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The performance of color matching functions (CMFs) is important to color specification and calibration. In comparison to the great number of studies focusing on the effect of primary set, few studies focused on how observer age and field of view (FOV) jointly affected the performance of CMFs. In this study, a color matching experiment with three different primary sets, which were carefully selected based on our previous study, was carried out by two observer age groups under four FOVs (i.e., 2°, 4°, 8°, and 13°). The results suggested that the observer age had a more significant effect than the FOV, and the change of the FOV did not introduce a systematic trend to the color matching results. Neither the CIE 1931 2° nor 1964 10° CMFs were found to accurately characterize the color matches. The CIE 2006 CMFs with the FOV set to the experiment setup also did not have good performance. On average, the CIE 2006 2° CMFs were found to have the best performance, without considering the effects of the observer age and FOV. [ABSTRACT FROM AUTHOR]

In this article, the design and simulation of an optical gyroscope based on a hybrid ring resonator using the Sagnac effect are presented. In this design, by using a transfer matrix, numerical analysis, and tight-binding methods, as well as managing control factors in the sensor, such as the transfer coefficient, ring radius of each resonator, operating wavelength, and coupling coefficient, the sensor output parameters are investigated. The output parameters include sensitivity, angular random walk (ARW), minimum angular rotation, minimum group velocity, and the phase shift resulting from the power ratio changes. In this gyroscope, the maximum group velocity in terms of angular rotation with the increase of the number of rings is an exponential function in the range of 750–2500 m/s. The output phase changes as a linear function with an upward slope as the radius of the rigs increases in the range of 2130–3430 nm. Also, with the increase in the radius of the rings, the phase change relative to the operating wavelength decreases. By increasing the imaginary part of the coupling and transfer coefficients in this sensor, the changes in output power decrease compared to the output phase. The transmission peaks in the gyroscope output increase due to the rise in the number of rings. The sensitivity lowers with an increasing number of rings. The temperature affects the gyroscope output, and an increase in temperature causes a rise in ARW and a decrease in the signal-to-noise ratio. Also, the signal-to-noise ratio increases with the rise of the output power due to the transfer and coupling coefficients. [ABSTRACT FROM AUTHOR]

Abstract The result of the Michelson-Gale experiment, which shows fringe shifts by the interference between two light beams traversing a rectangular loop in opposite directions, has been nonrelativistically analyzed based on the Galilean transformation. We relativistically analyze it via the transformation under the constant light speed (TCL) and via the framework of Mansouri and Sexl (MS). The TCL provides a coordinate transformation between the isotropic frame and a rotating frame, in which the two-way speed of light is a constant c irrespective of direction on the surface that has the same radius of rotation. When using TCL, we assume that the Solar System is isotropic so that the one-way speed of light is c in it. On the contrary, considering its movement, the analysis is carried out without the assumption of isotropy based on the MS framework. The analysis results via the TCL and via the MS framework correspond to each other and are in agreement with the result of the experiment. It is shown that the difference between the travel times of the counter-propagating light beams, which results in the fringe shift, takes place due to the two factors, the anisotropy of the one-way speed of light in inertial frames and the different rotation radii at different latitudes on the Earth surface.

The GINGER (gyroscopes in general relativity) project foresees the construction of an array of large frame ring laser gyroscopes, rigidly connected to the Earth. Large frame ring laser gyroscopes are high-sensitivity instruments used to measure angular velocity with respect to the local inertial frame. In particular, they can provide sub-daily variations in the Earth rotation rate, a measurement relevant for geodesy and for fundamental physics at the same time. Sensitivity is the key point in determining the relevance of this instrument for fundamental science. The most recent progress in sensitivity evaluation, obtained on a ring laser prototype, indicates that GINGER should reach the level of 1 part in 1011 of the Earth’s rotation rate. The impact on fundamental physics of this kind of apparatus is reviewed.

The result of the Michelson-Gale experiment, which shows fringe shifts by the interference between two light beams traversing a rectangular loop in opposite directions, has been nonrelativistically analyzed based on the Galilean transformation. We relativistically analyze it via the transformation under the constant light speed (TCL) and via the framework of Mansouri and Sexl (MS). The TCL provides a coordinate transformation between the isotropic frame and a rotating frame, in which the two-way speed of light is a constant c irrespective of direction on the surface that has the same radius of rotation. When using TCL, we assume that the Solar System is isotropic so that the one-way speed of light is c in it. On the contrary, considering its movement, the analysis is carried out without the assumption of isotropy based on the MS framework. The analysis results via the TCL and via the MS framework correspond to each other and are in agreement with the result of the experiment. It is shown that the difference between the travel times of the counter-propagating light beams, which results in the fringe shift, takes place due to the two factors, the anisotropy of the one-way speed of light in inertial frames and the different rotation radii at different latitudes on the Earth surface. [ABSTRACT FROM AUTHOR]

The main goal of the article is to present the concept of using a simulation environment when designing an advanced fibre-optic seismometer (FOS) using a field-programmable gate array (FPGA) computing system. The first part of the article presents the advanced requirements regarding the FOS principle of operation, as well as the measurement method using a closedloop operation. The closed-loop control algorithm is developed using the high-level language C++ and then it is synthesised into an FPGA. The following part of the article describes the simulation environment developed to test the operation of the control algorithm. The environment includes a model of components of the measurement system, delays, and distortions in the signal processing path, and some of the measurement system surroundings. The article ends with a comparison of simulation data with measurements. The obtained results are consistent and prove correctness of the methodology adopted by the authors. [ABSTRACT FROM AUTHOR]

Harmonia axyridis (H. axyridis) is the natural enemy of many aphid species. Traditional manual release of H. axyridis adults requires substantial manpower, and release efficiency is low. Automatic mechanical devices can improve the efficiency of delivery. Based on H. axyridis adults' morphological size, a prototype release system for H. axyridis was designed, which considered the adhesion characteristics of H. axyridis adults. According to the measured physical characteristics of H. axyridis adults, the structural parameters of the mechanical system for the release of the H. axyridis adults were determined. The relationship of the quantity of release, the impeller rotating speed, and the time for the release of H. axyridis adults were constructed. The mechanism can quantitatively adjust the number of H. axyridis adults to meet a certain H. axyridis-aphids ratio. Combining the image processing technology with the camera function of a mobile phone, the maximum cross-sectional area method was used to count the H. axyridis adults in the designated area. Results showed that the impeller rotating speed had a significant effect on the survival rate of the H. axyridis adults. When the airflow velocities were 29.5 m/s and 38.3 m/s, the survival rates of the H. axyridis adults were 93.8% and 94.5% at 4.2 rpm. The adhesion rate of the H. axyridis adults was 2.5%-4.6%. This work will provide technical support for the research of biological control. [ABSTRACT FROM AUTHOR]

Immersion microscope objectives stand out for their large numerical aperture, which improves the optical resolution of imaging systems such as those used in microscopic interferometry. These objectives increase the gradient forces of a beam focused through them, forming an Optical Trap (OT). However, many studies on microscopic interferometry neglect the contributions of different optical materials in the system that are also exposed to laser radiation, perhaps simply assuming transparency. In this work, a Mach–Zehnder interferometer and an OT, which share several components (including the same oil immersion objective), were coupled. Here, the response of the interferometer to a progressive increase in the OT laser power, while the interferometer laser power remains constant, is reported. Changes in laser power affect the oil temperature, altering its refractive index and volume, which in turn causes a phase shifting on the transmitted wavefront. Optical phase analysis is applied in the three-dimensional measurement of the damage produced by the OT on a paint film. This study suggests that the refractive index variations in the immersion oil affect interferograms because they will then exhibit an additive phase term that must be considered in that final measurement. Additionally, the OT geometry changes with the power increase. [ABSTRACT FROM AUTHOR]

Ring Laser Gyroscopes, based on the Sagnac effect, are currently the most sensitive rotation sensors. GINGERINO, a RLG installed underground, shows a proved sensitivity that enters the few frad/s regime in about 2.5 days of integration time. On one hand, this sensitivity is well below the shot--noise--level as predicted applying to GINGERINO the so called independent beam model. On the other hand, it paves the way to the use of RLG in fundamental and quantum physics research. Indeed, high sensitivity rotation measurement opens to test general relativity and alternative theory of gravity. Moreover, it make possible to study the interplay between quantum effects in the optical domain and non-inertial reference frames. [ABSTRACT FROM AUTHOR]

Phase shift plays a vital role in the analysis of interference and manipulation of polarization behavior in interferometric techniques. The Sagnac interferometer (SI) is initially studied due to its ability to withstand external environmental factors, including noise, temperature, and other interferences. However, the real impact of these factors is not demonstrated. To address this, comparative studies are conducted involving both mathematical theories, simulations, and physical experiments of Sagnac and Mach-Zehnder interferometers (MZI), both utilizing a phase shift. The purpose is to explore the SI advantages over the MZI in a series of experiments with both interferometers to validate the superior configuration. Numerical simulations of the total electric field are performed at the output of these interferometers. By adjusting the orientation of a half-wave plate from 45 and 135 degrees at a step of 90 degrees, the interference fringe pattern and respective signal are generated. These simulation parameters are then implemented experimentally, and the results from both approaches are carefully analyzed and compared. It is shown that the light reflection through the SI setup makes it more tolerant to noise compared to the MZI. Consequently, these results confirm that the image intensity and pixel level of the SI are higher than that of the MZI, potentially leading to greater brightness for the simplified image analysis. [ABSTRACT FROM AUTHOR]

High-precision Time-Frequency Rack (HTFR) mission, a part of experiment module II of the China Space Station (CSS), was equipped with a Sr optical clock, H-maser, and laser-cooled microwave clock. To compare time and frequency across widely separated clocks, a microwave link, and a pulsed laser link were both established, which probably enables new possibilities for fundamental science, geodesy, and metrology. Based on the existing relativistic theory for time and frequency transfer, we derive a relativistic model of satellite-ground laser time transfer on CSS (CLT), which can be of direct use in CLT data processing. In addition to first and second-order Sagnac effects, it also includes relativistic rate shifts, atmospheric refraction, and turbulence, laser retroreflector array (LRA) range correction, and position correction between detector and reflector, satisfying the stability evaluation of CSS atomic clocks with fractional frequency stability of 3 × 10−17/10000 s. Additionally, we numerically investigate the link error magnitude and use Monte Carlo simulations to assess the impact of correcting for link errors on the stability of the CLT, taking into account the CSS orbit and attitude determinations as well as the CLT payload calibration parameters. It is shown that the CLT link can be considered to reach a TDEV of approximately 0.1 ps/300 s while meeting the CSS design objectives. The primary factors that influence the stability of the CLT are the position correction between detector and reflector, LRA range correction, and the coupling relation of these two error distributions. [ABSTRACT FROM AUTHOR]

The GINGER (gyroscopes in general relativity) project foresees the construction of an array of large frame ring laser gyroscopes, rigidly connected to the Earth. Large frame ring laser gyroscopes are high-sensitivity instruments used to measure angular velocity with respect to the local inertial frame. In particular, they can provide sub-daily variations in the Earth rotation rate, a measurement relevant for geodesy and for fundamental physics at the same time. Sensitivity is the key point in determining the relevance of this instrument for fundamental science. The most recent progress in sensitivity evaluation, obtained on a ring laser prototype, indicates that GINGER should reach the level of 1 part in 10 11 of the Earth's rotation rate. The impact on fundamental physics of this kind of apparatus is reviewed. [ABSTRACT FROM AUTHOR]

For the first time, electromagnetic wave interaction with a perfect non-inertial cloak is investigated. The electromagnetic detection of an ideal gyrating cloak, the effect of rotational speed on the scattering pattern, and the determination of rotational direction and rotational velocity magnitude are investigated in the present paper. It is shown that a rotating cloak is electromagnetically detectable due to the magneto-electric and Sagnac effects. These phenomena create bending in the passing wave pattern and generate cylindrical wavelets that are observable in the electromagnetic scattering pattern. It is shown, the gyrating cloak's speed and direction can be determined using the amplitude of wavelets and bending location in the pulses passed because they increase with growing angular frequency. At low frequency gyration, the distortion of waveform pattern is humble and negligible; however, when the rotational frequency increases, the pattern distortion becomes huge, wavelets are formed, and their intensity grows. The direction of rotation can influence the scattering pattern; thus, the rotation direction could be identified with the scattering pattern analysis. The simulation is computed using the FDTD method by transforming Maxwell's equations from the non-inertial framework to the lab framework. [ABSTRACT FROM AUTHOR]

Voltage-related power quality issues, including voltage sag, swell, and total harmonic distortion (THD), have become a significant concern in recent times. These issues, particularly harmonics, are known to degrade utility performance and lifespan, necessitating urgent rectification to ensure a high-quality power supply. This is crucial as our generation increasingly depends on electricity for enhanced living standards. Flexible AC transmission system (FACTS) devices are gaining considerable interest as effective solutions to these problems. Among these, the dynamic voltage restorer (DVR) is particularly noteworthy for its potential to reduce power quality disturbances in the distribution network. In this study, we developed a DVR based on an artificial neural network (ANN) controller. The activation function employed was Train LM for the input and hidden layers, and pure linear for the output layer, with the Levenberg Marquardt back propagation (LMBP) serving as the training algorithm. The designed model was then tested to tackle voltage-related power quality problems in the distribution network of Jamal Din Wala (JDW) sugar mills. The comprehensive model featured a three-phase voltage source inverter, a scheme utilizing rotating reference frame theory, and sine pulse width modulation (SPWM) for voltage sag and swell sensing along with insulated gate bipolar transistor (IGBT) switching. We analyzed three types of DVR output defects using MATLAB/Simulink and compared the results of the ANN controller with those of a conventional PI controller. The DVR output was modeled in MATLAB/Simulink for three types of defects and two degrees of voltage sag and swell. The results demonstrated that the DVR effectively mitigated voltage sags and swells in the JDW sugar mills distribution network. Furthermore, during the validation of the proposed ANN, a comparison of results with the conventional PI controller under balanced and unbalanced sags and swells showed a significant improvement. The ANN achieved a voltage restoration of up to 99.8% and a total harmonic distortion of 13.5%, a marked improvement over the PI controller, which achieved 97% voltage restoration and 19.5% total harmonic distortion, respectively. [ABSTRACT FROM AUTHOR]

This work investigates the performance of dual and quad laser wavelengths at simultaneous angle adjustment of polarization controller based on a Sagnac loop mirror interferometer. From our observation, 13 m polarization maintaining fibers of PMF length performed better in terms of lasing lines, peak power and extinction ratio of 4, −8 dBm and 38 dB, respectively. When the intensity increases, the flatness and number of channels are improved to prove that significant power setting for the best laser performance. The flatness and number of lasers are changed with the simultaneous adjustment of half-wave plate and quarter-wave plate angles. These dual and quad laser wavelengths have good power stability according to the low fluctuation below 2.25 dB of peak power difference on the laser peaks within 100 minutes. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Large frame ring laser gyroscopes, based on the Sagnac effect, are top sensitivity instrumentation to measure angular velocity with respect to the fixed stars. GINGER (Gyroscopes IN GEneral Relativity) project foresees the construction of an array of three large dimension ring laser gyroscopes, rigidly connected to the Earth. GINGER has the potentiality to measure general relativity effects and Lorentz Violation in the gravity sector, once a sensitivity of 10 − 9 , or better, of the Earth rotation rate is obtained. Being attached to the Earth crust, the array will also provide useful data for geophysical investigation. For this purpose, it is at present under construction as part of the multi-components observatory called Underground Geophysics at Gran Sasso (UGSS). Sensitivity is the key point to determine the relevance of this instrument for fundamental science. The most recent progress in the sensitivity measurement, obtained on a ring laser prototype called GINGERINO, indicates that GINGER should reach the level of 1 part in 1011 of the Earth rotation rate. [ABSTRACT FROM AUTHOR]

The work is devoted to the study of the problem of using laser radiation in the supercontinuum mode in fiber optical gyroscopes. To achieve this goal, the following tasks were solved in the work. The physics of the process of measuring the angular velocity of an object based on the Sagnac effect is described. The factors influencing the resolution of the gyroscope are analyzed. These factors include fractional noise, unavoidable noise, and noise due to backscatter in the fiber, which can be minimized by using photonic crystal fibers and a broadband radiation source. It is proposed to use an optical supercontinuum (optical comb) as such a source. Thanks to its ultra-wide radiation spectrum, precision frequency reproduction accuracy, high radiation stability and femtosecond pulse duration, supercontinuum is considered as a promising radiation source in ranging, hyperspectral spectroscopy and imaging, tomography, and low-coherence white light interferometry. In the work of Lpischan, the physics of the supercontinuum generation process, its main characteristics. An analysis of the possibility of using an optical comb in optical gyroscopy has been carried out. Mathematical modeling of the influence of optical fiber characteristics and supercontinuum parameters on the sensitivity of a fiber gyroscope was carried out. The results of the work indicate the promise of further research on the creation of a photonic crystal fiber-optic gyroscope using supercontinuum laser radiation. [ABSTRACT FROM AUTHOR]

Sensor calibration is an important step in SLAM, and lightweight, inexpensive sensors are often used in Augmented Reality applications. The accuracy of sensor calibration directly affects the accuracy and reliability of subsequent image processing, recognition, perception, and positioning. The inertial processing unit is robust to the sudden motion effect, blurring appears in the middle of camera motion, and the overlap area between two frames is too small, so it is difficult to match feature points. The camera itself can solve the problem of IMU drift in the middle of slow motion, and the two are complementary. VI‐SLAM, which integrates vision and IMU, has become a hot research topic at present. In this paper, the INDEMIND calibration method is analyzed and improved, the maximum likelihood method is used to improve the calibration accuracy, and its effectiveness is verified in the experiment. [ABSTRACT FROM AUTHOR]

The “inertial mass” mi in the equation of motion to describe a carrier is usually m∗≠m0 where m0=9.1×10-31kg is the rest mass of an electron in free space. The aim of this paper is to study its “gravitational mass” mG and test the weak equivalence principle (WEP) mi=mG in condensed matter physics. First, the inertial forces in rotating systems are not 2miv×Ω and -miΩ̇×r. They should be 2mGv×Ω and -mGΩ̇×r. Secondly, we use the Sagnac effect and electromotive force (EMF) to determine the coefficient and compare with mi. Finally, the quantum energy levels caused by rotation are presented. The energies rely on the “gravitational mass”-to-“inertial mass” ratio mGmi=m0m∗≠1.

We present a dark fluid model described as a non-viscous, non-relativistic, rotating, and self-gravitating fluid. We assume that the system has spherical symmetry and that the matter can be described by the polytropic equation of state. The induced coupled nonlinear partial differential system of equations was solved using a self-similar time-dependent ansatz introduced by L. Sedov and G.I. Taylor. These kinds of solutions were successfully used to describe blast waves induced by an explosion following the Guderley–Landau–Stanyukovich problem. We show that the result of our quasi-analytic solutions are fully consistent with the Newtonian cosmological framework. We analyzed relevant quantities from the model, namely, the evolution of the Hubble parameter and the density parameter ratio, finding that our solutions can be applied to describe normal-to-dark energy on the cosmological scale. [ABSTRACT FROM AUTHOR]

We propose a method to map the conventional optical interferometry setup into quantum circuits. The unknown phase shift inside a Mach–Zehnder interferometer in the presence of photon loss is estimated by simulating the quantum circuits. For this aim, we use the Bayesian approach in which the likelihood functions are needed, and they are obtained by simulating the appropriate quantum circuits. The precision of four different definite photon-number states of light, which all possess six photons, is compared. The measurement scheme that we have considered is counting the number of photons detected after the final beam splitter of the interferometer, and photon loss is modeled by using fictitious beam splitters in the arms of the interferometer. Our results indicate that three of the four definite photon-number states considered can have better precision than the standard interferometry limit whenever the photon loss rate is in a specific range. In addition, the Fisher information for the four definite photon-number states in the setup is also estimated to check the optimality of the chosen measurement scheme. [ABSTRACT FROM AUTHOR]

To solve the problem of multiple sound recognition in the application of Sagnac optical fiber acoustic sensing system, a multi-source synchronous recognition algorithm was proposed, which combined the VMD (variational modal decomposition) algorithm and MFCC (Mel-frequency cepstral coefficient algorithm) algorithm to pre-process the photoacoustic sensing signal, and uses BP neural network to recognize the photoacoustic sensing signal. The modal analysis and feature extraction theory of photoacoustic sensing signal based on the VMD and MFCC algorithms were presented. The signal recognition theory analysis and system recognition program design were completed based on the BP neural network. Signal acquisition of different sounds and verification experiments of the recognition system have been carried out in a laboratory environment based on the Sagnac fiber optic sound sensing system. The experimental results show that the proposed optical fiber acoustic sensing signal recognition algorithm has a simultaneous recognition rate better than 96.5% for six types of sounds, and the optical acoustic signal recognition takes less than 5.3 s, which has the capability of real-time sound detection and recognition, and provides the possibility of further application of the Sagnac-based optical fiber acoustic sensing system. [ABSTRACT FROM AUTHOR]

Symmetry breaking of light states is of interest for the understanding of nonlinear optics, photonic circuits, telecom applications and optical pulse generation. Here we demonstrate multi-stage symmetry breaking of the resonances of ring resonators with Kerr nonlinearity. This multi-stage symmetry breaking naturally occurs in a resonator with bidirectionally propagating light with orthogonal polarization components. The derived model used to theoretically describe the system shows that the four circulating field components can display full symmetry, full asymmetry, and multiple versions of partial symmetry, and are later shown to result in complex oscillatory dynamics - such as four-field self-switching, and unusual pulsing with extended delays between subsequent peaks. To highlight a few examples, our work has application in the development of photonic devices like isolators and circulators, logic gates, and random numbers generators, and could also be used for optical-sensors, e.g. by further enhancing the Sagnac effect. Spontaneous symmetry breaking of light in ring resonators are of broad interest due to its fundamental properties in nonlinear optics and its potential applications in photonic circuits and optical communications. This work reports the multi-stage symmetry breaking in ring resonators with Kerr nonlinearity, which can find applications such as photonic isolators and circulators, logic gates, and random number generators. [ABSTRACT FROM AUTHOR]

Rotating systems in thermal equilibrium are ubiquitous in our world. In the context of high-energy physics, rotations would affect the phase structure of quantum chromodynamics (QCD). However, the standard Monte Carlo methods in rotating systems are problematic because the chemical potentials for the angular momenta (angular velocities) cause sign problems even for bosonic variables. In this article, we demonstrate that the complex Langevin method (CLM) may overcome this issue. We apply the CLM to the Yang–Mills (YM)-type one-dimensional matrix model (matrix quantum mechanics) that is a large- N reduction (or dimensional reduction) of the (D + 1)-dimensional U(N) pure YM theory [bosonic Banks–Fischler–Shenker–Susskind (BFSS) model]. This model shows a large- N phase transition at finite temperature, which is analogous to the confinement/deconfinement transition of the original YM theory, and our CLM predicts that the transition temperature decreases as the angular momentum chemical potential increases. In order to verify our results, we compute several quantities via the minimum sensitivity method and find good quantitative agreements. Hence, the CLM works properly in this rotating system. We also argue that our results are qualitatively consistent with a holography and the recent studies of the imaginary angular velocity in QCD. As a byproduct, we develop an analytic approximation to treat the so-called "small black hole" phase in the matrix model. [ABSTRACT FROM AUTHOR]

The Sagnac effect can be demonstrated with light propagating either along a circular contour or, as done by Wang et al., back and forth along a linear contour. In the linear Sagnac effect, the emitter–receiver device is in motion relative to the contour where light propagates. In the reciprocal linear Sagnac effect (RLSE), the device is stationary and the contour is in motion. When the contour changes direction of motion, some special features of the linear Sagnac effect are not fully reciprocal to the RLSE, which foresees variations of the first order in v⁄cv/c in the round-trip time taken by a light signal to cover the contour. The RLSE can be tested with present technology and, if confirmed experimentally, it might have interesting technological applications. Presently, it can be important for testing light-speed invariance, simultaneity, and the relativity principle.

In the One-Way Linear Effect, the round-trip time interval T0′ taken by light to propagate around a moving linear closed contour, is measured by a device. If the contour changes velocity by Δv, the round-trip interval T′(X′,Δv) turns out to depend on the device position X′ and Δv. The variation ΔT′=T′(X′,Δv)−T0′, related to Δv/c, is experimentally observable by means of standard interferometry, ring laser techniques, or high precision time-delay detectors of light pulses. Being sensitive to velocity variations, if experimentally confirmed the One-Way Linear Effect may have relevant applications in inertial guidance systems and related areas. Furthermore, the One-Way Linear Effect can be used to confirm Lorentz invariance by testing relative simultaneity versus absolute simultaneity.

Objectives: With the ultra-high precision time and frequency signals provided by space high precision time and frequency system, series of space-to-ground time and frequency transfer and fundamental physics experiments can be carried out to support high precision validation of relativity and related theories. Methods: First, theoretical derivation and simulation analysis are conducted on the time and frequency transfer algorithm of space laser links. Theoretical formula of space-to-ground laser two way time transfer are reviewed, and the advantages and disadvantages of X-type and Lambda-type approaches are compared and analyzed. Then, the impact of relativistic effects on the conversion between proper time and coordinate time is discussed for the specific orbital height of China space station. Finally, the impact of space-to ground time and frequency transfer discontinuity on the stability evaluation of high-precision atomic clocks onboard space stations is discussed. Results: The results show that: (1) Lambda-type two-way time transfer based on satellite laser ranging can make up the distance difference of first-order Doppler effect on the uplink and downlink, and increase of Sagnac effect can be ignored. (2) The relativistic effect of the conversion between proper time and coordinate time for satellite ground time transfer makes high demands on the velocity accuracy of space station positions, in order to achieve 1×10-18 frequency transfer accuracy, geocentric distance accuracy of 1 dm and speed accuracy of 0.1 mm/s of space station is required; (3) Influenced by the visibility of space stations to the ground, it is not possible to evaluate the medium term stability of atomic clocks with only the observation data of domestic stations satellite for space-to-ground links. Conclusions: High precision navigation solution is important to ensure high-precision time and frequency transfer between space and ground. How to optimize navigation algorithms and use various payloads onboard to achieve high-precision position and velocity solution is a key issue that needs to be studied. [ABSTRACT FROM AUTHOR]

In this research, the angular rotation speed in a passive photonic gyroscope based on the combination of side nanoring resonators and compensating waveguides has been analyzed by creating nonlinear effects in the control factors of the rings using the Sagnac effect. This structure consists of a central waveguide, two identical square resonators, and an almost U-shaped waveguide. The U-shaped waveguide causes coupling between the two resonators in a counterclockwise (CCW) mode. In this structure, a phase shift has been created in the output from the interference of two clockwise (CW) and CCW waves inside the resonators, and according to this phase shift and the central wavelength, the angular rotation speed has been estimated. In the proposed design of the gyroscope, by managing the nonlinear effects in the radius and refractive index (RI) of the coupling and inner rods, we have been able to control the changes in power, phase, and wavelength of the output from the device. With the increase in the intensity of power, the output power has an increasing slope at first, and at the point of creating a nonlinear effect in the sensor, the output power slope decreases. Also, this nonlinear effect directly affects the output phase of the structure. The maximum angular rotation speed in this gyroscope was 6. 6 8 × 1 0 8 ∘ /s. By changing the RI of the inner rods from 3.2 to 3.7, the maximum output-to-input power ratio changes from 0.38 W/ μ m2 to 0.75 W/ μ m2. By changing the radius of the coupling rods from 93 nm to 97 nm, the maximum power ratio decreases from 0.78 W/ μ m2 to 0.55 W/ μ m2. The field distribution profile and photonic bandgap in this gyroscope have been analyzed using the finite-difference time-domain (FDTD) and plane-wave expansion (PWE) methods, respectively. Also, the gyroscope has a footprint of 163.5  μ m2. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In axistationary, asymptotically flat spacetimes, zero angular momentum observers (ZAMOs) define an absolute standard of non-rotation locally, as can be verified by the absence of any Sagnac effect for these observers. Nevertheless, we argue that on a global scale the only physically meaningful concept is that of relative rotation. The argument is substantiated by solving Einstein's equations for an approximate thin shell model, where we maintain a degree of freedom, by relaxing the natural assumption of vanishing rotation at asymptotic infinity, at the outset of the analysis. The solution reveals that Einstein's equations only determine differences in the rotation rate of ZAMOs, thereby establishing the concept of relative rotation globally. The interpretation of rotation as relative in a global context is inherently linked to the freedom to transform between coordinate systems rotating relative to each other, implying that an arbitrary ZAMO located at any radius may claim to be the one that is non-rotating on a global scale, and that the notion of an asymptotic Lorentz frame relative to which one may measure absolute rotation is devoid of any meaning. The concept of rotation in Kerr spacetime is then briefly discussed in the context of this interpretation. [ABSTRACT FROM AUTHOR]

We theoretically demonstrate an ultrasensitive and ultrahigh-resolution biomolecule mass sensing based on a spinning resonator system, which includes a spinning whispering-gallery-mode (WGM) optomechanical cavity and an auxiliary optical cavity. When the WGM cavity is spinning along the clockwise or counterclockwise direction, the cavity field will undergo different Sagnac effect. If the Sagnac effect and the auxiliary optical cavity are simultaneously taken into consideration, not only the line width of the transmission spectrum is significantly squeezed, but also the transmission intensity will be extremely enhanced, which indicates an ultrasensitive and ultrahigh-resolution mass sensor. When the mass of external biomolecules (such as baculovirus or coronavirus) is deposited on the resonator, their mass can be determined by tracking the resonance frequency shifts in the transmission spectrum. Thus, our research can provide a method to classify kinds of viruses, especially can be used to identify 2019-nCoV. [ABSTRACT FROM AUTHOR]

As a fundamental optical approach to interferometry, Sagnac interference has been widely used for reflection manipulation, precision measurements, and spectral engineering in optical systems. Compared to other interferometry configurations, it offers attractive advantages by yielding a reduced system complexity without the need for phase control between different pathways, thus offering a high degree of stability against external disturbance and a low wavelength dependence. The advance of integration fabrication techniques has enabled chip-scale Sagnac interferometers with greatly reduced footprint and improved scalability compared to more conventional approaches implemented by spatial light or optical fiber devices. This facilitates a variety of integrated photonic devices with bidirectional light propagation, showing new features and capabilities compared to unidirectional-light-propagation devices, such as Mach–Zehnder interferometers (MZIs) and ring resonators (RRs). This paper reviews functional integrated photonic devices based on Sagnac interference. First, the basic theory of integrated Sagnac interference devices is introduced, together with comparisons to other integrated photonic building blocks, such as MZIs, RRs, photonic crystal cavities, and Bragg gratings. Next, the applications of Sagnac interference in integrated photonics, including reflection mirrors, optical gyroscopes, basic filters, wavelength (de)interleavers, optical analogues of quantum physics, and others, are systematically reviewed. Finally, the open challenges and future perspectives are discussed. [ABSTRACT FROM AUTHOR]

Compact interferometers based on waveguiding structures have found countless applications in refractive index measurements, chemical sensing, as well as temperature and pressure measurements. The most common fiber devices are based on Mach–Zehnder interferometry and Michelson interferometry—two design concepts that can readily be implemented using simple fiber optic components, such as mode splitters and combiners, fiber optic gratings, and fiber tapers, among others. Fiber interferometry can also be conducted based on the Sagnac effect and the Young (double-slit) interferometer. In this review, we examine and compare over 400 fiber optic interferometers as well as more than 60 fiber optic refractive sensors based on fiber optic cavities. Even though many of the devices show temperature-, strain-, and pressure-sensitivity, we focus our review on refractive index measurements, as these are the most common applications. Many devices were characterized by their inventors using their sensitivity to refractive index changes. While the sensitivity is an important characteristic of the device, it does not easily relate to the smallest resolvable refractive index change or the limit of detection when applied to chemical measurements. Instead, we propose here that one should use the figure of merit, which is defined through the refractive index sensitivity and the width of an interferometer fringe. Using simple assumptions, we were able to mathematically relate the sensitivity and the figure of merit to common design parameters, such as the length of the interferometer arms, the operating wavelength, refractive indices of the fiber and the sample, as well as an overlap parameter, which describes the fraction of the guided wave in the sensing arm that interacts with the sample. We determined this overlap parameter for each reviewed device from the reported interferograms. Our meta-analysis provides for the first time simple and easily applicable guidance to increase the figure of merit of fiber optic interferometers and fiber optic cavities with regard to their ability to detect small refractive index changes. A high figure of merit allows measuring very small refractive index changes such as those of gases at different pressures or of very dilute solutions. [ABSTRACT FROM AUTHOR]

The paper discusses the modern state of optical resonator gyroscopes. The basic concept of this type of gyros is described. The main approaches to their design and the method for angular rate measurement are considered, with the main focus made on the pioneer and most popular approach based on the use of phase modulation spectroscopy and a tuned laser. An alternative approach based on low-coherent sources of light is also analyzed. The main sources of measurement errors and the methods to overcome them are considered. The best value of random drift has been so far achieved using fiber ring resonators: 2.0 deg/h with the ring diameter 60 mm and the integration time 1 s, and 1.23 deg/h in 5 s; with the diameter 120 mm, 0.37 deg/h has been achieved with the integration time 1 s and 0.06 deg/h with 370 s. The reasons that currently hinder the commercial development of optical resonator gyros are studied. [ABSTRACT FROM AUTHOR]

We investigate the coherent optical propagation in a photonic molecule spinning optomechanical system consisting of two whispering gallery microcavities in which one of the optical cavities is a spinning optomechanical cavity and the other one is an ordinary auxiliary optical cavity. As the optomechanical cavity is spinning along the clockwise or counterclockwise direction, the cavity field can undergo different Sagnac effects, which accompanies the auxiliary optical cavity, together influencing the process of the evolution of optomechanically induced transparency and its related propagation properties, such as fast and slow light effects. The numerical results indicate that the enhanced slow and fast light and the conversion from fast to slow light (or slow to fast light) are determined by the spinning direction of the optomechanical cavity and the coupling of the two optical cavities. The study affords further insight into the photonic molecule spinning optomechanical systems and also indicates promising applications in quantum information processing. [ABSTRACT FROM AUTHOR]

Frequency lock-in-induced deadband phenomena are major problems of ring laser gyroscopes (RLGs), which deteriorate linear responses to changes in the applied rotation rate. In this work, the frequency lock-in phenomenon occurring in the RLG was successfully investigated by compensating for the Sagnac effect through frequency analysis using a newly defined error function. Integrative and generalized viewpoints from the analyzed results provide new possibilities for relevant performance improvements of optical gyroscopes, as well as a deeper understanding of locked states in principle aspects. [ABSTRACT FROM AUTHOR]

We discuss the polarization of gravitational radiation within the standard framework of linearized general relativity. The recent experimental discovery of gravitational waves provides the impetus to revisit the implications of the spin-rotation-gravity coupling for polarized gravitational radiation; therefore, we consider the coupling of the helicity of gravitational waves to the rotation of an observer or the gravitomagnetic field of a rotating astronomical source. Observational possibilities regarding polarization-dependent effects in connection with future gravitational wave detectors are briefly explored. [ABSTRACT FROM AUTHOR]

A straight-line-type Sagnac optic fiber acoustic sensing system is proposed in this paper to adopt the application needs of no man's plateau borderline for monitoring mechanical invasion. The Sagnac interference fiber loop is replaced by a straight-line fiber and a 1 × 2 coupler, and the length of the Sagnac interference fiber loop is shortened by close to 50%. The influences of delay fiber and sensing fiber on the sensing system are analyzed by theory calculation and simulation and the optimal lengths of delay fiber and sensing fiber were decided. The experiment system was set, and the sensing fiber was wound into titanium alloy cylinder to compose the sensing element. Experimental results show that the sensing system has a good response to 50−8000 Hz and 70 dB sinusoidal acoustical signals and can well distinguish the signals of different frequencies. Using a small-scale helicopter audio signal as the acoustical signal, the test results show that the response curve is consistent with the simulation results and the sensitivity reaches 30.67 mV/Pa. [ABSTRACT FROM AUTHOR]

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The article discusses a 2022 hybrid three-axis accelerometer with the quantum advantage to measure the full acceleration vector tracking in geophysics and economic geology. Topics covered include the combination of three interferometer measurements with navigation-grade accelerometer triad to record the acceleration vector. Also noted is the method's potential applications with quantum sensors and in future inertial navigation units.

We propose a passive optical gyroscope based the Sagnac effect that consists of a sequence of coupled high-quality factor resonators and bus waveguides. In this proposed gyro, using Sagnac effect, the optimum phase shift between two counter propagating beams is measured to sense parameter of structure. Using the high coupling property between the waveguides and the rings, the light is conducted at the operating wavelengths of the proposed gyroscope. Using numerical simulation, the key parameters of this proposed structure, including the output power of the drop ports, the quality factor of the rings, the output phase shift, the angular rotation rate, the transmission and the forbidden bands, according to the number of coupled integrated ring resonators, was analyzed. [ABSTRACT FROM AUTHOR]

• A microscopic model of a Terbium-doped magneto-refractive silica fiber was proposed. • An magneto-refractive measurement system was designed for magnetic field sensing. • The Terbium-doped silica fiber has potential in magnetic field sensing applications. In this study, the magneto-refractive effect (MRE) of a terbium-doped fiber (TDF) that can be employed for magnetic field sensing was investigated. A microscopic model of a terbium doped magneto-refractive silica fiber was proposed, and the relationship between the refractive index (RI) of the fiber and its magnetic field was numerically studied. The MRE of the TDF was then characterized using an electronic holographic magneto-refractive measuring system. The characterization results showed that the RI of the TDF increased linearly at a rate of 2.13 × 10−5 RIU/mT as the magnetic field intensity increased from 0 to 10 mT. An all-solid-state magneto-refractive measurement system based on a fiber-optic Sagnac interferometer was designed for magnetic field sensing, which linearly responded to the applied magnetic field. The relationship between the dielectric tensor and magnetic moment of the fiber was analyzed. Based on the finite difference algorithm, the change in the RI and dielectric tensor of the optical fiber under a magnetic field was simulated. Results indicated that the proposed fiber has potential use in high-sensitive magnetic field sensing applications. [ABSTRACT FROM AUTHOR]

An ultra-sensitive temperature sensor was proposed and demonstrated by inserting polarization maintaing fibers (PMFs) into cascading Sagnac fiber loops. Effect of the length of PMFs in an individual Sagnac loop on the temperature sensitivity of the sensor was firstly studied. As the PMF length reduces, the sensitivity increases. In the PMFs cascade Sagnac loops, the closer the lengths of the two sections of PMFs embedded in the Sagnac loops, the wider the free spectral range, resulting stronger Vernier effect and thus higher sensitivity. The temperature sensitivity of the cascade Sagnac loops is ∼ -44.28 nm/°C, a 27-fold increase than that of an individual Sagnac loop (∼-1.64 nm/°C). This newly developed temperature sensor has the merits of simple structure, high sensitivity and easy operation, and good competitiveness in the sensing field. • The sensitivity of the sensor is as high as 44.28 nm/°C. • The sensing structure is easy to realize. • The sensitivity is enhanced 27 times by Vernier effect. [ABSTRACT FROM AUTHOR]

This paper proposed and investigated a sensor that could simultaneously measure temperature and magnetic fields. The key component of this sensor was a photonic crystal fiber with a length of only 1 cm, whose air holes were arranged in a circular lattice symmetry. In order to increase the birefringence of the fiber, we introduced well-designed point defects into the photonic lattice. The deficient pores were filled with a magneto-fluidic material (MF) that sensed temperature and magnetic fields through changes in its refractive index. The outer layer of the fiber cladding was coated with a thin film of Indium tin oxide (ITO), which was in direct contact with ethanol. The surface plasmon resonance created by ITO was used to achieve dual-parameter demodulation and solve the cross-sensitivity problem. The photonic crystal fiber and other optical components made up a Sagnac interferometer, which was used to measure the transmission spectrum of the Sagnac interference. At the same time, the loss spectrum due to the surface plasmon resonance was measured. The variation in temperature and magnetic field was directly related to the shift in the resonance wavelengths of the transmission and loss spectra, thus enabling simultaneous dual-parameter measurements. We investigated the sensing performance of the sensor numerically. The results showed a wavelength sensitivity of 7.6 nm/°C and 0.75 nm/mT, with a resolution of 1.316 × 10−3 °C and 1.333 × 10−3 mT for temperature and magnetic field, respectively. Compared with other sensors, the key component of the proposed sensor is only 1 cm in length, which makes it compact and easy to manufacture. The geometric parameters, such as the position and radius of the pores, are less likely to deviate from the ideal values, which helps to reduce the impact of manufacturing tolerances on the sensing performance. [ABSTRACT FROM AUTHOR]

A photon source is located in a rotating waveguide. An absorber with a sharp absorbing frequency absorbs some of the emitted photons. This decreases the number of photons which are detected by a detector. The frequency (energy) spectrum measured in the absorber depends on the setup (the positions of the source and the detector), and this spectrum determines the amount of absorption. The shifts are calculated for different configurations. Among other things, it is seen that even if the source and the absorber are at rest (while the waveguide is rotating), there is a nonzero frequency shift. [ABSTRACT FROM AUTHOR]

Bushing plays a significant role in insulation and mechanical support for power transformers. Its working state is closely related to the reliable operation of power transformers. To overcome the electromagnetic interference and security risks during sensor installation, a Sagnac interference optical technique for partial discharge (PD) detection is proposed in this paper. By establishing a simulation model of the sensing structure, it is verified that output signal amplitude varies periodically with the length of sensing and delay fibers. Moreover, the output value decreases with increasing probe radius. The results show that a delay fiber of 1.5 km, a sensing fiber of 3 m, and a bending radius of 5 mm are optimal parameter combinations to detect PD in a 72.5 kV defective bushing. In addition, consistent detection waveforms induced by both internal and external defects are obtained by the optical sensor and high frequency current transformer (HFCT) simultaneously, then the effectiveness of the optical sensor on detecting PD signals for bushing is verified. It is of great help to carry out online monitoring of bushing insulation defects through optical non-destructive installation. [ABSTRACT FROM AUTHOR]

We show that the one-way speed of light, along an open contour AB on the uniformly rotating Earth, is observable. Our approach exploits the property of the Sagnac effect that can measure the Earth's local angular velocity and, correspondingly, the peripheral speed of the contour AB relative to Earth Centered Inertial (ECI) frame. Light speed variations, measured on the rotating Earth, may be related to the velocity w of the ECI frame relative to a hypothetical preferred frame. Since it is possible to test Einstein's postulate of a universal light speed, standard special relativity is confirmed to be a viable falsifiable theory.