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The impact of light scalars coupled conformally and disformally to matter on the geodetic and frame-dragging (FD) precessions is calculated. For larger frequencies the disformal interaction becomes increasingly relevant. We use several satellite experiments and Pulsar time of arrival (ToA) measurements to derive bounds on the couplings, combining the Gravity Probe B, LARES, LAGEOS and GRACE results with pulsar timings. Forecasts for future constraints on the conformal and the disformal couplings based on the GINGER experiment, i.e. a future measurement of the Sagnac effect on Earth, the motion of $S$-stars around the galactic centre and future pulsar timing observations are presented., Comment: 14 pages

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.

We consider an example of a moving closed contour and the role played by simultaneity in the description of light propagation on the contour's moving sections. We show that, when constrained to propagate along the contour, the local speed of light on a moving section is no longer arbitrary and a consistent description requires conservation of simultaneity.

The Sagnac effect and related twin paradox with a rotating disc are analyzed. It may seem that the special theory of relativity gives an easy and exhaustive treatment here. However, such consideration is deceptive since the principles of special relativity are originally established only for the inertial frames of reference, whereas the Sagnac experiment and the twin paradox exist in a noninertial one. We introduce an additional group of motions related to the rotation with uniform angular speed and show that these transformations leave the Minkowski metric invariant. Thus, we can give a firm mathematical ground to a usual easy consideration of the Sagnac effect. It should be noted that the presented result is true for a special case of motions; general coordinate transformations into accelerating frames of reference do not preserve the metric.

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.

This paper investigates one of the most interesting effects associated with the rotation of astrophysical objects (the Sagnac effect). The effect was first confirmed in laboratory experiments by Georges Sagnac with a rotating ring interferometer in 1913. Later, the effect was also confirmed within the framework of the Earth in the "Around-the-World" experiment conducted by J. Hafele and R. Kitting, in which they twice circled the Earth with an atomic cesium clock on board and compared the "flying" clock with those remaining static on the Earth. As a result, a non-zero difference in the clock rate was found as a confirmation of the Sagnac effect. Subsequently, more precise satellite experiments have been carried out to measure the Sagnac effect within the Earth. The effect was also considered in general relativity and modified theories of gravity, where many works were carried out to study the influence of such parameters as angular momentum, cosmological constant, Ricci scalar, etc. on the Sagnac effect. An interesting task is to study the influence of a magnetic charge on the effect, since the solution with rotation described by a black hole with mass M and magnetic charge g is the Bardeen nonsingular black hole. The work will calculate the Sagnac effect in the space-time of the rotating Bardeen black hole for both geodesic and non-geodesic circular orbits of the light source / receiver (assuming that the light source and receiver are defined at the same point). Two types of circular orbits describe the opposing influence on the Sagnac effect: the Sagnac delay increases with an increase in the magnetic charge in the case of non-geodesic circular orbits and decreases in the case of geodesic circular orbits. However, the farther is the orbit of the light source / receiver, the less the magnetic charge affects the Sagnac delay. It is also assumed that the gravity of the Earth and the Sun near the surface is well described by the Bardeen metric.

In this study, the impact of non-inertial effects, caused by rotational motion, on the cylindrical perfect cloak is simulated. Also, the interactions between plane waves, Gaussian sine, and Gaussian pulse are investigated. it is shown that non-inertial perfect cloak could be detectable with the Sagnac and magnetoelectric effects.at low frequency of gyration, the distortion of waveform pattern is humble and negligible, however when the rotational frequency increases, the pattern distortion becomes huge and wavelets are formed and their intensity grows up. the scattering pattern can be influenced by the direction of rotation, thus, the direction of rotation could be identified with the scattering pattern analysis. Also, a method for measuring rotational velocity can be prepared concerning the electric field phase retardation. the simulation is computed using the FDTD methods by transforming the Maxwell's equations from non-inertial frameworks to the lab framework., Comment: 14 pages, 10 figures

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.

A rotating solid homogeneous isotropic dispersion-free dielectric in an accompanying frame of reference turns out to be an inhomogeneous anisotropic medium due to the action of two competitive physical mechanisms: inhomogeneity of the free space caused by rotation and light dragging by the moving medium. In the rotating dielectric, the eikonal equation and a system of ordinary differential equations corresponding to it in the characteristic form are obtained in the geometrical optics approximation. Solutions of the equations at calculated parameters determined using first integrals of the system are pairs of counterpropagating R-trajectories of rays and f-trajectories of phase fronts. A formula for the intensity of a light pulse propagating along an arbitrary R-trajectory is obtained. Counterpropagating trajectories of both types have no common points and are shifted to the opposite sides from the straight line between the end points. Their structural parameters (the minimum distance to the axis of rotation, arc length, domain with respect to the azimuthal coordinate, optical length, etc.) vary under the action of both physical mechanisms depending on the rotation velocity. Closed optical paths in the rotating reference frame (RRF) for a retransmitting network and for a two-mirror Fabry–Perot resonator in an operating laser can be created using two types of mirrors adapted to the rotation frequency; the normals to the reflecting surfaces of the mirrors must have definite different angles with unit vectors of rays and wavefronts of the radiation arriving at the reflector. The Sagnac effect is a consequence of inhomogeneity (deformation) of the free space with respect to the azimuthal coordinate and its magnitude is the result of the competitive action of both physical mechanisms.

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.

Background and Objectives: In the present paper the physical backgrounds of three types of microwave gyroscopes are presented. Materials and Methods: Using the relativistic approach the relations for output characteristics are derived to determine the main parameters and properties of the microwave gyro devices: voltage tuned magnetron (mitron) and microwave gyros based on the resonant cavity, and for microwave gyro with coil. Results and Conclusion: The results can be used to determine the main parameters of these devices and their properties. The calculated parameters are compared with the parameters and properties of Laser Gyros, Fiber Optics Gyros and with other types of gyros. The discussion of their realizations issues and subsequent applications at the moving objects is given.

We investigate rigorously the behaviour of light propagation in the closed contour of the linear Sagnac effect. Assuming that the local light speed is c in a section of the contour, our approach ma...

The geometry of the Sagnac effect in a stationary region of a spacetime is reviewed with the aim of emphasizing the role of asymmetry of a Finsler metric defined on a spacelike hypersurface associated to a stationary splitting and related to future-pointing null geodesics of the spacetime. We show also that an analogous asymmetry comes into play in the Sagnac effect for timelike geodesics., Comment: AMSLaTeX, 6 pages; v3: a misprint in Eq. (3) and in the equation at the end of the paper corrected; these two corrections are not included in the published version

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.

In this paper, analysis of tunable optical filter based on Sagnac effect tuning is presented using a fiber-optic ring resonator (FORR) and the responses of the filters for different FORR and Sagnac loop parameters under steady-state conditions are investigated. Formulation of the optical filter response is presented by considering with/without single and multiple Sagnac loop effects. Effects of the FORR parameters of filter response are studied and analyzed under different parametric conditions for the maximum transmission intensity. The simulation results show that the filter responses are affected strongly by the Sagnac loop and the FORR parameters. With the Sagnac effect, it is shown that full-width at half maximum (FWHM) would increase by increasing the phase difference Δϕ from 0 to 0.20 radian, beyond which it will start decreasing. The difference in FWHM value in this range of Δϕ variations is found to be about 3.77 nm. Between the first and the second resonances at wavelengths 1395 and 1538 nm, the free spectral range (FSR) is found to be 140 nm. In multiple loops effects, by increasing the number of loop turn N, the values of FSR would reduce. For Δϕ = 0.3 and N = 1, 2, 3, the values of FSR are obtained as 144, 74, 47 nm, respectively.

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.

We put forward a new fiber optic sensor for measuring linear velocity with picometer/second sensitivity with Weak-value amplification based on generalized Sagnac effect [Phys. Rev. Lett.\textbf{93}, 143901(2004)].The generalized Sagnac effect was first introduced by Yao et al, which included the Sagnac effect of rotation as a special case and suggested a new fiber optic sensor for measuring linear motion with nanoscale sensitivity. By using a different scheme to perform the Sagnac interferometer with the probe in momentum space, we have demonstrated the new weak measure protocol to detect the linear velocity by amplifying the phase shift of the generalized Sagnac effect. Given the maximum incident intensity of the initial spectrum, the detection limit of the intensity of the spectrometer, we can theoretically give the appropriate pre-selection, post-selection, and other optical structures before the experiment. Our numerical results show our scheme with Weak-value amplification is effective and feasible to detect linear velocity with picometer/second sensitivity which is three orders of magnitude smaller than the result $\nu$=4.8 $\times$ $10^{-9}$ m/s obtained by generalized Sagnac effect with same fiber length., Comment: 3 figures; 9 pages. arXiv admin note: substantial text overlap with arXiv:2105.13638

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.

The principle of the constancy of the velocity of light, which stated that the light velocity is invariant to the motion of the emitter, was well established and directly proven by many experiments. Interestingly, the further assumption that the light velocity is also independent of the motion of the observer was, arguably, never conclusively proven by any experiment for a century. This paper tried to address some perceived technical difficulties in such experiments and proposed two experiments to test this assumption. One is to directly measure the light speed as to moving sensors, with the setup designed in such a way that the concerns of time synchronization and dilation can be avoided. Another experiment is to test the isotropy of the light speed to a high-speed particle by measuring the momentum to acceleration ratio. The experiment results, if positive, will provide direct proof of the assumption. Otherwise, it may imply a need for further investigation. Since the light speed invariance to moving observers is a key assumption of some fundamental physical theory, either way, the experiments will have significant importance.

We report the GPS satellite clock estimation using 20 globally distributed receivers with an external hydrogen maser atomic clock. By applying corrections for the Sagnac effect, the relativistic effect due to orbit eccentricity, tropospheric and ionospheric delays, satellite and receiver antenna phase center offsets and variations, solid earth tides, ocean tide loading, phase wind-up effect, and P1-C1 bias, our satellite clock results matches the IGS final clock product within ± 1.4 ns with comparable frequency stability for an averaging time of less than 1000 sec and a 10–30% worse frequency stability for an averaging time of greater than 1000 sec, on MJD 58244. This small atomic clock network results in a fast computation that becomes increasingly appealing when the real-time satellite orbit and clock estimation is needed and as the GNSS constellations and the GNSS signals expand.

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.

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.

We consider a thought experiment, equivalent to the Sagnac effect, where a light signal performs a round trip over a closed path. If special relativity (SR) adopts Einstein synchronization, the result of the experiment shows that the local light speed cannot be c in every section of the closed path. No inconsistencies are found when adopting absolute synchronization. Since Einstein and absolute synchronizations can be discriminated, the conventionality of the one-way speed of light holds no longer. Thus, as sustained by specialists, it might be a viable formulation of SR that reinstates the conservation of simultaneity, even though it allows for relativistic effects, such as time dilation. Such an approach may lead to the discovery of new effects and a better understanding of relativistic theories.

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.

A world system is composed of the world lines of the rest observers in the system. We present a relativistic coordinate transformation, termed the transformation under constant light speed with the same angle (TCL-SA), between a rotating world system and the isotropic system. In TCL-SA, the constancy of the two-way speed of light holds, and the angles of rotation before and after the transformation are the same. Additionally a transformation for inertial world systems is derived from it through the limit operation of circular motion to linear motion. The generalized Sagnac effect involves linear motion, as well as circular motion. We deal with the generalized effect via TCL-SA and via the framework of Mansouri and Sexl (MS), analyzing the speeds of light. Their analysis results correspond to each other and are in agreement with the experimental results. Within the framework of special and general relativity (SGR), traditionally the Sagnac effect has been dealt with by using the Galilean transformation (GT) in cylindrical coordinates together with the invariant line element. Applying the same traditional methods to an inertial frame in place of the rotating one, we show that the speed of light with respect to proper time is anisotropic in the inertial frame, even if the Lorentz transformation, instead of GT, is employed. The local speeds of light obtained via the traditional methods within SGR correspond to those derived from TCL-SA and from the MS framework.

General relativity predicts the presence of a gravito-magnetic component of the gravitational interaction induced by a rotating mass. It is currently assumed that our galaxy (as well as the others) is immersed in a dark halo. If so, it is reasonable to expect the halo to rotate, then to produce a gravito-magnetic field. Here we present a proposal to measure such effect exploiting the fully relativistic version of the Sagnac effect. When an electromagnetic signal is led to travel along a spacely closed path immersed in a gravito-magnetic field the time of flight for a complete turn depends on the direction of rotation. The proposed physical loop would be based on the Lagrange points of the Sun-Earth pair. An evaluation of the sensitivity of such a measurement, together with a discussion of more opportunities that the experiment would offer is also presented.

A coupling effect in the single-mode fiber coil (SMFC) of a depolarized interference fiber optic gyroscope (De-IFOG) under time-varying temperature and magnetic field, which can cause a serious nonreciprocal phase error, is revealed. In this paper, the mechanism of the coupling effect is thoroughly studied and the related theory is derived in detail. Simulations and experiments are carried out to verify the validity. The experiments show a peak-to-peak value error of about 50 °/h in the SMFC when the magnitude of magnetic field is 10 Gauss and the temperature uniformly increases from 10 to 60 °C at the rate of 36 °C/h, which cannot be neglected in the applications of De-IFOGs.

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.

Ring Laser Gyroscopes (RLG) are widely used in Inertial Navigational Systems for detection of body rotation. But the performance is limited by lock- in state of RLG. To avoid this problem the Laser cavity of RLG is mechanically dithered. This process ensures that RLG stays out of the lock- in zone during its operating condition. But the dither signal appears as noise, which must be removed to obtain the true rotation of the body. This can be achieved by the use of digital filters. The required digital filter should have very high attenuation in the dither band and linear phase response in the pass band. Two types of multistage digital filters namely BBB and BCO filters are developed to remove the dither signal to an acceptable level. The BCO combined filter is found to be good and the same filter is implemented in real time using FPGA. The simulated results and the real time results are compared and found to be nearly same in both cases.

More than a century ago, M. Sagnac realized an experiment with light rays, whose results according to him invalidated the theory of Relativity and validated the hypothesis of the Aether. This hypothesis of the ether was not retained by the scientific community, and relativistic explanations were given to the results of the Sagnac experiment. But these relativistic explanations remain open to criticism because they are various and because the prediction may differ depending on whether the observer’s frame of reference is at rest or in motion. The neo-Newtonian mechanics proposes a new explanation which leads to demonstrate the formula with P the light path. In order to verify this new interpretation, it is proposed to do again the Sagnac experiment with a slightly different light path, a square-shaped path. The results should be at least 30% lower than those predicted by the theory of Relativity. In which case, the relativistic explanation would be questioned.

In this paper, we investigated the concept of the Sagnac effect in passive integrated optical gyroscope base photonic crystal ring resonator for angular velocity sensing. This configuration utilizes one 3 dB coupler, two Bus waveguides, and five ring resonators for rotation sensing. The structure has been designed using dielectric silicon rods which are embedded in air. The transmission efficiency of the photonic crystal ring resonator at 1551 nm is about 96% with quality factor and bandwidth values equal to 4326 and 0.35 nm, respectively. By measuring the power of the output port, it is possible to estimate the phase shift and then to measure the rotation rate. The central wavelength of structure is assumed to be equal to 1569.9 nm. The structure characteristics have been investigated by using the two-dimensional finite-difference time-domain method. The footprint of the structure is approximately 279 μm2.

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.

A resonant fiber optic gyro (RFOG) is a high-accuracy inertial rotation sensor based on the Sagnac effect. Knowledge of the laser frequency noise, especially the study of its transfer characteristics is critical to optimize the resonant frequency servo loop parameters in the RFOG. In this paper, a Mach–Zehnder interferometer (MZI) is used to measure the changes of the power spectral density (PSD) of the laser frequency noise. Three different observation points are set to investigate the transfer characteristics of the laser beam along the transmission loop of the RFOG. Through real-time observation and analysis of the PSDs of the laser frequency noise, we found that the effects of the laser frequency noise on the RFOG can be clearly determined, and the resonant frequency servo loop parameters can be optimized according to the required gyro bandwidth. We also demonstrate the significance of reducing the residual error at the lock-in frequency while ensuring a sufficient gyro bandwidth.

In seismology, an increased effort to observe all 12 degrees of freedom of seismic ground motion by complementing translational ground motion observations with measurements of strain and rotational motions could be witnessed in recent decades, aiming at an enhanced probing and understanding of Earth and other planetary bodies. The evolution of optical instrumentation, in particular large-scale ring laser installations, such as G-ring and ROMY (ROtational Motion in seismologY), and their geoscientific application have contributed significantly to the emergence of this scientific field. The currently most advanced, large-scale ring laser array is ROMY, which is unprecedented in scale and design. As a heterolithic structure, ROMY’s ring laser components are subject to optical frequency drifts. Such Sagnac interferometers require new considerations and approaches concerning data acquisition, processing and quality assessment, compared to conventional, mechanical instrumentation. We present an automated approach to assess the data quality and the performance of a ring laser, based on characteristics of the interferometric Sagnac signal. The developed scheme is applied to ROMY data to detect compromised operation states and assign quality flags. When ROMY’s database becomes publicly accessible, this assessment will be employed to provide a quality control feature for data requests.

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.

We study the amplification of rotation velocity with the Sagnac interferometer based on the concept of weak-value amplification. By using a different scheme to perform the Sagnac interferometer with the probe in momentum space, we have demonstrated the new weak measure protocol to detect the small rotation velocity by amplifying the phase shift of the Sagnac effect. At the given the maximum incident intensity of the initial spectrum, the detection limit of the intensity of the spectrometer and the accuracy of angular velocity measurement, we can theoretical give the appropriate potselection and the minimum of optical path area before experiment. In addition, we put forward a new optical design to increase the optical path area and decrease the size of the interferometer to overcome the limit of instrument size. Finally, our modified Sagnac's interferometer based on weak measurement is innovative and efficient probing the small rotation velocity signal., Comment: arXiv admin note: text overlap with arXiv:1203.0827 by other authors

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

The physical principles of a chip-based Brillouin laser gyroscope are reviewed. The device can resolve sinusoidal rotations with amplitude as low as 5 degrees/hour and is also used to detect the Earth’s rotation.

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.

We theoretically study optomechanically induced second-order sideband generation in a spinning resonator. Due to the splitting of resonance frequencies of the countercirculating modes via the Sagnac effect, we find that second-order sidebands can be enhanced in one direction but suppressed in the other. Furthermore, the enhancement or suppression of second-order sidebands is closely related to the rotation speed of a resonator, incident direction of input fields, and frequency of driving fields. Finally, we study the influence of power of control fields on second-order sidebands, and find that the operating bandwidth for observing an obvious nonreciprocal enhancement of second-order sidebands can be significantly widened as the power of control fields increases. Our paper offers a promising route towards achieving tunable optical nonlinearity and convenient nonreciprocal optomechanical control in integrated photonic chips.

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.

The original version of this article containes a mistake. In the second line of Comment 2, it should read: “It is necessary to note that Schwarzschild metric is static while the rotating metric (which is the subject of discussion) is stationary.”