Analysis of the Anomalous Brillet and Hall Experimental Result

The persistent, second-order, anomalous signal found in the Brillet and Hall experiment is derived by applying 4D differential geometry in the rotating earth frame. By incorporating the off diagonal time-space components of the rotating frame metric directly into the analysis, rather than arbitrarily transforming them away, one finds a signal dependence on the surface speed of the earth due to rotation about its axis. This leads to a Brillet-Hall signal prediction in remarkably close agreement with experiment. No signal is predicted from the speed of the earth in solar or galactic orbit, as the associated metric for gravitational orbit has no off diagonal component. To corroborate this result, a repetition by other experimentalists of the Brillet-Hall experiment, in which the test apparatus turns with respect to the earth surface, is urged.     

New Perspectives on the Relativistically Rotating Disk and Non-Time-Orthogonal Reference Frames

The rotating disk problem is analyzed on the premise that proper interpretation of experimental evidence leads to the conclusion that the postulates upon which relativity theory is based, particularly the invariance of the speed of light, are not applicable to rotating frames. Different postulates based on the Sagnac experiment are proposed, and from these postulates a new relativistic theory of rotating frames is developed following steps similar to those initially followed by Einstein for rectilinear motion. The resulting theory agrees with all experiments, resolves problems with the traditional approach to the rotating disk, and exhibits both traditionally relativistic and non-relativistic characteristics. Of particular note, no Lorentz contraction exists on the rotating disk circumference, and the disk surface, contrary to the assertions of Einstein and others, is found to be Riemann flat. The variable speed of light found in the Sagnac experiment is then shown to be characteristic of non-time-orthogonal reference frames, of which the rotating frame is one. In addition, the widely accepted postulate for the equivalence of inertial and non-inertial standard rods with zero relative velocity, used liberally in prior rotating disk analyses, is shown to be invalid for such frames. Further, the new theory stands alone in correctly predicting what was heretofore considered a spurious non-null effect on the order of 10^–13 found by Brillet and Hall in the most accurate Michelson-Morley type test to date. The presentation is simple and pedagogic in order to make it accessible to the non-specialist.     

The Sagnac Phase Shift Suggested by the Aharonov-Bohm Effect for Relativistic Matter Beams

The phase shift due to the Sagnac Effect, for relativistic matter beams counter-propagating in a rotating interferometer, is deduced on the bases of a formal analogy with the Aharonov-Bohm effect. A procedure outlined by Sakurai, in which non relativistic quantum mechanics and Newtonian physics appear together with some intrinsically relativistic elements, is generalized to a fully relativistic context, using the Cattaneo's splitting technique. This approach leads to an exact derivation, in a self-consistently relativistic way, of the Sagnac effect. Sakurai's result is recovered in the first order approximation.     

A Direct Kinematical Derivation of the Relativistic Sagnac Effect for Light or Matter Beams

The Sagnac time delay and the corresponding Sagnac phase shift, for relativistic matter and electromagnetic beams counter-propagating in a rotating interferometer, are deduced on the ground of relativistic kinematics. This purely kinematical approach allows to explain the universality of the effect, namely the fact that the Sagnac time difference does not depend on the physical nature of the interfering beams. The only prime requirement is that the counter-propagating beams have the same velocity with respect to any Einstein synchronized local co-moving inertial frame.     

On the Anistropy of the Speed of Light on a Rotating Platform

The paper discusses a recently posed paradox in relativity concerning the speed of light as measured by an observer on board a rotating turn-table. The counter-intuitive problem put forward by F. Selleri concerns the theoretical prediction of an anisotropy in the speed of light in a reference frame comoving with the edge of a rotatiing disc even in the limit of zero acceleration. The paradox not only challenges the internal consistency of the special relativity theory but also undermines the basic tenet of the conventionality of simultaneity thesis of relativity. The present paper resolves the issue in a novel way by recasting the original paradox in the Galilean world and thereby revealing, in a subtle way, the weak points of the reasonings leading to the fallacy. As a background the standard and the non-standard synchronies in the relativistic as well as in the Galilean world are discussed. In passing, this novel approach also clarifies (contrary to often made assertions in the literature) that the so-called desynchronization of clocks cannot be regarded as the root cause of the Sagnac effect. Finally in spite of the flaw in the reasonings leading to the paradox Selleri's observation regarding the superiority of the absolute synchrony over the standard one for a rotation observer has been upheld.     

Relativistic Rotation: A Comparison of Theories

Alternative theories of relativistic rotation considered viable as of 2004 are compared in the light of experiments reported in 2005. En route, the contentious issue of simultaneity choice in rotation is resolved by showing that only one simultaneity choice, the one possessing continuous time, gives rise, via the general relativistic equation of motion, to the correct Newtonian limit Coriolis acceleration. In addition, the widely dispersed argument purporting Lorentz contraction in rotation and the concomitant curved surface of a rotating disk is analyzed and argued to be lacking for more than one reason. It is posited that not by theoretical arguments, but only via experiment can we know whether such effect exists in rotation or not. The Coriolis/simultaneity correlation, and the results of the 2005 experiments, support the Selleri theory as being closest to the truth, though it is incomplete in a more general applicability sense, because it does not provide a global metric. Two alternatives, a modified Klauber approach and a Selleri–Klauber hybrid, are presented which are consistent with recent experiment and have a global metric, thereby making them applicable to rotation problems of all types.     

On Local and Global Measurements of the Speed of Light on Rotating Platforms

The paper shows that, conceptually and operationally, the speed of light measured locally in the inertial comoving frame of a point on the rim of a rotating disk is different from the one measured globally for a round trip along the rim, obtained dividing the length of the rim (as measured in the relative space of the disk) by the time of flight of the light beam (as measured by a clock at rest on the disk). As a consequence, contrary to some recent claims, the anisotropy found in the global value, obtained by the above procedure, in no way conflicts with the local isotropy, and the internal consistency of the special relativity theory remains unchallenged.     

Sagnac效应在光纤水听器中的应用

本文介绍了Ｓａｇｎａｃ效应组成的光纤水听器原理，着重推导了声压作用下的光纤水听器的相位变化关系，并在此基础上对比了Ｓａｇｎａｃ光纤水听器与Ｍａｃｈ－Ｚｅｈｎｄｅｒ光纤水听器，结果表明Ｓａｇｎａｃ光纤水听器在低频段的灵敏度及其实现的简易性上具有很大优势。     

Sagnac效应在光纤水听器中的应用

本文介绍了由Sagnac效应组成的光纤水听器原理，着重推导了声压作用下的光纤水听器的相位变化关系．并在此基础上对比了Sagnac光纤水听器与Mach-Zehnder光纤水听器，结果表明Sagnac光纤水听器在低频段的灵敏度及其实现的简易性上具有很大优势．     

Physical Dimensions/Units and Universal Constants: Their Invariance in Special and General Relativity

The theory of physical dimensions and units in physics is outlined. This includes a discussion of the universal applicability and superiority of quantity equations. The International System of Units (SI) is one example thereof. By analyzing mechanics and electrodynamics, it naturally leads one, besides the dimensions of length and time, to the fundamental units of action $\mathfrak{h}$, electric charge q, and magnetic flux ?. Also, $q\times ?=\text{action}$ and $q/?=1/\text{resistance}$ are known. These results of classical physics suggests to look into the corresponding quantum aspects of q and ? (and also of $\mathfrak{h}$): The electric charge occurs exclusively in elementary charges e, whereas the magnetic flux can have any value; in specific situations, however, in superconductors of type II at very low temperatures, ? appears quantized in the form of fluxons (Abrikosov vortices). And $\mathfrak{h}$ leads, of course, to the Planck quantum h. Thus, one is directed to superconductivity and, because of the resistance, to the quantum Hall effect. In this way, the Josephson and the quantum Hall effects come into focus quite naturally. One goal is to determine the behavior of the fundamental constants in special and in general relativity.     

The centennial of the Sagnac experiment in the optical regime: From a tabletop experiment to the variation of the Earth's rotation

The investigation of non-reciprocal behavior of optical beams in a rotating reference frame was the main motivation of the historic tabletop experiment of George Sagnac. His ground-breaking experiment was extended to a very large installation more than a decade later, which was sensitive enough to allow Michelson, Pearson and Gale to resolve the rotation rate of the Earth by an optical interferometer. With the advent of lasers in the early sixties of the last century, rotating laser cavities with a ring structure demonstrated superior performance and very soon matured to a point where mechanical gyroscopes were quickly superseded by laser gyroscopes in aircraft navigation. When vastly upscaled ring lasers were taken back to the laboratory at the end of the 20th century, the goal of applying the Sagnac effect to geodesy for the monitoring of tiny variations of Earth's rotation was the main motivation. The large-ring laser G, which is the most stable instrument out of a series of instruments built by the New Zealand–German collaboration, routinely resolves the rotation rate of the Earth to better than eight orders of magnitude. Since G is directly referenced to the Earth rotation axis, the effect of diurnal polar motion, the Chandler and the Annual wobbles as well as tilts from the solid Earth tides can be found in the interferogram obtained from the ring laser. G has also demonstrated high sensitivity to rotations associated with seismic events. The toroidal eigenmodes of the Earth when they are excited by large earthquakes have been resolved. A surprisingly large amplitude has been measured for Love wave signals contained in the microseismic background signal. This paper summarizes the recent development of highly sensitive large Sagnac gyroscopes, and presents unique results from the measurements of rotations of the earth.     

Analysis of polarization-independent tunable optical comb filter by cascading MZI and phase modulating Sagnac loop

A novel scheme of tunable optical comb filter constructed by cascading a polarization-swapping MZI and a phase modulating Sagnac loop is proposed. The key features of this comb filter design are its polarization-independence and high speed in wavelength tuning. The wavelength tunability can be readily achieved by incorporating an electro-optic phase modulator into the Sagnac loop. In addition, the filter can be made amplitude adjustable as well. The filter will be desirable for multi-wavelength fiber lasers, multi-channel optical signal processing and optical WDM systems.     

SOA-assisted Sagnac switch and investigation of its roadmap from 10 to 40 GHz

Future broadband optical communications networks will rely on all-optical switches to perform a set of processing functions exclusively in the optical domain. Interferometric optical switches using semiconductor optical amplifier (SOA) nonlinearities can perform efficient optical switching with few tens of fJ control energies and short fiber lengths allowing for monolithic integration. In this paper we present work performed with a three terminal SOA-assisted Sagnac interferometer. We review all-optical Boolean AND and XOR logic results at 10 GHz and 10 Gb/s for full duty cycle and pseudo-random data pattern operation, respectively, achieved with adequate contrast ratios, remarkably low switching energies and low pattern dependence. The ability of the device to be cascaded was proved up to 10 GHz by recirculating stably for hours arbitrary pattern profiles. Finally, and in view of the extension of photonic networks single channel data rates beyond 40 Gb/s, the performance of the switch was simulated in terms of its critical parameters. The obtained results showed that full switching operation at 40 GHz or higher is feasible either by deploying gain recovery reduction techniques in bulk and quantum well SOAs or alternatively other technologically advanced optical devices, such as quantum dot SOAs.     

On the Conventionality of Simultaneity

Starting from the experimental fact that light propagates over a closed path at speed c (L/c law), we show to what extent the isotropy of the speed of light can be considered a matter of convention. We prove the consistence of anisotropic and inhomogeneous conventions, limiting the allowed possibilities. All conventions lead to the same physical theory even if its formulation can change in form. The mathematics involved is that of gauge theories and the choice of a simultaneity convention is interpreted as a choice of the gauge. Moreover, we prove that a Euclidean space where the L/c law holds, gives rise to a spacetime with Minkowskian causal structure, and we exploit the consequences for the causal approach to the conventionality of simultaneity.     

基于低双折射光子晶体光纤Sagnac干涉仪的超低温度系数扭曲传感器

研究了低双折射光子晶体光纤中由光纤扭曲造成的圆双折射效应,并应用Sagnac干涉仪结构设计了扭曲传感器.在Sagnac环中的光子晶体光纤上施加机械压力引入初始线双折射并产生正弦干涉光谱,再扭曲光纤产生圆双折射使干涉光谱随扭曲角度移动.光谱峰值波长随扭曲角度变化符合Sinc函数关系,理论分析与实验相符.传感器灵敏度为1....     

基于低双折射光子晶体光纤Sagnac干涉仪的超低温度系数扭曲传感器

研究了低双折射光子晶体光纤中由光纤扭曲造成的圆双折射效应,并应用Sagnac干涉仪结构设计了扭曲传感器.在Sagnac环中的光子晶体光纤上施加机械压力引入初始线双折射并产生正弦干涉光谱,再扭曲光纤产生圆双折射使干涉光谱随扭曲角度移动.光谱峰值波长随扭曲角度变化符合Sinc函数关系,理论分析与实验相符.传感器灵敏度为1.00 nm/°,分比率为0.01°,并具有超低的温度系数-0.5 pm/℃.     

Sagnac型光学电压互感器传感单元非线性误差分析与抑制

基于Pockels效应的Sagnac型光学电压互感器的传感单元是由法拉第准直旋光器和BGO晶体构成,其中由偏振串扰引入的非线性误差是影响互感器测量精度及稳定性的主要误差来源。为了抑制传感单元存在的非线性误差,从主要光路器件及器件间的耦合点中分析产生偏振串扰的非理想耦合点及耦合机理,并提取表征该耦合点的误差特征参量,建立各非理想耦合点的传输模型,由此推导由传感单元偏振串扰引入的非线性误差模型,数值仿真并实验验证非理想偏振耦合对互感器性能的影响。在此基础上,提出了由BGO晶体敏感环境振动、温度波动等产生的非线性误差的抑制方法,实验结果验证了抑制方法的有效性。     

主动相位偏置折叠型萨尼亚克光纤传感阵列时分复用技术

针对折叠结构萨尼亚克(Sagnac)光纤传感阵列存在噪声光与信号光混叠的问题,提出了一种主动相位偏置时分复用方案.在传统梯形结构传感阵列的基础上,通过调整总线光纤的长度关系和附加延迟光纤的方法,使噪声光和信号光依次交替返回而不会发生混叠.进一步分析表明,通过调整延迟光纤环的长度,可以使输入光脉冲的重复频率达到标准时分复用系统重复频率的二分之一.整个阵列的相位偏置由一个与输入光脉冲同步的相位调制信号驱动集成光学芯片实现.实验演示了一个两基元的传感阵列,最小时间间隔为331.25 ns,输入光脉冲重复频率可达754.727 kHz,在5 kHz处相位灵敏度为7.3μrad√(Hz),探头间串扰约为-51.75 dB.     

Temperature-Induced Changes of Sensitivity in the Unbalanced Hi-Bi Fiber Sagnac Interferometer

A temperature sensor based on the unbalanced Hi-Bi fiber Sagnac interferometer is analyzed in the temperature interval 15 250 C. It is shown that the sensitivity of such a sensor exhibits irreversible changes at temperatures higher than 200 C. To achieve this, it is proposed to anneal the fiber at 200 C for 1.5 h to avoid hysteresis and extend the measured temperature interval. Measurements were done for the polymer-coating-induced birefringence and the residual stresses causing hysteresis. It is also shown that the sensor sensitivity is reduced by 27 % when stresses are removed.     

Instrument forward model of the modified Sagnac interferometer for atmospheric wind measurement

The instrument forward model of the modified super-wide-Sagnac imaging interferometer based on liquid crystals on Silicon (MSASII-LCoS) is developed as an integrated code package with Matlab language to simulate the images of satellite observations. There are five sub-models in the forward model including radiation model of O(¹S), orbit attitude, filter, interferometer and array detector. The principle of each sub-model is described separately and then the overall forward model equation is derived. The four simulation images are obtained. Based on the integrated signal level for the daytime observations, the apparent measurement error of wind is less than 3 m/s and the signal noise ratio (SNR) is greater than 194 with a binning of 2 × 25 pixels at the tangent height range of 70-190 km.