基于光纤陀螺的教学实验寻北仪

光纤陀螺可测量沿其轴向转动角速度,利用此功能通过四位置法可以实现寻北、实验室所在纬度以及地球自转角速度的测量.本文介绍光纤陀螺寻北仪和四位置法的工作原理.另外还介绍了寻北仪的实验装置和基本操作过程,以及对数据的处理方法.     

光纤陀螺

1 前言光纤陀螺是利用Sagnac效应检测旋转角速度的一种光纤传感器。由于光纤陀螺(OFG)具有表1所列的许多特征,因此各国都在积极研究开发下一代陀螺。本文主要介绍OFG的原理、结构及其应用。     

基于单模光纤的交叉相位调制型频率分辨光学开关超短脉冲测量

利用单模光纤中的光弹效应和交叉相位调制(XPM)效应,提出了一种频率分辨光学开关法测量超短脉冲的新方案.在本方案中,单模光纤的前一部分产生可变延迟,后一部分作为非线性介质产生非线性效应.该方案只需一根单模光纤,无须复杂的光路校准,结构简单,损耗低;光纤中的XPM效应易发生,无须相位匹配.对提出的方案进行了数值模拟,采用基于矩阵的主元素广义投影算法,恢复出待测脉冲的幅度和相位信息,并研究了光纤长度和待测超短脉冲的脉冲宽度对测量结果的影响.结果表明:测量准确度随着光纤长度的增加而提高,选取长度为2 km的光纤,就可以实现对超短脉冲的准确测量;本文方案适用于脉冲宽度不小于80 fs的超短光脉冲的测量.     

基于深度学习的光纤超短脉冲啁啾放大研究

全光纤超短脉冲啁啾放大技术在激光技术和超快光学领域备受关注。针对传统数值方法分析光纤中超短脉冲啁啾放大过程存在计算量大、效率低等问题,采用深度学习方法开展全光纤超短脉冲啁啾放大过程建模研究。首先分析脉冲啁啾参量等参数对超短光脉冲传输过程的影响。预训练设计的深度神经网络模型,分析网络对不同初始脉冲啁啾参量的预测精度,进一步探索了不同初始脉冲半峰全宽、峰值功率和啁啾参量等复杂情况下网络的泛化性及预测精度。本研究拓宽了数据驱动方法在激光行为预测方面的应用,为光纤中超短脉冲的特性研究提供了新思路。     

掺铒光纤环镜中超短光孤子的放大与压缩I．基本原理

用常规掺铒光纤放大器放大超短光孤子存在一个重大困难。就是在放大过程中光纤非线性效应会引起孤子波形及频谱畸变，使得输出脉冲不再具有孤子特性，从而影响系统性能。提出一种利用掺铒光纤环镜放大超短光孤子的新方法，数值计算表明，该方法不仅可实现无畸变的光孤子放大，而且能同时实现孤子宽度的有效压缩。当宽度为2ps的基阶孤子经过长度为92．6m、增益为14．4dB的环镜后，其峰值功率被放大165倍，脉冲宽度被压缩到0．19ps，时间一带宽积为0．303。脉座能量仅占整个脉冲能量的3．8％，表明由环镜输出的放大脉冲很大程度上具有基阶孤子特性。     

1GHz,48.8fs高重复频率掺镱光纤飞秒激光器研究

GHz基本重复频率光纤超短脉冲激光器由于具有宽光谱,窄脉宽等优势,在高速光刻,高端制造,天文探测,太赫兹检测,精密仪器等领域应用广泛。然而在实现1GHz以上基本重复频率锁模的前提下,如何输出脉冲宽度在50fs以下的超短脉冲是当前科学研究的难点。文章以实现更宽光谱,更窄脉宽的GHz重复频率光纤超短脉冲激光器为目标,通过非线性偏振旋转锁模(NPR)技术,利用波分复用光纤准直器(WDM-Collimator)缩短激光谐振腔长度,最终实现了48.8fs脉冲宽度的1GHz基本重复频率光纤激光器。该脉冲宽度是当前国际上1μm波段GHz基本重复频率光纤激光器的最窄直接输出脉冲宽度。最后对激光器集成形成样机,并有效降低制造成本,提升了系统稳定性。该激光样机可满足天文光梳、卫星导航等领域空间尺寸的需求,有望推动高重复频率光纤超短脉冲激光器工业化、商业化发展。     

超短脉冲光纤激光器新进展及其应用

超短脉冲光纤激光器是目前激光技术研究领域中最具有活力的研究课题．有着巨大的应用前景。本文介绍超短脉冲光纤激光器的发展概况及最新进展，论述掺稀土超短脉冲光纤激光器原理，对其关键技术及多种新型技术方案做了介绍和比较，分析超短脉冲激光器的应用前景及发展趋势。     

迈克尔逊干涉在超短脉冲测量中的应用

分析了迈克尔逊干涉仪用于强度自相关测量超短脉冲的原理,设计了非共线结构迈克尔逊干涉仪,并利用二次谐波晶体对超短脉冲的强度自相关过程进行分辨,实现对超短脉冲的测量。     

光纤光栅中孤子时延特性研究

从光纤光栅慢光产生的物理机理和非线性耦合模方程组,仿真分析了均匀布拉格光栅中光栅孤子传输时的减速特性;利用高速示波器搭建了测量高能量、窄脉冲通过布拉格光纤光栅后时延特性的实验系统,分别测量了由普通单模光纤和高非线性光纤制作的均匀光栅对光脉冲的时延特性.实验结果为:用5 cm长普通单模光纤制作的布拉格光栅可以使在其中传输...     

VUV超短脉冲的产生及其在超快动力学中的应用

真空紫外超短脉冲激光具有波长短、单光子能量高、脉宽小等特点,在飞秒化学以及超快动力学等方面具有相当广泛的应用前景.由于直接利用受激辐射获得真空紫外超短脉冲是相当困难,因此利用非线性频率转换技术,超短脉冲与惰性气体相互作用,将红外、可见或紫外光波段的超短脉冲转换到真空紫外波段是目前获得紫外超短脉冲最快捷有效的方式.围绕真空紫外超短脉冲的产生及其在超短动力学中应用展开,介绍了产生真空紫外超短脉冲的高斯谐波、空心光纤四波混频和光丝四波混频的方法,对其优缺点作了评述,并对真空紫外超短脉冲激光在超快动力学过程中的应用进行了简单的总结.     

一种新的光电设备方位角度检测方法

针对工作在静座桅杆条件下的光电设备,提出一种低成本的方位角度检测方法。采用2个倾角仪检测光电设备的俯仰轴和倾斜轴的角速度,用1个陀螺检测光电设备的方位轴角速度,完成光电设备方位角度变化量的解算。在已知初始方位角度的情况下,获取光电设备的实时方位角度值。实验表明,采用0.01的倾角仪和零偏稳定性为0.015/h的激光陀螺,方位精度达到0.009。     

Electrical crosstalk-coupling measurement and analysis for digital closed loop fibre optic gyro

The phase modulation and the closed-loop controller can generate electrical crosstalk-coupling in digital closed-loop fibre optic gyro. Four electrical cross-coupling paths are verified by the open-loop testing approach. It is found the variation of ramp amplitude will lead to the alternation of gyro bias. The amplitude and the phase parameters of the electrical crosstalk signal are measured by lock-in amplifier, and the variation of gyro bias is confirmed to be caused by the alternation of phase according to the amplitude of the ramp. A digital closed-loop fibre optic gyro electrical crosstalk-coupling model is built by approximating the electrical cross-coupling paths as a proportion and integration segment. The results of simulation and experiment show that the modulation signal electrical crosstalk-coupling can cause the dead zone of the gyro when a small angular velocity is inputted, and it could also lead to a periodic vibration of the bias error of the gyro when a large angular velocity is inputted.     

Compliant structures with time-varying moment of inertia and non-zero averaged momentum and their application in angular rate microsensors

In this work we introduce a new class of fully compliant structures performing vibratory motion, yet characterized by non-zero averaged momentum, appearing due to time-dependency of the inertial parameters. The work is motivated by microelectromechancial systems (MEMS) applications, where an implementation of unidirectional, non-vibratory motion involving relative motion of parts is not desirable for reliability reasons. Instead of changing the mass, which is challenging on the microscale, the moment of inertia of the proof mass performing tilting vibrations is controlled in such a way that it is higher or lower depending on the sign of the velocity. This results in a non-zero angular momentum averaged over the period. The equations describing the dynamics of a generic structure with a time-varying inertia and in a rotating coordinate frame are derived by using a variational principle. Simple approximate expressions for the averaged momentum and steady tilting angle are obtained and validated numerically. Based on the model results for different operational scenarios, we demonstrate that these devices can be efficiently used in fully compliant actuators and vibratory angular rate sensors (microgyros) with a steady response in a sensing mode (“pseudospinning disk gyros”), as well as in a parametrically excited gyro. The structure can be viewed also as a first step toward the realization of dynamic materials (DM) which are substances with material properties that may change in space and time.     

Generation of a large orbital angular momentum beam via an optical fiber winding around a curved path and its application

Many papers have been published on the study of orbital angular momentum(OAM) of the laser modes based on the Laguerre–Gaussian(LG) beam and helical phase plate or rotating cylindrical lens, and the principal ray of the LG beam remains straight line. These ways are difficult to get a large OAM modes. In this paper, we propose a novel method to prepare a large OAM modes when the light propagates through a optical fiber winding around a curved path, and establish a theoretical framework based on the principal ray path changing. Firstly, we investigate three kinds of winding structure.Secondly, based on the analytical solutions and numerical calculations, we can find that the spiral body can achieve a large OAM temporal pulse. At the same time, based on the zero OAM diffraction diagram, we can obtain an improvement of resolving power beyond Rayleigh's criterion. Finally, applying a large OAM diffraction pattern to realize 12-bitencodes,we can obtain a high-security optical information transfer system.     

MEMS陀螺随机误差特性研究及补偿

为了提高MEMS陀螺输出角速度的精度,采用Allan分析法以及Kalman滤波算法对MEMS陀螺仪进行随机误差分析和补偿。由Allan方差分析陀螺的输出数据,对Allan方差进行最小二乘法拟合,得到各项随机噪声的定量评价指标;对陀螺的输出数据使用AR模型进行数学建模,采用AIC准则确定了AR模型的阶次,建立了陀螺零漂数据的离散时间表达式;在AR模型所建立的陀螺随机误差模型的基础上,设计了Kalman滤波器,对陀螺输出数据使用Kalman算法进行了滤波处理,对陀螺的随机误差进行了补偿;通过Allan方差对Kalman算法对陀螺随机误差的补偿效果进行分析。实验结果表明:角速率随机游走Kalman滤波前为槡0.148 7°/h~(1/2),Kalman滤波补偿后为槡0.004 1°/h~(1/2),,通过补偿可减小97.24%的角速率随机游走误差;零偏不稳定性Kalman滤波前为1.940 8°/h,Kalman滤波补偿后为0.054 2°/h,通过补偿可减小97.21%的零偏不稳定性误差;速率随机游走Kalman滤波前为2.698 5°/h~(3/2),Kalman滤波补偿后为0.334 3°/h~(3/2),通过补偿可减小87.61%的速率随机游走误差。Kalman滤波适用于MEMS陀螺的滤波处理,可有效降低陀螺的随机误差。     

基于自发辐射光谱的超声速流场测速技术

等离子体状态参数测量是研究等离子体特性,开展等离子体模拟再入环境、等离子体隐身、等离子体减阻以及边界层控制等研究的重要基础。利用等离子体射流的自发辐射光谱,提出了一种基于光学多普勒频移效应的等离子体超声速射流测速的方法。首先,测量了等离子体中Ar原子产生的自发辐射光谱,选择696.54 nm的特征谱线,作为等离子体发生器测速实验的运动光源;其次,使用光谱仪、传能光纤、EMCCD相机和高光谱分辨法布里-珀罗（F-P）干涉仪,设计了高温等离子体速度测量光路;最后,在氩壁稳电弧等离子体发生器上,开展了超声速射流速度测量实验。实验中,同一测点的Ar原子产生的自发辐射光谱,分别被与等离子体射流运动方向成49°和90°夹角的收集透镜收集进入光谱仪,经光谱仪分光后仅保留特征谱线696.54 nm附近自发辐射光进入传能光纤,从而消除其他波长的自发辐射光的影响;光谱仪输出的特征辐射光谱,经光纤传输及透镜整形成平行光后,精细度30、自由光谱范围6.6 GHz的F-P干涉仪,形成多光束干涉圆环,并由EMCCD相机采集,实现对特征谱线的超高精度分辨;根据多普勒原理,不同角度收集的同一测点处Ar 696.54 nm特征谱线的频移将有所不同,EMCCD采集的干涉圆环半径也将不同,通过测量同一级次不同收集方向特征谱线形成的干涉圆环半径改变量,可测得高温等离子体射流流动速度。针对同一喷管开展了两车对比试验,实验测得两车射流轴向速度分别为791和783 m·s-1,具有较好的重复性。结果表明基于多普勒效应,利用高温气体自发辐射光谱,结合高光谱分辨F-P干涉仪,能够实现高温等离子体射流速度的精确测量,该方法属于非接触测量,不干扰流场,尤其适用于传统传感器难以应用的高温流场测量。     

(1+2)维各向同性介质中的旋转椭圆空间光孤子

从(1+2)维非局域非线性薛定谔方程出发, 通过坐标变换得到了旋转坐标系下的非局域非线性薛定谔方程. 假设响应函数为高斯型, 用虚时间法数值求解了旋转坐标系下的非局域非线性薛定谔方程的静态孤子解, 迭代出了不同非局域程度条件下的静态椭圆孤子数值解. 最后采用分步傅里叶算法, 以迭代的孤子解作为初始输入波形, 模拟了在不同的非局域程度条件下, (1+2)维椭圆空间光孤子的旋转传输特性. 强非局域时, 椭圆光孤子的长轴方向和短轴方向波形都是高斯型, 其他的非局域程度下, 不是高斯型. 由此表明：(1+2)维椭圆光孤子对非局域程度依赖性很强. 旋转角速度和功率均与非局域程度以及孤子的椭圆度有关.     

Coupling efficiency of single-mode fiber components using GRIN-rod lenses

This article analyzes the characteristics of single-mode fiber (SMF) components using graded-index-rod (GRIN-rod) lenses. The coupling efficiency of the SMF to GRIN-rod lens to SMF coupling system is derived in the general case. The problem is simplified by using the reciprocal field method. All solutions are in closed form. It is found that SMF position tolerance is about 3 μm; the angular tolerance is about 1°. The GRIN-rod lens position tolerance is much less critical while the angular tolerance is extremely small. These tolerances could be much less critical if the fiber is kept near the GRIN-rod lens axis.     

Coupling efficiency of single-mode fiber components using GRIN-rod lenses

This article analyzes the characteristics of single-mode fiber (SMF) components using graded-index-rod (GRIN-rod) lenses. The coupling efficiency of the SMF to GRIN-rod lens to SMF coupling system is derived in the general case. The problem is simplified by using the reciprocal field method. All solutions are in closed form. It is found that SMF position tolerance is about 3 μm; the angular tolerance is about 1°. The GRIN-rod lens position tolerance is much less critical while the angular tolerance is extremely small. These tolerances could be much less critical if the fiber is kept near the GRIN-rod lens axis.