Effect of radiation-induced mean wavelength shift in optical fibers on the scale factor of interferometric fiber optic gyroscope at a wavelength of 1300 nm

In order to analyze the effect of wavelength-dependent radiation-induced attenuation (RIA) on the mean transmission wavelength in optical fiber and the scale factor of interferometric fiber optic gyroscopes (IFOGs), three types of polarization-maintaining (PM) fibers is tested by using a ⁶⁰Co γ -radiation source. The observed different mean wavelength shift (MWS) behaviors for different fibers are interpreted by color-center theory involving dose rate-dependent absorption bands in ultraviolet and visible range and total dose-dependent near infrared absorption bands. To evaluate the mean wavelength variation in fiber coil and the induced scale factor change for space-borne IFOG under low radiation dose in space environment, the influence of dose rate on the mean wavelength is investigated by testing four germanium (Ge) doped fibers and two germanium-phosphorus (Ge-P) codoped fibers irradiated at different dose rates. Experimental results indicate that the Ge-doped fibers show the least mean wavelength shift during irradiation and their mean wavelength of optical signal transmitting in fibers will shift to shorter wavelength in low-dose-rate radiation environment. Finally, the change in the scale factor of IFOG resulting from the mean wavelength shift is estimated and tested, and it is found that the significant radiation-induced scale factor variation must be considered during the design of space-borne IFOG.     

Effect of radiation-induced mean wavelength shift in optical fibers on the scale factor of an interferometric fiber optic gyroscope at a wavelength of 1300 nm

In order to analyze the effect of wavelength-dependent radiation-induced attenuation (RIA) on the mean trans- mission wavelength in optical fiber and the scale factor of interferometric fiber optic gyroscopes (IFOGs), three types of polarization-maintaining (PM) fibers are tested by using a 60 Co γ-radiation source. The observed different mean wave- length shift (MWS) behaviors for different fibers are interpreted by color-center theory involving dose rate-dependent absorption bands in ultraviolet and visible ranges and total dose-dependent near-infrared absorption bands. To evaluate the mean wavelength variation in a fiber coil and the induced scale factor change for space-borne IFOGs under low radiation doses in a space environment, the influence of dose rate on the mean wavelength is investigated by testing four germanium (Ge) doped fibers and two germanium-phosphorus (Ge-P) codoped fibers irradiated at different dose rates. Experimental results indicate that the Ge-doped fibers show the least mean wavelength shift during irradiation and their mean wavelength of optical signal transmission in fibers will shift to a shorter wavelength in a low-dose-rate radiation environment. Finally, the change in the scale factor of IFOG resulting from the mean wavelength shift is estimated and tested, and it is found that the significant radiation-induced scale factor variation must be considered during the design of space-borne IFOGs.     

Effect of spectral dependencies of radiation-induced attenuation in polarization maintaining fibers on interferometric fiber optic gyroscope at near-infrared wavelengths

In order to analyze the effect of spectral dependencies of radiation-induced attenuation in polarization maintaining fibers on interferometric fiber optic gyroscopes at near-infrared wavelengths, phosphorus-doped, germanium-doped and pure-silica-core fibers were exposed to a ⁶⁰Co γ-radiation source, as well as their spectral properties were compared and interpreted by color centers theory involving total dose-dependent infrared absorption bands. Based on testing and comparing the radiation-induced attenuation spectra, the loss variation and mean wavelength shift in fibers at 1300 nm and 1550 nm wavelengths are discussed. Finally, the random walk coefficient degradation and scale factor error induced by spectral dependencies of radiation-induced attenuation in fibers are verified.     

干涉式光纤陀螺中的Rayleigh散射研究

从光的干涉原理出发分析了Rayleigh背向散射对干涉式光纤陀螺性能的影响,得出了散射光强与光纤位置之间的关系式,绘制了散射光强与光纤中位置之间的关系曲线,得到了距离光纤的两个端点越远Rayleigh背向散射对光纤陀螺的性能影响越小的结论。研究结果对分析光纤陀螺的光路误差有一定的参考价值。     

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。     

Radiation-induced attenuation self-compensating effect in super-fluorescent fiber source

The compact super-fluorescent fiber source(SFS) output spectra variations at different pump currents and under different dose of gamma-ray radiation were measured and compared respectively. The radiation-induced attenuation(RIA)self-compensating effect in SFS based on photo-bleaching was found and the general mathematic model of SFS output spectra variations was made. The radiation-induced background attenuation(RIBA) at the pump wavelength was identified to be the main cause of the total output power and spectra variations and the variations can then be compensated by active control of the pump power to enhance the self-compensating effect. With closed-loop feedback control of pump current,double-pass backward(DPB) configuration and spectrum re-shaping technology, an SFS prototype was made and tested.The mean-wavelength stability of about 87.4 ppm and output power instability of less than 5% were achieved under up to200 krad(Si) gamma-ray irradiation.     

脉冲γ射线对光纤的辐射效应

介绍了光纤的损耗机制和γ射线对光纤的辐射效应,设计了针对脉冲γ射线作用于光纤而产生辐射感生损耗的实验测量系统。利用平均光子能量为0.3 MeV、脉冲宽度25 ns、剂量率2.03×107Gy.s-1,和平均光子能量为1.0 MeV、脉冲宽度25 ns、剂量率5.32×109Gy.s-1的2种脉冲γ射线分别作用于多模和单模光纤,分别采用波长为405,660,850,1 310和1 550 nm的激光光纤传输系统对辐射感生损耗进行了测量。获得了光纤辐射感生损耗和辐射剂量的关系,并对实验结果进行分析。从实验结果可以看出:在近红外到可见光范围内,脉冲γ射线对光纤作用产生的辐射感生损耗随探测波长减小而增大;在0.1~3.5 Gy剂量范围内,多模光纤辐射感生损耗和辐射剂量呈线性关系。分析辐射对光纤的作用机制和实验结果后得出:光纤基质原子的电子能级对传输光子的共振吸收而造成吸收损耗增加;光纤折射率分布的改变从而导致波导损耗增加。     

光纤陀螺惯导系统航位推算误差补偿方法研究

 针对惯导系统定位误差随时间积累而增大的缺点,提出利用航位推算方法进行误差补偿。在航位推算中根据引起误差的主要因素推导出位置误差方程,以此方程为依据,建立相应的卡尔曼滤波器。将惯导系统速度与航位推算速度之差作为滤波器的输入,估计系统的姿态、速度、位置及里程计刻度系数误差值,并通过闭环反馈进行实时误差补偿修正。任选2条非闭合路径进行跑车实验,第一条路径定位误差补偿修正前是3.49‰,补偿修正后定位误差是2.3‰,第二条路径补偿修正前定位误差是2.4‰,补偿修正后定位误差是2‰。实验结果表明：采用航位推算误差补偿方法可以有效降低系统定位误差。     

脉冲γ射线对光纤的辐射效应

介绍了光纤的损耗机制和γ射线对光纤的辐射效应,设计了针对脉冲γ射线作用于光纤而产生辐射感生损耗的实验测量系统。利用平均光子能量为0.3 MeV、脉冲宽度25 ns、剂量率2.03×107 Gy·s-1,和平均光子能量为1.0 MeV、脉冲宽度25 ns、剂量率5.32×109 Gy·s-1的2种脉冲γ射线分别作用于多模和单模光纤,分别采用波长为405,660,850,1 310和1 550 nm的激光光纤传输系统对辐射感生损耗进行了测量。获得了光纤辐射感生损耗和辐射剂量的关系,并对实验结果进行分析。从实验结果可以看出：在近红外到可见光范围内,脉冲γ射线对光纤作用产生的辐射感生损耗随探测波长减小而增大;在0.1~3.5 Gy剂量范围内,多模光纤辐射感生损耗和辐射剂量呈线性关系。分析辐射对光纤的作用机制和实验结果后得出：光纤基质原子的电子能级对传输光子的共振吸收而造成吸收损耗增加;光纤折射率分布的改变从而导致波导损耗增加。     

Effect of launching condition in response time analysis for few selected tapered porous clad optical fiber gas sensors

In this paper, the effect of launching condition of light and the geometry of the sensing region in the case of detection of gases using attenuated total internal reflection (ATR) technique in multimode step index tapered fiber has been described. Using ray approach the response time of the sensor in case of parabolic, linear and exponential-linear tapered optical fiber have been carried out. It has been shown that launching condition and geometry of the sensing region effect the sensitivity of the sensor. Out of three designs the sensor having exponential-linear tapered with selected ray launching has maximum sensitivity and low response time of the sensor.     

Study of reflection error in closed-loop polarization-maintained interferometric fiber optic gyroscope

To analyze quantitatively and systematically the reflection error in optical path of closed-loop polarization-maintained (PM) fiber optical gyroscope (FOG), the optical model is established and analyzed. Based on the optical model and the principle of the coherence detection in signal processing, the source of the reflection error is disclosed from the point of wave trains, and its effect on FOG performance is analyzed in detail, including variation as the step wave on modulator and as the environment temperature. In addition, the measures are promoted to suppress the reflection error, and the simulation result demonstrates that the peak-to-peak value of the reflection error can be suppressed from about 0.8°/h to less than 6×10⁻³°/h through matching the length of birefringent pigtails, which is small enough to meet the requirement of FOG with high performance.     

基于小波-ARMA模型的光纤陀螺自适应滤波

针对光纤陀螺输出是非平稳信号的特点,提出了小波-ARMA模型建模方法 ,并与ARIMA模型进行了对比分析;针对滤波方程中的量测噪声不能确定的问题,提出了基于量测噪声自适应的滤波方法,并与卡尔曼滤波进行了对比分析。研究结果表明:滤波方法相同时,小波-ARMA模型的滤波效果优于ARIMA模型;模型相同时,自适应滤波效果优于卡尔曼滤波;且建模精度大于滤波方法对滤波效果的影响。Allan方差分析表明:基于小波-ARMA模型的自适应滤波能很好地滤除光纤陀螺中的量化噪声,提高陀螺的输出精度。     

谐振型光纤陀螺方波频率调制方法

分析了谐振型光纤陀螺(R FOG)方波频率调制方法的工作原理和调制性能,得到了采用方波频率调制时R_FOG的极限灵敏度,并对方波频率调制和正弦频率调制两类调制方法的特性进行了比较。结果表明,方波调制方法的极限灵敏度优于正弦频率调制方法的极限灵敏度,其输出信号为方波强度调制信号,易于与I_FOG中类似的数字解调方法相结合,是实现全数字处理R_FOG的较理想的调制方案。     

基于光谱吸收型光纤传感器的煤矿瓦斯测量技术

甲烷是瓦斯的主要成分,是易燃易爆的气体。介绍了瓦斯的光谱特性以及光谱吸收法测量甲烷气体浓度的原理,给出了光谱吸收型光纤瓦斯气体传感器的主要进展和技术路径,包括差分吸收测量法和谐波吸收测量法。通过分析可看出,光谱吸收型光纤瓦斯传感器以其优良的特性得到了广泛关注,其中差分吸收法的抗干扰能力强,系统可靠性高,具有较强的工程应用价值。     

损耗可控条件下掺铒光纤中光速减慢现象的研究

由于相干布居振荡效应,光脉冲通过处于吸收状态的掺铒光纤介质时,将导致群速度传输减慢. 由掺铒光纤的吸收特性可知,此时必伴随着强烈的吸收损耗,这势必会给实际的慢光信号测量及光通信领域带来诸多的困难. 从铒离子基态粒子速率方程出发,对损耗可控条件下的光速减慢传输进行了数值仿真研究,并加以实验验证. 研究表明：抽运光强度越高,信号光损耗系数越小;抽运掺铒光纤长度越长,信号光损耗系数越小. 通过优化抽运光强度、掺铒光纤长度等参量,可以实现损耗可控条件下的光脉冲群速度减慢传输. 关键词： 时间延迟 吸收损耗 掺铒光纤     

机载光电系统中光纤陀螺卡尔曼滤波方法应用

针对光纤陀螺输出噪声大、随机漂移难抑制,从而影响机载光电系统低频性能的问题,分析了系统中光纤陀螺输出的实测数据,根据其噪声特性建立了光纤陀螺噪声的AR2 模型。研究了基于卡尔曼滤波的光纤陀螺在机载光电系统中的应用方法。对比传统应用的滑动平均滤波,给出实验结果。结果表明:卡尔曼滤波能有效消除陀螺高频噪声,抑制系统的随机漂移,在一定程度上能够提高系统的低频工作性能。研究结果对机载系统中光纤陀螺的应用有较好的参考价值。     

基于全息光学元件的光纤光谱仪的光路设计

基于全息光学理论分析了全息光学元件的高斯成像性质,包括光焦度、成像位置、衍射效率以及作为光纤光谱仪光栅元件的可行性,并以全息光栅的成像理论以及光谱仪工作原理为基础,设计了光谱仪器光学系统的各个参数,通过Zemax软件的仿真、像质评价及优化,得出最终的参数和模拟结果。所使用的全息光栅记录波长为575 nm,记录光束之间的夹角为10,一束为平面波,一束为球面波,焦距40 mm,使用+1级衍射光,光栅孔径为10 mm。光谱仪的工作波长范围为400 nm～800 nm,体积140 mm*30 mm*40 mm,谱面展宽29.1 mm。通过在光学平台上搭建光路,利用已研发完成的电路系统及光谱仪软件,针对汞灯光谱进行了试验,光谱分辨率优于8 nm,测量得到的汞灯光谱与标准汞灯光谱一致,表明了所设计的基于全息元件的光纤光谱仪光学系统是可行的。     

光纤传感颜色识别系统的设计与实现

利用光电传感技术进行颜色识别可以克服传统识别方法的许多不足,能辨别出微小的颜色变化并大幅度提高测试精确度。通过探测物体的后向反射光,一种采用反射式数字光纤传感器设计的颜色识别系统得以实现。由于不同颜色的被测物体对光信号吸收和反射能力不同,它可以根据反射光的强弱来识别颜色。实验证明采用光纤传感器可以实现近距离范围内对被测物体任意区域的非接触式测量,测量范围宽、测试精度高,在表面探测中具有很好的应用前景。     

球形光纤端面效应及其应用

本文介绍了球形光纤端面的制作方法,采用射线理论和等效透镜法分析了圆球形端面多模光纤的端面效应,并给出了两个不同端面多模光纤之间耦合的实验结果。结果表明：圆球形端面光纤具有聚光特性,与平端面相比,使用圆球形端面光纤不仅可以提高光器件之间的耦合效率,而且增大了它们之间的耦合距离,利于光路调试;可广泛应用于光源与光纤、光纤与光纤、光纤与探测器之间的耦合。     

A novel photonic crystal fiber with near-circular mode field distribution for the application of fiber optic gyroscope

In this letter, we reported on a polarization-maintaining photonic crystal fiber (PM-PCF) with near-circular mode field distribution. The modal field distribution of the proposed PM-PCF is near-circular, which enhanced the mode field compatibility between PM-PCFs and traditional polarization-maintaining fibers (PMFs). And the birefringence of the novel PM-PCF can easily achieve the order of 10⁻³–10⁻², which is at least 1–2 order of magnitude higher than that of commonly used Panda or Bow-tie PMFs. Additionally, the diameter of this PM-PCF is much smaller than traditional PM-PCFs. It can well satisfy the application of fiber optic gyroscope (FOG) which need high polarization-maintaining, high-precision and miniaturization.