光源偏振度对光纤陀螺零漂影响的研究

以Y波导集成光学调制器保偏型干涉式光纤陀螺作为研究对象,根据各光学元器件的参数建立了各器件的琼斯矩阵以及光路传输模型,在此基础上进行了光路偏振误差的理论分析。通过推导,得到了保偏型干涉式光纤陀螺的偏振误差表达式,并首次分析了光源偏振度对光纤陀螺零漂的影响。借助光源尾纤输出的光谱,对由0%~3%之间呈线性变化的偏振度以及对经实验测试的光源偏振度的实际值引起的偏振模式耦合误差的零漂值进行了仿真计算。结果表明,当光路中其它参数不变时,由光源偏振度变化引起的零漂值为0.001°/h,满足了高精度光纤陀螺的精度要求。     

偏振串扰对光纤陀螺零漂及随机游走影响的研究

针对保偏光纤陀螺静态参数受光路偏振串扰误差的影响而使陀螺精度受到制约的问题,从实际应用的角度,研究了保偏光纤陀螺光路中由于各光学器件不理想和熔接点对轴角度误差等因素引起偏振串扰误差的机制。基于琼斯矩阵和相干矩阵,并引入随温度变化的保偏光纤双折射变量,建立了变温环境下保偏光纤陀螺的光路传输模型,对变温环境下偏振串扰误差对保偏光纤陀螺零漂和随机游走的影响进行了理论分析和估算。同时开展了变温环境下光纤环偏振串扰对其静态参数影响的相关实验。实验结果与模型分析结果基本一致,表明该模型是合理的。     

保偏光纤干涉型陀螺的磁场误差分析与抑制方法

基于保偏光纤的琼斯矩阵,建立了保偏光纤线圈的Faraday非互易相移模型,利用该模型进行计算发现:线圈保偏光纤的慢轴与快轴的Faraday非互易相移大小近似相等,但符号相反。并进一步提出了偏振环行干涉型保偏光纤陀螺(PCPM-IFOG),它能使顺时针(CW)和逆时针(CCW)光在保偏光纤线圈中沿慢和快轴分别传输一次,因此顺时针和逆时针光总的Faraday非互易相移等于0,实现了Faraday非互易相移的完全抑制。500m保偏光纤线圈的偏振环行干涉型保偏光纤陀螺的实验结果显示其输出与地球磁场无关,而对于相同传感线圈的干涉型保偏光纤陀螺,当磁场方角发生变化时,陀螺有约±0.3°/h的Faraday零偏漂移。     

高数值孔径双芯光纤的双折射研究

具体分析了具有高数值孔径的双芯光纤的双折射特性。首先利用超格子正交函数法和耦合模理论分析了双芯光纤的几何双折射,并将两种方法计算的几何双折射进行了比较分析。数值计算结果表明双芯光纤在两纤芯非常接近的情况下,几何双折射仍较小,只能到10-5量级。利用超格子正交函数法计算了双椭圆芯光纤的双折射,改变结构参量可使几何双折射达到10-4量级。高的数值孔径需要高的掺锗量,理论上分析了高数值孔径时双芯光纤功率集中区域的应力双折射,应力双折射接近10-4量级。设计制作出了具有良好保偏性能的双芯掺铒光纤,测试、分析了它的几何参量和折射率分布;双芯光纤双折射系数达到了8.4×10-5。双芯掺铒光纤可以作为保偏掺铒光纤,应用到制作具有稳定的单一偏振态输出的光纤激光器。     

干涉式光纤陀螺光路偏振特性的理论分析

首次采用琼斯矩阵建立了消偏型干涉式光纤陀螺完整光路传输系统的数学模型。在此基础上进行了光路偏振特性的理论分析,讨论了各器件的性能对陀螺偏振噪声的影响,分析了光纤消偏器的消偏作用。通过分析计算,得到了消偏型干涉式光纤陀螺的最大偏振误差表达式。在不同精度级别的消偏型光纤陀螺中,计算出了光纤消偏器应该达到的精度要求,为今后减小零漂打下了理论基础。     

对轴误差对光纤陀螺输出的影响

理论分析并试验研究了Y波导保偏尾纤与保偏光纤线圈之间熔接点的对轴误差对光纤陀螺输出的影响.根据简化的光纤陀螺光路误差模型,对光纤陀螺的输出相位误差与光路中主要耦合点的对轴误差的关系进行了理论推导和仿真分析,并利用一个实际的闭环光纤陀螺试验研究了主要熔接点的对轴误差变化对光纤陀螺零偏和零偏稳定性的影响.结果表明,Y波导保偏尾纤与保偏光纤线圈之间的对轴误差是引起光纤陀螺输出误差的重要因素,必须尽量减小.     

干涉式光纤陀螺光路系统的物理模型

光路系统的偏振误差极大地制约着光纤陀螺精度的提高。利用相干矩阵和琼斯矩阵对光纤陀螺中光学器件和熔接点的光学参数进行描述,建立了干涉式光纤陀螺光路系统的物理模型。与之前相关文献报道相比,该模型所表达的光路系统更加接近于工程实际。在此基础上,提出一种分析光学器件和熔接点缺陷,以及光路损耗对光纤陀螺偏振误差影响的新方法。该方法可以有效地分析光路系统缺陷对零偏和标度因数的影响,在工程上可作为评价干涉式光纤陀螺光路系统性能的一个途径。     

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/℃.     

偏光干涉对光纤陀螺性能的影响

从光纤陀螺光学系统缺陷角度,研究了由于光纤陀螺保偏光纤融接误差及光学器件的不完善引起的偏光干涉效应,理论分析并实验研究了偏光干涉效应对传输光谱的影响及其对光纤陀螺性能的影响。研究表明,在当前的技术条件下,偏光干涉效应对光纤陀螺的标度因数影响可以忽略,偏光干涉不影响一般意义下的光源相干长度,但是却导致光源相干特性的变化,反应在相干图上出现了多个干涉衬比度峰值,这会降低宽谱光源的短相干长度特性给光纤陀螺带来的好处,由此也说明不能仅由相干长度这一个参量描述光源的相干特性。     

基于多模干涉滤波器和双折射滤波器的四波长可开关光纤激光器

设计了一种基于多模干涉滤波器和双折射滤波器的四波长可开关光纤激光器,理论分析了多模干涉滤波器和双折射滤波器及其级联结构的滤波特性.双折射滤波器能有效地抑制多模干涉滤波器的不规则边模.保偏掺铒光纤同时作为增益介质和滤波元件,优化多模光纤长度和保偏掺铒光纤长度保证了波长间隔的最佳匹配,级联滤波器的滤波周期为4.89 nm.调节偏振控制器,光纤激光器实现了单波长、双波长、三波长以及四波长可开关激光输出,输出激光的边模抑制比均大于40 dB,1h内波长波动均小于0.1 nm.     

Optically compensated dual-polarization interferometric fiber-optic gyroscope

We first introduce optical compensation into the field of interferometric fiber-optic gyroscopes (IFOGs), using the opposite polarity of the disturbance between two orthogonal polarization states to suppress polarization-fluctuation-induced noise. A dual-polarized IFOG, in which the fast and slow axes of polarization-maintaining fiber work simultaneously, is implemented and tested. Interference signals of the two axes are added to achieve optical compensation. Experiments show that the IFOG's sensitivity is effectively enhanced in compensated output: all Allan variance indices are improved, among which bias instability is reduced from 0.335 and 0.227 deg/h(fast and slow axes output, respectively) to 0.061 deg/h.     

Analysis of bias thermal stability of interferometer fiber-optic gyroscope using a solid-core polarization-maintaining photonic crystal fiber

Bias thermal stability of a fiber-optic gyroscope using polarization-maintaining photonic crystal (PM-PCF) was studied. The thermal sensitivity of birefringence in PM-PCF and polarization cross talking in fiber coil was measured. Using an OCDP method, the polarization cross talking causing phase error of the fiber-optic gyroscope (FOG) was analyzed. The contrast experiment result of the FOGs with the PM-PCF coil and PMF coil showed that using PM-PCF instead of PMF can improve the FOG’s bias thermal stability by about 50 %.     

Development of high grade fiber-optic gyroscopes

Tokimec has been developing high grade interferometric fiber-optic gyroscopes (I-FOGs) for useful applications. The I-FOG consists of a sensing coil module, a light emitting module and an electronics circuits module. We achieved the bias stability of 0.003 deg/h and the angular random walk of 0.001 deg/√h and the scale factor error of 10 ppm (1σ). Then the azimuth error of the strapdown gyrocompass system with the high grade I-FOGs was less than ±0.05 s λ (deg) under the environmental temperature condition 23±5(°C).     

Design and analysis of a photonic crystal fiber with four-hole unit

A novel photonic crystal fiber (PCF) based on a four-hole unit is proposed in order to meet the requirements of high birefringence, negative dispersion and confinement loss in fiber-optic communication. The proposed design has been simulated based on the full vector finite element method (FVFEM) and anisotropic perfectly matched layers (APML). Analysis results show that the proposed PCF can achieve a high birefringence to the order of 10⁻² at the wavelength of 1.55 μm, a large negative dispersion over a wide wavelength range and confinement losses lower than 10⁻⁹ dB/m simultaneously, which has important applications in polarization-maintaining (PM) fibers, single-polarization single-mode (SPSM) fibers, dispersion compensation fibers and so on.     

Thermal analysis of the effects of thermally induced nonreciprocity in fiber optic gyroscope sensing coils

The response of interferometric fiber optic gyroscope sensing coils to a time-varying, radial thermally induced nonreciprocity is investigated. Sensing coils wind with polarization-maintaining fibers in quadrupolar wind configurations developed in our study examining the effect of radial thermal gradients are used with experimental setup. Induced gyroscope bias drift, measured as a function of temperature and time, is compensated for quadrupolar winding configurations using our model. Our results show that thermally induced nonreciprocity can be calculated with the same coefficient in difference temperature changing conditions using our model.     

多维温度场对光纤环Shupe效应误差影响的理论分析

光纤环作为干涉型光纤陀螺的核心敏感元件,易受时变温度环境引起的Shupe非互易性相移的影响,进而严重降低对于惯性空间转动的测量精度.本文推导了目前广泛应用的四极绕法光纤环的温度效应误差模型,分析了沿光纤环径向、轴向与圆周方向多维温度场对于零偏漂移的影响机理并进行了仿真验证.研究结果表明,径向与轴向的瞬态温场引起的零偏误差正比于光纤环各层外内壁温变速率之差的加权和,并且随着接近光纤进出的顶层,其所占份额将线性增大.圆周方向的零偏误差则取决于光纤进出端与长度中点连线两侧温变速率空间分布的对称性,并且当不均匀的温度场分布远离进出端时,其影响将减小.以上发现可为复杂温度环境下工作的陀螺仪表与惯性导航系统的热结构设计提供理论指导与工程参考.     

光纤陀螺受辐照影响机理分析

构成光纤陀螺敏感器件的保偏光纤环在辐射环境中损耗会增加,陀螺的精度随之降低,从而限制了光纤陀螺在空间中的应用。采用60Co作为辐射源模拟空间辐射环境,对光纤陀螺及其光电器件进行了大量的试验,并对光纤陀螺及其光电器件受空间辐射影响的机理进行了研究,得出光纤陀螺光电器件中保偏光纤环受辐射影响最严重,从而重点分析了光纤陀螺敏感器件保偏光纤环的辐射影响机理,从原理上探讨了保偏光纤环在辐射条件下损耗的增加对光纤陀螺的影响,为光纤陀螺抗辐射加固技术提供了理论基础。     

高折射率椭圆芯布拉格光纤的偏振特性

应用带完全匹配层边界条件的全矢量有限元方法,分析了高折射率椭圆芯布拉格光纤的偏振特性,详细讨论了光纤结构参量对模式双折射度以及群速度走离的影响,结果发现:高折射率椭圆芯布拉格光纤的模式双折射度可达10-2量级,比传统保偏光纤至少高出一个量级,并且表现出不同于传统保偏光纤的群速度走离特性;在保持较高双折射度的同时,通过合理的结构设计,可在一定的波长处灵活地获得较大的群速度走离或零走离特性,具有重要的潜在应用价值;最后,简要分析了低折射率区域的折射率变化对偏振特性的影响;研究结果有助于设计高性能的微结构保偏光纤。     

Single-mode fiber gyroscope with three depolarizers

In this letter we present a single-mode fiber gyroscope (FOG) with low long-term drift. Only single-mode fiber components except for three fiber depolarizers were used. A simplified mathematic model has been proposed to explain the bias stability of the gyro. Several open-loop and closed-loop FOGs with 0.1–0.5°/h drift have been demonstrated.     

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.