Bias error caused by broad-spectrum source and birefringence effect in fiber optical gyroscope

To analyze the bias error in the optical path of closed-loop polarization-maintaining (PM) fiber optical gyroscope (FOG), the interference signal term carrying only Sagnac phase shift in phase is divided into two types: one generated by interference between main wave-trains in the clock-wise (CW) direction and counter clock-wise (CCW) direction, and the other one generated by interference between secondary wave-trains in the CW and CCW direction. The residual term is discovered in the second kind, which is caused by synthetic effect of broad-spectrum source and birefringence effect in a FOG with the existence of crossovers. The main influencing factors and the effect on FOG performance of the bias error generated by the residual term is analyzed, and its suppression measures are promoted. Simulation result demonstrates that the bias error can be suppressed from about 0.02°/h to less than 2×10⁻⁴°/h at room temperature and its peak to peak value of variation with temperature can be suppressed to less than 4×10⁻⁴°/h, through matching birefringent fiber length and increasing the delay between modes of light source, which is small enough to meet the requirement of FOG with high performance.     

闭环光纤陀螺死区及光功率交扰误差的研究

数字闭环光纤陀螺引入的死区问题限制了其向更高性能惯性导航系统的应用。采用数学模型分析了数字闭环光纤陀螺死区的成因是反馈相关误差干扰,通过simulink仿真工具对死区现象进行了仿真,对比陀螺死区测试对模型进行了验证。以此为基础提出了电光合串扰造成死区的干扰模式,分析了干扰误差源的信号频域特征并使用频谱分析仪对受干扰的光功率信号进行了相关频点的测试,同时对比了干扰抑制后无死区的光功率信号相关频点的测试结果。通过抑制相关误差前后的测试结果对比,验证了与数字闭环反馈阶梯波相关的误差输入是死区形成的根本原因,除了电路交叉耦合之外,电路对光强的调制干扰也会造成死区问题。在采用针对干扰信号频率特性的退耦及PCB设计后,闭环光纤陀螺死区由0.2/h降低至0.02/h,满足系统应用需求。     

Effects of the substrate temperature on the properties of CuIn5S8 thin films

Structural, optical and electrical properties of CuIn₅S₈ thin films grown by thermal evaporation have been studied relating the effects of substrate heating conditions of these properties. The CuIn₅S₈ thin films were carried out at substrate temperatures in the temperature range 100-300 °C. The effects of heated substrate on their physico-chemical properties were investigated using X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), optical transmission and hot probe method. X-ray diffraction revealed that the films are strong preferred orientation along the (3 1 1) plane upon substrate temperature 200 °C and amorphous for the substrate temperatures below 200 °C. No secondary phases are observed for all the films. The composition is greatly affected by heated substrate. From the optical transmission and reflection, an important absorption coefficient exceeds 10⁵ cm⁻¹ at 800 nm was found. As increasing the substrate temperature, the optical energy band gap decreases from 1.70 eV for the unheated films to 1.25 eV for the deposited films at 300 °C. It was found that CuIn₅S₈ thin film is an n-type semiconductor at 250° C.     

单光纤光纤陀螺误差分析

单光纤光纤陀螺采用的是单光纤在线制作技术。由于这种方法是把所有的光器件都放在一根光纤上制作,因此各光器件的连接处没有融接点,并且光器件的性能可在线控制。在分析其结构的基础上建立了开环FOG的光学模型,并进行了误差分析。指出了单光纤光纤陀螺方案是低成本、高可靠性、易于工程化的一种方案。     

Numerical and experimental investigations of splat geometric characteristics during oblique impact of plasma spraying

Splats are obtained on the substrates inclined at different angles (0°, 20°, 40° and 60°) by plasma spraying process and characterized by SEM and WYKO^® optical surface profiler. Numerical model is developed using CFD software FLOW-3D^® to simulate the process of droplet impact, spreading and solidification onto the substrates. Splat characteristics such as spread factor, aspect ratio and fractional factor are defined and compared between simulation and experiment. Fair agreements are obtained. In addition, the impacting behavior including spreading and solidification are analyzed in details from the simulation results. The rates of reduction in droplet kinetic energy during impact, spreading and solidification are also compared between different inclination angles.     

Planar quarter wave stacks prepared from chalcogenide Ge-Se and polymer polystyrene thin films

Planar quarter wave stacks based on amorphous chalcogenide Ge-Se alternating with polymer polystyrene (PS) thin films are reported as Bragg reflectors for near-infrared region. Chalcogenide films were prepared using a thermal evaporation (TE) while polymer films were deposited using a spin-coating technique. The film thicknesses, d∼165 nm for Ge₂₅Se₇₅ (n=2.35) and d∼250 nm for polymer film (n=1.53), were calculated to center the reflection band round 1550 nm, whose wavelengths are used in telecommunication. Optical properties of prepared multilayer stacks were determined in the range 400-2200 nm using spectral ellipsometry, optical transmission and reflection measurements. Total reflection for normal incidence of unpolarized light was observed from 1530 to 1740 nm for 8 Ge-Se+7 PS thin film stacks prepared on silicon wafer. In addition to total reflection of light with normal incidence, the omnidirectional total reflection of TE-polarized light from 8 Ge-Se+7 PS thin film stacks was observed. Reflection band maxima shifted with varying incident angles, i.e., 1420-1680 nm for 45° deflection from the normal and 1300-1630 nm for 70° deflection from the normal.     

Determination and analysis of dispersive optical constants of CuIn3S5 thin films

CuIn₃S₅ thin films were prepared from powder by thermal evaporation under vacuum (10⁻⁶ mbar) onto glass substrates. The glass substrates were heated from 30 to 200 °C. The films were characterized for their optical properties using optical measurement techniques (transmittance and reflectance). We have determined the energy and nature of the optical transitions of films. The optical constants of the deposited films were determined in the spectral range 300-1800 nm from the analysis of transmission and reflection data. The Swanepoel envelope method was employed on the interference fringes of transmittance patterns for the determination of variation of refractive index with wavelength. Wemple-Di Domenico single oscillator model was applied to determine the optical constants such as oscillator energy E₀ and dispersion energy E_d of the films deposited at different substrate temperatures. The electric free carrier susceptibility and the ratio of the carrier concentration to the effective mass were estimated according to the model of Spitzer and Fan.     

Analysis of polarization dependence for OTDM demultiplexers based on four-wavelength mixing in semiconductor optical amplifier

In optical time-division multiplexing (OTDM) systems using the four-wave mixing (FWM) in a semiconductor optical amplifier (SOA) for time demultiplexing, the polarization states of control pulse and OTDM data lights are an important factor in the optical time demultiplexing process, which can influence the bit error rate (BER) of OTDM systems. In this paper, we analyze the effect of light polarization states on the FWM of a SOA, and use a simulation approach to study the BER performance of 100 Gbit/s OTDM systems that use the FWM in a SOA for optical time demultiplexing. It reveals that the BER or Q factor of OTDM systems is dependent on the misalignment θ between the polarization states of OTDM data and control lights. With increasing θ, both the optical power of resulting FWM component and the BER performance (or Q factor) of OTDM systems is degraded. For linearly polarized lights, our results show that the increase of BER and the reduction in Q factor are made smoothly when θ changes its value from 0° to 75°, whereas the degradation of BER and Q factor becomes rapid when θ exceeds 75°. Although the best system BER is obtained for θ = 0°, the BER performance can still tolerate some misalignment θ (e.g., up to 20° in our simulation). This is useful for the engineering design and applications of SOA-based optical time demultiplexers.     

Elastic scattering of He from Be,B, B,Mg, Mg,Mg and Al

Elastic scattering angular distributions of ³He particles from ⁹Be, ¹⁰B, ¹¹B, ²⁴Mg, ²⁵Mg, ²⁶Mg and ²⁷A1 at E(³He) ≈ 13 to 27 MeV have been measured and some of the representative results are reported. In most cases the angular range of the measured cross sections was from 8° to 150° (lab). The results have been analyzed in terms of a six-parameter optical model and are compared with previous work.     

Interior radiances in optically deep absorbing media—I Exact solutions for one-dimensional model

The exact solutions are obtained for a one-dimensional model of a scattering and absorbing medium. The results are given for both the reflected and transmitted radiance for any arbitrary surface albedo as well as for the interior radiance. These same quantities are calculated by the matrix operator method. The relative error of the solutions is obtained by comparison with the exact solutions as well as by an error analysis of the equations. The importance of an accurate starting value for the reflection and transmission operators is shown. A fourth-order Runge-Kutta method can be used to solve the differential equations satisfied by these operators in order to obtain such accurate starting values. Except for extremely large values of the optical thickness of a layer, the reflection and transmission operators calculated from accurate starting values obtained by the Runge-Kutta method are orders of magnitude (a factor of 10¹¹ better in a typical case at unit optical depth) more accurate than those obtained by the use of the single scattering approximation for an optically thin layer. The relative error in the reflection and transmission operators is less than 10^-12 and 10^-8 respectively up to an optical thickness of 32,768 when calculated by this procedure, while the relative error in the interior radiance is less than 10^-8 at all points within a layer of optical thickness 32,768. It is shown that flux conservation is a poor test of the accuracy of a numerical method, since flux is conserved to all orders for a conservative medium when the doubling method is used, no matter how inaccurate the starting values may be.     

Influence of the interface reflections on the microwave reflection loss for carbonyl iron/paraffin composite backed by a perfect conduction plate

In this work, the influence of interface reflections on the microwave reflection loss (RL) for carbonyl iron/paraffin composite backed by a perfect conduction plate with 30 vol% concentration at various thicknesses was investigated in the 0.1-18 GHz. Using a vector network analyzer, the scattering parameters (S₁₁ and S₂₁) were measured in two different ways. Based on the quarter-wavelength matching model, the results of measurement were analyzed. The experiment shows that there are many minimum values (dips) in RL at various thicknesses when the reflective wave, which is reflected from the absorbing layer and the emerging wave, which is reflected from the backed metal plate are out of phase by 180°, and the peak intensity of the RL is directly affected by the intensity of the reflective wave and the emerging wave. Furthermore, the experiment and numerical calculation demonstrates that the modulus of the normalized input impedance |Z_in/Z₀| equals approximately 1, but the ratio between the modulus of permittivity and permeability |ε/μ| is far from unity at the minimal reflection point.     

Characterization of porous polar semiconductors by their optical spectra in the region of phonon and plasmon-phonon excitations

Optical properties of porous A ³ B ⁵ semiconductors (GaAs, InP, and GaP) in the far-infrared region, in particular, the specular reflection and attenuated total reflection, including the excitation regime of surface polaritons, are considered. Considering a porous material as a composite, we performed calculations in the context of the effective medium model using two modifications of it, Maxwell-Garnett and Bruggeman, which correspond to two different topologies of the composite material—matrix and statistical. The effect of porosity of the material and of such parameters as doping, anisotropy, and penetration depth of an electromagnetic wave to a porous material on optical spectra is analyzed. In addition, some experimental data are presented and the adequacy of the performed numerical simulation is demonstrated.     

Y波导调制器残余强度调制研究

为提高Y波导调制器调制性能从而提高光纤陀螺的整体性能,分析了用于光纤陀螺的Y波导相位调制器残余强度调制产生的机理,即存在波导缺陷以及基底杂散光反射;阐述了残余强度调制对光纤陀螺系统特性的影响,残余强度调制主要影响光纤陀螺的标度因素;测试了不同Y波导残余强度调制的波形特性和它的线性分量及干涉分量大小,不同Y波导残余强度调制大小差异较大,性能好的Y波导残余强度调制大小可以控制在1‰以内;测试了温度对残余强度调制波形特性的影响,残余强度调制受温度影响较大,极端温差下残余强度调制大小波动可达20%;根据残余强度调制的产生机理和线性干涉分量比的大小,提出改进Y波导制作工艺的措施,以期提高Y波导的调制性能。     

Optical-model analysis of elastic scattering of 53.4 MeV helions from Fe

Elastic helion scattering from ⁵⁶Fe at 53.4 MeV was measured over the angular range 12° to 150°. Using the regular optical model, real-potential ambiguities, the shape of the imaginary term and the need for a spin-orbit term were explored. Coupled-channels (SCA) calculations based on the ground state and principal 2⁺ and 3⁻ states indicate that such coupling effects are not as dominant as the inclusion of a spin-orbit potential in the regular optical model. Previously reported helion scattering from ⁵⁹Co and ⁶⁰Ni at 50.1 MeV has been included in an average parameter analysis to generalise the improvements in the helion optical-model parameterization in this energy region.     

高精度干涉式光纤陀螺热漂移分析

为了改进干涉式光纤陀螺的测量精度和温度性能,建立了该仪器输出偏置的解析模型。通过把光纤双折射这一从未被考察过的相位微扰与其它已知误差源进行线性叠加,该模型首次显式地把陀螺性能直接与光纤的力学、光学、热学和几何参数联系起来。利用该模型对常用于10-3 deg/h精度量级光纤陀螺的64层四极对称环圈进行计算,结果表明,保偏光纤所固有的高双折射及其温度涨落对陀螺输出偏置及其热漂移的影响分别在10-3 deg/h和10-2 deg/h量级,而过去研究较多的单模光纤中的舒普效应和热致光弹效应的影响分别在10-4 deg/h和10-3 deg/h量级。该模型表明保偏光纤所固有的高应力双折射是干涉式光纤陀螺的主要误差源,同时较为完备地描述了光纤陀螺中源于光纤性能的误差,也解释了该误差对光纤双折射的非线性依赖。     

Luminescence property of Ce-doped silica decorated with S and Cl anions

Ce³⁺-doped silica was synthesized by sol-gel technique and was further decorated with S²⁻ and Cl⁻ anions through chemical exchange in controlled ambient at elevated temperature. The structure and optical property of samples were examined by X-ray diffraction spectrum, XPS pattern, reflection pattern, and photoluminescence patterns. There is a broad luminescence band at 445 nm under the excitation at 320 nm in the Ce³⁺-doped silica heat-treated in air at 1000 °C. The heat-treatment of the sample in vacuum at 800 °C can increase the intensity of luminescence but have no effect on the wavelength of luminescence. The decoration of S²⁻ and Cl⁻ anions cannot only increase the luminescent intensity but also shift the luminescent wavelength to shorter wavelength.     

The elastic scattering of 33 MeV He particles from Ni,Cu and Zn

Differential cross sections have been measured for the elastic scattering of 33 MeV ³He particles from targets of ^58,60,62,64Ni,^63,65Cu and ^64,66,68Zn over the angular range 5° to 175°. The data have been analysed with the optical model, with particular emphasis on the investigation of the ambiguities in the real potential, the form of the imaginary potential and the use of a spin-orbit term.     

Simulation and analysis of interaction between oblique incidence electromagnetic wave and plasma slab

Numerical simulation of interaction between plasma slab and electromagnetic wave which has different incident frequency and incident angle is discussed in this paper. Some parameters contain reflection coefficient, transmission coefficient, reflectance, transmittance and phase are calculated by transfer matrix method. The relation of these parameters with incident frequency and incident angle is analyzed. The results show that the incident angle has low influence on the parameters when the angle varies from 0° to 30° and from 70° to 90°, but it has high influence on the parameters when it changes from 30° to 70°. These rules have certain directive significance to the research of interaction between oblique incidence electromagnetic wave and plasma slab and to the design of plasma layer.     

Reflector-based phase calibration of ultrasound transducers

Recently, the measurement of phase transfer functions (PTFs) of piezoelectric transducers has received more attention. These PTFs are useful for e.g. coding and interference based imaging methods, and ultrasound contrast microbubble research. Several optical and acoustic methods to measure a transducer’s PTF have been reported in literature. The optical methods require a setup to which not all ultrasound laboratories have access to. The acoustic methods require accurate distance and acoustic wave speed measurements. A small error in these leads to a large error in phase, e.g. an accuracy of 0.1% on an axial distance of 10 cm leads to an uncertainty in the PTF measurement of ±97° at 4 MHz. In this paper we present an acoustic pulse-echo method to measure the PTF of a transducer, which is based on linear wave propagation and only requires an estimate of the wave travel distance and the acoustic wave speed. In our method the transducer is excited by a monofrequency sine burst with a rectangular envelope. The transducer initially vibrates at resonance (transient regime) prior to the forcing frequency response (steady state regime). The PTF value of the system is the difference between the phases deduced from the transient and the steady state regimes. Good agreement, to within 7°, was obtained between KLM simulations and measurements on two transducers in a 1-8 MHz frequency range. The reproducibility of the method was ±10°, with a systematic error of 2° at 1 MHz increasing to 16° at 8 MHz. This work demonstrates that the PTF of a transducer can be measured in a simple laboratory setting.     

Derivation of component aerosol direct radiative forcing at the top of atmosphere for clear-sky oceans

A two-step approach is proposed to derive component aerosol direct radiative forcing (ADRF) at the top of atmosphere (TOA) over global oceans from 60°S to 60°N for clear-sky condition by combining Terra CERES/MODIS-SSF shortwave (SW) flux and aerosol optical thickness (AOT) observations with the fractions of component AOTs from the GSFC/GOCART model. The derived global annual mean component ADRF is +0.08±0.17 W/m² for black carbon, −0.52±0.24 W/m² for organic carbon, −1.10±0.42 W/m² for sulfate, −0.99±0.37 W/m² for dust, −2.44±0.84 W/m² for sea salt, and −4.98±1.67 W/m² for total aerosols. The total ADRF has also been partitioned into anthropogenic and natural components with a value of −1.25±0.43 and −3.73±1.27 W/m², respectively. The major sources of error in the estimates have also been discussed. The analysis adds an alternative technique to narrow the large difference between current model-based and observation-based global estimates of component ADRF by combining the satellite measurement with the model simulation.