . However, the presence of the lock-in effect significantly hampers the further increase of their performance. Besides, modern self-navigation applications demand compactness with kHz data rates. Previous studies have demonstrated a potential of recently emerged time-stretch techniques, such as the Dispersive Fourier Transformation (DFT) [3] , [4] , for detection of the optical Sagnac effect through single-shot spectral measurements of ultrashort pulses [5] . In this work, we present a phase-based method to detect rotation in a passive all-fibre Mach-Zehnder interferometer (MZI) via assessing real-time dynamics of ultrashort pulses. Moreover, the lock-in effect is com-pletely eliminated since two pulses (reference and signal) are propagating in two different arms of the MZI. The resolution of the phase retrieval is 7.2 mrad that corresponds to an angular shift of 5.78 µ rad. The data rate is 15 MHz as determined by the repetition rate of the mode-locked laser used.

A theoretical study is performed of the sensitivity and quantum-noise limit of a passive coupled-ring optical gyroscope operated at and detuned from its exceptional point (EP) and interrogated with a practical conventional readout system. When tuned to its EP, the Sagnac frequency splitting is proportional to the square root of the applied rotation rate, but the signal generated by the sensor is shown to be proportional to the applied rotation rate. The sensitivity is never larger, and the minimum detectable rotation rate in the quantum-noise limit never lower, than that of a standard single-ring gyro of the same radius and loss, even when the coupled-ring gyro is tuned exactly to its EP. As pointed out elsewhere for other EP sensors, in this particular passive sensor at least, there is no sensitivity or resolution benefit in operating at an EP.

Optical gyroscopes are widely used for precision navigation and there has been growing interest in the possibility of integrated optical gyroscopes. In this talk, we report a chip-based Brillouin laser gyroscope with Earth-rotation-rate sensitivity.

Electronic analogs of optical interferences are powerful tools to investigate quantum phenomena in condensed matter. In carbon nanotubes (CNTs), it is well established that an electronic Fabry-Perot interferometer can be realized. Other types of quantum interferences should also arise in CNTs, but have proven challenging to realize. In particular, CNTs have been identified as a system to realize the electronic analog of a Sagnac interferometer---the most sensitive optical interferometer. To realize this Sagnac effect, interference between nonidentical transmission channels in a single CNT must be observed. Here, we use suspended, ultraclean CNTs of known chiral index to study both Fabry-Perot and Sagnac electron interferences. We verify theoretical predictions for the behavior of Sagnac oscillations and the persistence of the Sagnac oscillations at high temperatures. As suggested by existing theoretical studies, our results show that these quantum interferences may be used for electronic structure characterization of carbon nanotubes and the study of many-body effects in these model one-dimensional systems.

Fundamental limits of fiber link are set by non-reciprocal effects that violate the hypothesis of equality between forward and backward path. Non-reciprocal noise arises technically from the set-up asymmetry, and fundamentally by the Sagnac effect when the fiber link encloses a non-zero area. As a pre-requisite for observation of Sagnac effect in fiber links, we present a study on phase noise and frequency stability contributions affecting coherent optical frequency transfer in bi-directional fiber links. Both technical and fundamental limitations of Two-Way optical frequency transfer are discussed. Our model predicts and our experiments substantially verify that the dominant noise mechanism at low Fourier frequencies is the polarization asymmetry induced by the temperature and relative humidity variations impacted on fiber links. The flicker noise floor due to the non-reciprocal noise arising from polarization mode dispersion is evidenced for the first time. We perform a post-processing approach which enables us to remove this polarization noise, improve the long-term stability and remove a frequency bias. We evaluate the uncertainty contributions of all the effects discussed for our 50 km spooled fiber link, dominated by its non-reciprocal noise induced by polarization mode dispersion with uncertainty of 1.9( ± 0.8)( ± 1.2) × 10−20. After correction, the linear drift of the residual phase is as low as 27 yoctosecond/s, leading to an uncertainty of the frequency transfer of 2.6 ( ± 39) × 10−22, confirming its potential for searching for more fundamental effects such as Sagnac effect or transient frequency variation due to dark matter.

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.

This article provides a brief overview of the state-of-the-art development of a new generation of gyros on cold atoms for space applications. The problem of narrowing the dynamic range of atomic interferometers in comparison with optical interferometers and method for resolving this problem are discussed. Three new results are presented for the first time in the world: 1) A new “kinematic” gyroscopic principle that allows one to determine uniquely the absolute angular velocity without limitations on the measurement range, in contrast to the interferometric gyroscopic principle; 2) Accurate expressions of gyroscopic effects on cold atoms and on de Broglie waves based on kinematic and interferometric gyroscopic principles, which are fundamentally different from the Sagnac effect; 3) The asymmetry of the particle-wave duality seen in gyroscopy: an increase in the sensitivity to rotation when stepping from photons to cold atoms is colossally greater than the increase in sensitivity when stepping from light waves to de Broglie waves of the order of (1013 ÷ 107) at atom temperature of the order of (10−9 ÷ 10−3) K.

In order to meet new directions of research in the field of rotational seismology, a registration of rotation phenomena from mining seismic shocks was carried out by two interferometric optical systems. Applied instruments are based on the Sagnac effect and measure the rotation rate in a direct way. Systems have a wide measuring range both in the case of signal amplitude as well as frequency range. Allan variance analysis has indicated that they have proper parameters for the rotational seismology investigation (angle random walk equals 3.20 · 10−8 rad/√s, as well as bias instability equals 2.41 · 10−8 rad/s). Moreover, regarding applied special electronic processing, they provide rotation rate as an output instead of a change of an angle like in commercially available fiber optic gyroscopes. The optical head of the constructed systems uses depolarized light in order to avoid polarization effect. Systems are remotely controlled by the Internet and adapted to an independent power supply which makes them fully autonomous. Correlation between data gathered by two systems applied in a geophysical observatory in Ksiąz, Poland, have been calculated according to the person's correlation coefficient.

Optical gyroscopes play important roles in the field of angular velocity measurement. Improving the accuracy of the Sagnac effect is always an attractive research topic. In this work, a new scheme is proposed and demonstrated by using a polarization-maintaining bidirectional coupled optoelectronic oscillator (COEO) incorporating a Sagnac loop structure. In COEO resonant cavity, optical carrier and one of the first-order sidebands are separated by polarization delay interferometers, and propagate in opposite directions in the Sagnac loop. The rotation-induced phase difference between optical carrier and first-order sideband produces a frequency shift in COEO system. Moreover, for bidirectional system, the trends of resonant frequencies shift are opposite. Therefore, the difference of bidirectional resonant frequencies is the summation of unidirectional rotation-induced frequency shift. And less-complex, high-resolution microwave detection technology is used to improve the detection resolution of frequency difference. Therefore, a high-sensitivity angular velocity measurement system is implemented, with a sensitivity scale of 172.04 kHz/(rad/s). Theoretically, a minimally detectable angular velocity is 1.2 °/h.

The spectral Fourier–Bessel numerical solver is suitable for obtaining steady state modal properties for resonators and waveguides fitting a cylindrical geometry. The material properties and geometry of the structures are directly responsible for the optical properties of the states obtained. The solver computation domain is extended such that it can be used when the constitutive expressions include the magneto-electric coupling, bi-anisotropic. Full computation expressions required to populate the matrices are included along with three forms of the system matrix constructed from Faraday’s and Ampere’s curl relations. Two representative numerical computation examples are provided when axial rotation of the structure (Sagnac effect) is present; the resonator state properties of a uniform ring structure supporting whispering-gallery modes and a 6-fold rotationally symmetric deformed ring structure.

In this paper, we theoretically analyze the wavelength temperature stability of multifunctional integrated optical chips (MIOCs) applied on fiber optic gyroscopes (FOGs). This study is critical for improving the temperature stability of the FOG scale factor, which is a significant parameter used to evaluate the dynamic characteristics of FOGs. Analytical and multiphysics simulations uncover two significant new predictions. First, changes in environmental temperature can lead to misalignment of the coupling structure between the chip and fiber, which is the main reason for the deterioration of the MIOC wavelength temperature stability. Second, misalignment caused by temperature changes is related to the initial alignment parameters of the coupling structure. Therefore, we can effectively improve the wavelength temperature stability of an MIOC by correctly choosing the initial alignment state of the coupling structure. Space coupling experiments are also presented to verify these predictions, and the experimental and simulation results are in good agreement.

Operating an optical device at an EP causes small perturbations  applied to the device’s optical path length to produce a greatly enhanced splitting of resonance frequencies due to the splitting being proportional to  at the EP, instead of  as for conventional devices. For increasingly small  , the EP splitting can therefore be larger by several orders of magnitude by operating sufficiently close to the EP. This enhanced splitting has drawn great interest recently, in particular for the potential to miniaturize the optical gyroscope. However, a small but growing number of publications claim that EP sensors may not achieve a proportionally larger signal-to-noise ratio once the full readout system and noise is accounted for. Many different EP sensors have been proposed, some as passive resonators, others as resonators with internal gain operated either below or above lasing threshold. Each sensor class may use a different readout system to measure the splitting and is therefore subject to different noise, but the recent trend has been that once noise and readout system have been accounted for, the enhanced  response cancels out and a signal-to-noise ratio proportional to  is achieved. Despite this cancellation, enhanced precision in EP sensors has still been predicted, although there is disagreement in whether the enhancement arises from the EP or another aspect of the sensor’s architecture, such as the gain. In this paper, we demonstrate through simulations that the EP in two-coupled-mode resonant (below lasing threshold) gyroscopes plays no role in enhancing the signal-to-noise ratio. An all-passive EP gyro is simulated in the limits of shot noise and detector noise to show that in either of these noise limits, no improvement in SNR over the equivalent single-ring gyro is possible. One of the rings is then given gain to show that a large enhancement in detectornoise- limited SNR (~2400 fold) arises, but close proximity to the EP is not necessary to maximize this enhancement; the enhancement is actually significantly larger when the sensor is detuned from the EP. This gain-loss gyro is then compared to a single-ring gyro with gain to show that large sensitivity enhancements are possible in both architectures because the gain compensates the resonator loss, resulting in a narrowing of the resonance linewidth and a greater response to a rotation, but the coupled-ring gyro exhibits a much greater stability to gain fluctuations.

In a resonator micro-optic gyroscope (R-MOG), backscattering noise and Kerr noise have been key issues affecting the optical gyro output that are difficult to completely suppress. A method is proposed to suppress backscattering noise in a R-MOG. It uses two independent lasers and, by locking the two optical signals at different resonance peaks, a differential output of the two optical signals is achieved that successfully suppresses the backscattering noise. At the same time, a light intensity feedback loop based on a light intensity modulator is added to the loop to ensure the same optical power into the cavity. Experimental results show that the light intensity fluctuation into the gyro system is reduced nearly two orders of magnitude and the bias stability is improved to 9.06 deg/h by using a light intensity feedback loop with two independent lasers.

International audience; The quadrupolar winding of the sensing coil of a fiber-optic gyroscope (FOG) is an essential technique to reduce the thermal bias drift of this sensor. This technique, which is based on orthocyclic winding, contains complex nonaxisymmetrical zones, for example layer transitions or crossovers. In this paper, a precise topological reconstruction of the sensing coil is proposed using X-ray computed tomography. Thanks to this reconstruction, the first layer role and its impact on the next layers are studied. Then, the quality of the winding is quantified using interest parameters to evaluate crossovers and layer transition fibers. Finally, winding defects, particularly the propagation of gaps from layer to layer that causes sinking fibers, are highlighted.

Parity-time-symmetric optical gyroscopes are gaining interest for the enhanced sensitivity shown by exceptional points. The real splitting of anti-PT-symmetric gyroscopes is more reliable for stability and readout scheme than the complex splitting of parity-time-symmetric gyroscopes.

We model a gyroscope that exploits quantum effects in an atomic Bose-Einstein condensate to gain a tunable enhancement in precision. Current inertial navigation systems rely on the Sagnac effect using unentangled photons in fibre-optic systems and there are proposals for improving how the precision scales with the number of particles by using entanglement. Here we exploit a different route based on sharp resonances associated with quantum phase transitions. By adjusting the interaction between the particles and/or the shape of their trapping potential we are able to tune the width of the resonance and hence the precision of the measurement. Here we show how we can use this method to increase the overall sensitivity of a gyroscope by adjusting the system parameters as the measurement proceeds and our knowledge of the rotation improves. We illustrate this with an example where the precision is enhanced by a factor of more than 20 over the case without tuning, after 100 repetitions. Metrology schemes with tunable precision based on quantum phase transitions could offer an important complementary method to other quantum-enhanced measurement and sensing schemes., Comment: 10 pages, 4 figures

Utilizing the properties of exceptional points, we propose and demonstrate a new type of ring laser gyroscope on an active photonic integrated platform.

Due to increasing of accuracy requirements for the aircraft position determining by the using of autonomous navigation systems, the task of inertial system development becomes more and more urgent. In this paper considered the possibility of using of fiber optic gyroscope based on Sagnac effect and fiber optic accelerometers in Aircraft inertial systems. As shown in the paper, fiber optic gyroscopes allows small angles measurement more accurate than currently used ring laser gyroscopes. In addition these gyroscopes are chipper, more compact and reliable. Also using of fiber optic accelerometers in aircraft inertial system advantages are shown.

Dynamic performance is an important indicator of fiber optic gyroscopes, indicating the gyroscopes tracking ability in the state of large angular acceleration, such as overload, swaying, vibration. The Interferometric Fiber Optic Gyroscopes(IFOG) is based on the Sagnac effect and has the characteristics of nonlinearity, input saturation and time delay, etc. In general the IFOG’s closed-loop system is approximated as a linear system for modeling and analysis. This linear model is just suitable for the IFOG working in a static or uniform motion. In high dynamic conditions, the IFOG tracking error will appear strong nonlinearity and even become zero, which cannot be simply treated as linear model. Based on the analysis of the high dynamic tracking error characteristics of the IFOG, a semi-physical simulation method is proposed which can simulate the dynamic working environment of the IFOG under laboratory environment conditions. By equivalent external excitation to −π ~ +π phase, an arbitrary angular acceleration input is achieved. Comparing the external excitation and the IFOG output, the IFOG’s Dynamic response capability is truly reflected. Simulation show that it is beneficial in three aspects for improving the IFOG’s tracking ability. Firstly, reduce the delay time which is produced by data processing in the processor, Improve the rapidity of the IFOG’s response; Secondly, A dynamic modulation depth which is proportional to the tracking error technology can be implemented. Thirdly, the system feedback gain is combined of a optimal static gain and a optimal dynamic gain, which is decided by the tracking error.

We present a modified model for residual intensity modulation (RIM) observed in lithium niobate phase modulators, which is suitable for both narrow linewidth and wide linewidth lasers. This model is based on two key points leading to RIM: one is the optical propagation loss, which is proportional to the applied voltage, and the other is the interference between an injected wave and its reflection from the lithium niobate substrate. In order to verify the model, the RIM is measured accurately with different linewidths of input lasers respectively. The experimental results are in good agreement with the theoretical model as the values of fitting determination coefficient R-square are all above 0.995. The results have revealed that the chief reasons causing RIM are different. When using a narrow linewidth laser, the interference is the dominant reason leading to RIM as the ratio of the reflection-related coefficient including linewidth effects to optical loss reaches 34.33. However, the optical loss is the dominant reason leading to RIM with the ratio mentioned above reaching 0.31 when using a wide linewidth laser.

Thermal-induced errors have a significant impact on the environmental adaptability of a fiber optic gyroscope (FOG). Reasonable winding methods can reduce and offset the thermal-induced errors. However, complex methods put higher requirements on winding accuracy. By adding additional winding layers on the outer surface of the fiber coil, an improved winding method to reduce the temperature error of FOG is proposed in this paper. Simulations in temperature-control conditions and time-varying temperature conditions are performed. Simulation and experimental results show that additional winding layers lead to a satisfactory reduction of thermal-induced rate errors. With parameter estimation and error compensation, thermal-induced errors can be further reduced.

A novel fiber Sagnac-like detection system has unique competitive advantages for detecting atomic spin precession in atomic magnetometers. Unfortunately, its operating stability is severely limited by temperature fluctuations. In this paper, we describe a new approach to improve the temperature stability by using the ratio signal as the output instead of the conventional fundamental component. This method can effectively counteract the temperature-caused fluctuations in both light intensity and scale factor of photodetector. For a temperature range from 20°C to 40°C, a relative fluctuation of the ratio output signal of 0.97% was achieved, which was 17.4 times better than the fundamental component output. Moreover, no additional equipment and complex compensation algorithms are required during this process. It is a generic method that can also be applied to improve the stability of other detection schemes used in atomic magnetometers.

Generally, resonant optical gyroscopes (ROG) based on the Sagnac effect are very sensitive to the changes of temperature and optical power, which directly affects the output of the gyroscope. To improve the frequency lock-in accuracy and thermal stability of ROG system, the technology of laser frequency combination tuning and locking is proposed and experimentally demonstrated. Using the characteristics of voltage and temperature tuning wavelength of semiconductor laser, the output frequency range of laser is increased, the temperature control system of the resonant cavity can be removed and the gyro can never be unlocked in theory. In addition, the frequency lock-in accuracy under light power fluctuation is improved. Using this technique, a long-term (1-h) bias stability of 24.7 °/h is observed. Moreover, the weight and volume of the ROG are greatly reduced.

A non-Hermitian He-Ne ring laser gyroscope (RLG) that operates at an exceptional point is proposed and experimentally realized. Compared to a standard RLG, the device exhibits more than an order of magnitude enhancement in sensitivity.

Fiber-optic gyroscope comes under the category of optical gyroscopes which works on the principle of Sagnac effect. This paper provides a crux of fiber-optic gyroscope and its working principle. Fiber-optic gyroscopes work on the principle of the Sagnac effect. In Sagnac effect, the light beam is split into two separate beams. These beams then propagate in opposite directions with respect to each other. When the setup is stationary, the beams travel in same path and reach the output without any delay, if the setup is rotating, then one beam travels less distance than the other beam, and at output these beams arrive at different time and undergo interference to produce a fringe pattern which is sensitive to the phase difference between the beams. Fiber-optic gyroscope works on the similar basis, with a difference that the beams are made to travel within an optical fiber. These beams are obtained by passing light through a coupler and launched into the fiber using a collimator. Fiber-optic gyroscope is majorly used in military and aeronautical-based applications.

We present a cold atom gyroscope based on the Sagnac effect for matter-wave with very large area of 11 cm2 with record sensitivity and preliminary study of the scaling factor.

It is well known that different optical techniques can be used to measure angular velocities. Interferometric Optical Gyroscopes (IFOGs) and Ring Laser Gyroscopes (RLG) exploit the Sagnac effect and are the preferred solutions for tactile grade applications. However, in the Sagnac effect the measured output is directly proportional to the gyroscope sizes. So, the miniaturization and the integration of optical gyroscopes is still a challenge in optoelectronics research. In this paper different approaches based on parity-time and anti-parity-time symmetry are explained and compared as highly performance solutions for the integration of optical gyroscopes. The sensitivity of the rotation-induced frequency-splitting (broadening) can be several orders of magnitude higher than the classical Sagnac splitting achieved with a single ring gyroscope occupying the same surface. We will show that anti-parity-time-symmetric solutions represent a better choice for angular velocity sensing.

Angular- rate sensing can be achieved by monitoring the shift in or splitting of a resonant frequency. The mode-shift mechanism, described by the Sagnac effect, treats backscattering as a noise source in a traditional resonant optic gyroscope. While in an ultrahigh-Q resonator, backscattering can create mode splitting. Mode splitting as a self-reference sensing scheme can solve problems such as temperature vibration, which leads to a higher resolution. We propose the mode-splitting mechanism for angular-rate sensing. It is found that the angular rate can be derived from the amount of splitting instead of the frequency difference between the clockwise and counterclockwise waves. The theoretical highest resolution can reach 0.0614°/s. To realize enhanced performance, the issues that may affect the measurement are discussed.

We show that the lasing threshold for two coupled resonators (CRs) corresponds to lasing without gain (LWG), a phenomenon analogous to lasing without inversion in atomic systems, when parity-time (PT) symmetry is broken. The use of LWG for gyroscopes may resolve some of the difficulties associated with PT-symmetric gyroscopes. In particular, we find that PT-symmetric systems suffer from undamped Rabi oscillations, whereas LWG systems are overdamped. In addition, observation of enhanced sensitivity should be more straightforward in LWG gyros because the enhancement remains above unity even at couplings far from the exceptional point (EP). Finally, LWG gyros operate more like conventional laser gyroscopes with one frequency for each output direction, and therefore there is no ambiguity in the direction of rotation. Gain saturation in CR systems is found to dramatically boost the size of the sensitivity enhancement, eliminate the Rabi oscillations, and enlarge the parameter space around the EP over which the enhancement is expected to occur. A second situation with broken symmetry is also examined: CR systems below threshold. Whereas the pole in sensitivity coincides with the EP at threshold, the pole can occur far away from the EP for subthreshold systems. Our analysis also puts previous results on passive and active fast-light cavities using atomic vapor cells into the context of EP-enhanced sensing with non-Hermitian Hamiltonians.

Gyroscopes play a crucial role in many and diverse applications associated with navigation, positioning, and inertial sensing [1]. In general, most optical gyroscopes rely on the Sagnac effect -- a relativistically induced phase shift that scales linearly with the rotational velocity [2,3]. In ring laser gyroscopes (RLGs), this shift manifests itself as a resonance splitting in the emission spectrum that can be detected as a beat frequency [4]. The need for ever-more precise RLGs has fueled research activities towards devising new approaches aimed to boost the sensitivity beyond what is dictated by geometrical constraints. In this respect, attempts have been made in the past to use either dispersive or nonlinear effects [5-8]. Here, we experimentally demonstrate an altogether new route based on non-Hermitian singularities or exceptional points in order to enhance the Sagnac scale factor [9-13]. Our results not only can pave the way towards a new generation of ultrasensitive and compact ring laser gyroscopes, but they may also provide practical approaches for developing other classes of integrated sensors., 15 pages

The Sagnac effect, named after its discoverer, is the phase shift occurring between two beams of light, traveling in opposite directions along a closed path around a moving object. A special case is the circular Sagnac effect, known for its crucial role in GPS and fiber-optic gyroscopes. It is often claimed that the circular Sagnac effect does not contradict special relativity theory (SRT) because it is considered an accelerated motion, while SRT applies only to uniform, non-accelerated motion. It is further claimed that the Sagnac effect, manifest in circular motion, should be treated in the framework of general relativity theory (GRT). We counter these arguments by underscoring the fact that the dynamics of rectilinear and circular types of motion are completely equivalent, and that this equivalence holds true for both non-accelerated and accelerated motion. With respect to the Sagnac effect, this equivalence means that a uniform circular motion (with constant w) is completely equivalent to a uniform rectilinear motion (with constant v). We support this conclusion by convincing experimental findings, indicating that an identical Sagnac effect to the one found in circular motion, exists in rectilinear uniform motion. We conclude that the circular Sagnac effect is fully explainable in the framework of inertial systems, and that the circular Sagnac effect contradicts special relativity theory and calls for its refutation.

Miniaturized and low-cost optical gyroscopes are urgently required for emerging applications in consumer electronics market. In this paper, we proposed a theoretical analysis and preliminary experiment results for integrated interferometric optical gyroscope based on the silicon-on-insulator (SOI) platform for the first time. The gyroscope is based on the Sagnac effect and composed of coiled multimode waveguides to reduce propagation loss and the footprint. The sensitivity of the sensing part is fully investigated in terms of waveguide loss, gyroscope footprint, crossing numbers for coiled waveguides, as well as the waveguide cross section. The experimental results show that gyroscope sensitivity is 51.3 deg/s with a footprint of 600 μm × 700 μm.

We investigate the Sagnac effect in the self-interference add–drop resonator (SIADR), and propose a rotation sensing frame based on the SIADR. The Sagnac effect in an SIADR can be equivalent to that in a two-resonator structure without the detuning between the two resonators. Two optical waves are spontaneously formed in the SIADR, and their interference signal carries the information of angular velocity. Distinguishing the direction of angular velocity can be achieved by setting asymmetrical coupling coefficients in the SIADR. We also show the rotation sensing experimental results in the SIADR made of single mode fiber, which are in good agreement with the theoretical results. The results may open new avenues for rotation sensing.

Anomalous dispersion enhancement physical mechanism for Sagnac effect is described by special relativity derivation, and three kinds of definitions of minimum detectable angular rate of resonance optical gyroscope (ROG) are compared and the relations among them are investigated. The effect of linewidth broadening induced by anomalous dispersion on the sensitivity of ROG is discussed in this paper. Material dispersion-broadened resonance linewidth deteriorates the performance of a passive ROG and dispersion enhancement effect, while the sensitivity of a structural dispersion ROG is enhanced by two orders of magnitude even considering the dispersion-broadened resonance linewidth.

We investigate the various macroscopic quantum coherences including one-, two- and three-mode ones in a spinning whispering-gallery-mode resonator system and examine how the input laser power, the coupling strength of the optical modes, the rotating angular velocity, and the optical and mechanical decay rates influence them. We find in two- and three-mode quantum coherences the one-mode quantum coherences play a main role. We also find that the quantum coherences in the spinning system are nonreciprocal, they monotonically increase as the rotating angular velocity increases when the driving direction of the laser field is consistent with the rotation direction of the resonator, otherwise they reduce monotonically.

The main factors that limit the performance of ring laser gyroscopes include random walk, quantization noise, and bias stability. The first two factors determine the alignment time for navigation systems, and the bias stability error can result in long-term accuracy. We show that a phase wrapping/unwrapping algorithm, which has been widely used in interferometry fields, can be utilized to remove lock-in and quantization errors by implementing a zero-lock-in ring laser gyroscope. Furthermore, the performance of the ring laser gyroscope with no mechanical dither is described, and mirror dithering, instead of mechanical dithering, is proposed.

International audience; The French physicist Georges Sagnac is nowdays frequently cited by the engineers who work on devices such as ring-laser gyroscopes. These systems operate on the principle of the Sagnac effect. It is less known that Sagnac was a strong opponent to the theory of special relativity proposed by Albert Einstein. He set up his experiment to prove the existence of the aether discarded by Einsteinian relativity. An accurate explanation of the phenomenon was provided by Paul Langevin in 1921.; Le nom de Georges Sagnac est aujourd'hui très connu des ingénieurs travaillant sur les systèmes de navigation, tant maritime qu'aérienne, qui exploitent sa découverte de 1913. Ce que l'on sait moins est que ce physi-cienétait un farouche opposantà la relativité, théorie révolutionnaire qui avaitétéélaborée par Albert Einstein quelques années auparavant en 1905. L'expérience de Sagnac aété pensée pour prouver l'existence de l'éther lu-minifère. Son interprétation correcte (relativiste) aété fournie par Paul Langevin en 1921.

Waveguide ring resonator (WRR) is beneficial to the miniaturization and integration of the resonant micro optic gyroscope (RMOG). The shot-noise-limited sensitivity of the RMOG equipped with the multi-turn WRR is derived. The simulation results show that when the crossing loss or the waveguide propagation loss is higher than 0.07 dB/crossing or 1.2 dB/m, the WRR of multi-turn structure does no good to the sensitivity of the RMOG. Two configurations of the WRR are introduced and tested. According to the measured waveguide propagation loss and crossing loss, the optimal angular random walk (ARW) is obtained when the RMOG equipped with a WRR of 2 or 3 turns. The ARW of the RMOG equipped with a 3-turn WRR is measured at different laser output power which agrees well with the theoretical value.

This paper proposes a complementary frequency electromagnetic gyroscope. In this gyroscope, a voltage-controlled oscillator (VCO) is applied to generate complementary frequency signals and the angular rate detection is realized based on a phase-locked loop. The complementary frequency electromagnetic gyroscope can be fully realized by micro-electronic technology, which is beneficial to the miniaturization of the angular rate measurement system and has a wide application prospect. The complementary frequency electromagnetic gyroscope extends the application of the Sagnac effect and replaces the optical signal with the electromagnetic pulse signal. It can make full use of the advantages of microelectronic technology and microwave technology to realize the miniaturization of measuring components and even realize the system on a chip. In this paper, the mathematical model of the complementary frequency electromagnetic gyroscope is established and verified by simulation analysis. Theoretical analysis shows that the measured angular rate is proportional to the relative frequency difference of complementary VCO output. The simulation results indicate that the sensitivity of the complementary frequency gyroscope is 1 × 10−5 rad/s and is insensitive to noise. When the signal-to-noise ratio is lower than 0 dB, the gyroscope still has good angular rate measurement accuracy.

In this paper, the uncertainty of time transfer based on a bidirectional time division multiplexing transmission over a single fiber with the same wavelength (BTDM-SFSW) is investigated via theoretical models and experimental measurements. According to the principle and system architecture, the uncertainty evaluation schemes for BTDM-SFSW based time transfer are presented and the uncertainty sources are identified accordingly. In order to avoid the effect of the temperature-dependent fiber delay, the measured time intervals at two sites are regarded as a whole to obtain an overall uncertainty of time interval measurements. For the uncertainty of time transfer modem calibration, aside from the type A uncertainty obtained under the applied calibration scheme, the system reproducibility against practical operation and the contribution of optical power-dependent receiving delays are also included. A mathematical model considering fiber dispersion, polarization mode dispersion (PMD) and the Sagnac effect is established to evaluate the uncertainty from the fiber link. The characteristics of the uncertainty sources in a long-distance fiber-optic time transfer testbed are then explored in detail. The combined expanded uncertainties with a coverage factor of 2 are calculated and experimentally validated over various non-calibrated fiber extensions.