用后向散射压缩器产生超高强度激光

报道自制的一台小型的激光系统,用后向布里渊散射与光栅压缩系统组合,把5ns激光脉冲压缩到40ps,压缩率大于100倍.     

高散射抑制比激光雷达水下探测技术探析

浅海海水严重的后向散射是阻碍激光近海水下探测应用的关键问题,回波信号中的后向散射制约了水下目标探测深度、分辨率和对比度.针对该问题,研究了两种高散射抑制比海洋激光雷达——混沌脉冲激光雷达和相干双频脉冲激光雷达,这两种激光雷达信号具有内在的高频强度调制特性,而后向散射具有低频特性.因此,在目标信号光和后向散射光同量级条件下,可通过带通或高通滤波将海水后向散射滤除,从而提高系统信噪比.     

激光在水中气泡微粒的后向散射特性

从激光能量、目标位置、视场大小及气泡厚度等方面对气泡后向散射特性进行研究.采用实验方法研究脉冲激光气泡后向散射特性.实验结果表明,增大激光能量在一定程度上可以有效地改善气泡探测的效果,而气泡发生器位置和视场的合理选择使得气泡探测更容易些,气泡区域厚度的变化对气泡后向散射并没有明显的影响.该实验结论与蒙特卡洛数值模拟的结果一致.     

基于Fournier Forand体积散射函数的水中激光脉冲后向散射特性分析模型

基于Fournier Forand体积散射函数,建立了一种水中激光脉冲后向散射仿真模型.运用该模型可用Monte Carlo方法模拟光子在水中的传播过程,并得到光波后向散射的冲击响应.将初始激光脉冲与冲击响应进行卷积并求其傅里叶谱,即可得到激光脉冲后向散射信号的时域和频域特征.利用该模型分析了入射为高斯型激光脉冲时,水中散射体的尺度分布、散射体与纯水的相对折射率以及水体衰减系数对激光脉冲后向散射特性的影响.结果表明：随着小尺度散射体相对数量的增多、散射体与纯水相对折射率的增加、水体衰减系数的增大,激光脉冲后向散射信号能量增强,宽度增加,低频分量显著增大.     

基于Fournier Forand体积散射函数的水中激光脉冲后向散射特性分析模型

基于FournierForand体积散射函数,建立了一种水中激光脉冲后向散射仿真模型.运用该模型可用MonteCarlo方法模拟光子在水中的传播过程,并得到光波后向散射的冲击响应.将初始激光脉冲与冲击响应进行卷积并求其傅里叶谱,即可得到激光脉冲后向散射信号的时域和频域特征.利用该模型分析了入射为高斯型激光脉冲时,水中散射体的尺度分布、散射体与纯水的相对折射率以及水体衰减系数对激光脉冲后向散射特性的影响.结果表明：随着小尺度散射体相对数量的增多、散射体与纯水相对折射率的增加、水体衰减系数的增大,激光脉冲后向散射信号能量增强,宽度增加,低频分量显著增大.     

脉冲宽度对云雾回波的影响研究

云雾后向散射会产生引发激光引信虚警的回波信号.基于蒙特卡罗法,对云雾散射回波进行了模拟仿真,并定量给出了云雾散射回波的波形、波峰位置、脉宽和峰值功率随发射脉冲宽度的变化规律.研究结果表明,回波峰值功率随着发射脉宽的增大而增大,且当发射脉宽增大到50ns后趋于饱和,峰值功率将不随脉冲宽度的变化而变化;脉冲展宽的程度随发射脉宽的增大而减弱;发射脉宽对云雾散射回波波峰位置的影响较小.给出的回波信号模拟仿真结果可以为窄脉冲激光引信的目标识别以及探测阈值和脉冲宽度等参量的优化设计提供依据.     

脉冲宽度对云雾回波的影响研究

云雾后向散射会产生引发激光引信虚警的回波信号.基于蒙特卡罗法,对云雾散射回波进行了模拟仿真,并定量给出了云雾散射回波的波形、波峰位置、脉宽和峰值功率随发射脉冲宽度的变化规律.研究结果表明,回波峰值功率随着发射脉宽的增大而增大,且当发射脉宽增大到50ns后趋于饱和,峰值功率将不随脉冲宽度的变化而变化;脉冲展宽的程度随发射脉宽的增大而减弱;发射脉宽对云雾散射回波波峰位置的影响较小.给出的回波信号模拟仿真结果可以为窄脉冲激光引信的目标识别以及探测阈值和脉冲宽度等参量的优化设计提供依据.     

旋转调制捷联惯导激光陀螺仪误差自补偿新方法

基于旋转调制的自补偿技术是进一步提高激光陀螺仪捷联惯导系统导航精度的有效方法.研究了旋转调制捷联惯导系统中的激光陀螺仪误差补偿方法.建立旋转式捷联惯导系统激光陀螺仪的误差传播方程,分析激光陀螺仪旋转误差效应及误差传播特性,在此基础上建立了调制策略编排目标函数;研究了双轴交替旋转调制模式下的调制策略编排方案,提出了一种改进的16次序双轴交替旋转调制方法,建立了基于双轴转动角速度的动态误差方程,实现了转动过程中激光陀螺仪的常值项误差、标度因数误差、安装误差的有效补偿,进一步抑制速度误差积累所引起的位置误差.仿真结果验证了该方法的有效性,提高了捷联惯导系统导航精度,可为旋转调制光学捷联惯导系统设计提供理论参考.     

激光脉冲宽度对远距离尾流气泡后向检测的影响

为了分析激光脉冲宽度对远距离尾流气泡后向检测的影响,基于FournierForand体积散射函数,通过MonteCarlo方法建立了水中激光脉冲后向散射信号时域特征的分析模型.利用该模型研究了初始激光脉冲宽度不同时,水中远距离舰船尾流气泡的激光脉冲后向散射信号变化情况.结果表明:随着初始激光脉冲宽度的增加,后向散射信号中水体散射信号与尾流气泡回波信号的轮廓变得模糊|当脉冲宽度增大到一定程度时,无法从后向散射信号中辨别出回波信号|并且,随着尾流区气泡散射强度的减小以及气泡区与检测器之间距离的减短,这种变化趋势变得更加明显.基于仿真结果,提出一种基于逆卷积运算的尾流气泡回波信号提取方法.     

激光脉冲宽度对远距离尾流气泡后向检测的影响

为了分析激光脉冲宽度对远距离尾流气泡后向检测的影响,基于Fournier Forand体积散射函数,通过Monte Carlo方法建立了水中激光脉冲后向散射信号时域特征的分析模型.利用该模型研究了初始激光脉冲宽度不同时,水中远距离舰船尾流气泡的激光脉冲后向散射信号变化情况.结果表明:随着初始激光脉冲宽度的增加,后向散射信号中水体散射信号与尾流气泡回波信号的轮廓变得模糊|当脉冲宽度增大到一定程度时,无法从后向散射信号中辨别出回波信号|并且,随着尾流区气泡散射强度的减小以及气泡区与检测器之间距离的减短,这种变化趋势变得更加明显.基于仿真结果,提出一种基于逆卷积运算的尾流气泡回波信号提取方法.     

空间正交三轴激光陀螺的调腔技术

通过分析传统激光陀螺的调腔方式,提出了激光陀螺应在实际工作条件(具有增益能力状态)下进行调腔的观点,以及通过控制其腔长或光程长来控制反射镜的反射方向的调腔方法,并相应地设计了新的腔长控制镜结构。通过全面扫描的方式,找出了空间正交三轴激光陀螺的三腔在高质量运转时的最佳角度控制参数,解决了空间三轴激光陀螺高精度调腔的难题。     

Direct dither control without external feedback for ring laser gyro

To avoid the lock-in effect, a body dither is introduced for the ring laser gyro (RLG). A dither feedback signal is necessary to control the dither drive signal. In the current dither control method, a piezoelectric or electromagnetic transducer is often used to obtain the dither feedback. The read-out signal of the RLG contains all dither-related information; hence, dither feedback can be obtained from the read-out signal, and external feedback can be reduced. A novel dither controlling method without external feedback is introduced in the present paper. How to control the dither amplitude and track the resonant frequency of the dither motor is described in detail. A comparative experiment is conducted between the old dither control method and the new one. Results show that the output of RLG using the new method has the same accuracy as that using the old method, aside from having more compact circuit dimensions.     

Model of lock-in in a ring laser and a semiconductor laser gyro

It is assumed that the process of lock-in in a ring laser has a finite transient time. This assumption serves as a basis for developing a semiconductor laser gyro. A semiconductor optical amplifier is applied as an amplifying medium, and a ring resonator represents a long optical fiber. The injection of an external single-frequency light into a ring resonator with subsequent circulation of counterpropagating waves is used. The light characteristics of the semiconductor laser gyro are discussed, and the rotation sensitivity of the gyro is demonstrated.     

机械抖动激光陀螺的高分辨率信号处理

 机械抖动激光陀螺（MDRLG）信号是两路相位差为π/2的正弦拍频信号,一般采用4倍频鉴相输出计数脉冲,利用FIR滤波和抖动剥除等方法解调抖动信号,从而得到外界输入的角速度信息。高速采集MDRLG信号,并细分为相位依次相差π/16的16路信号,实现MDRLG的8倍频、16倍频和32倍频鉴相输出。输出角速率的均方差随着倍频数的提高而减小,信号处理的分辨率得到提高。实验测试和Allan方差分析表明：32倍频时的量化误差Q从4倍频鉴相时的0.327″减小到0.170″,增加MDRLG信号鉴相的倍频数可以减小量化误差。在对MDRLG信号进行抖动剥除解调时,由于量化误差是主要误差源之一,高分辨率信号处理能够有效提高MDRLG角速度测量的精度。     

Analysis of nonlinear response in a body dithered ring laser gyro

We present a solution of the dither equation in a ring laser gyro. This solution is based on an application of Floquet theory to the linear equation derived from the original dither equation. The circumvention of the zero locking band as well as the appearance of higher order locking zones are discussed.     

机械抖动激光陀螺新型信号处理方法的研究

针对高速采样低通滤波的线性脉冲响应(FIR)滤波器在机械抖动激光陀螺(MDRLG)信号处理中存在着较大的时延,限制MDRLG在快速跟踪中的应用,基于相关滤波技术提出了一种新的信号处理方法。对这一方法的基本理论进行了分析,并基于Labview实现了仿真。相关滤波后,激光陀螺输出中的抖动信号衰减了约41dB,还不能达到激光陀螺应用的要求,可以适当加一低阶的FIR低通滤波器去除抖动剥除后剩余的抖动成分和高频噪声。在静态条件下用这三种信号处理方法分别对激光陀螺零偏进行了测试。相关滤波法所测得零偏稳定性(1σ00)比50阶FIR滤波器差了将近三倍,相关滤波后再经过22阶的FIR低通滤波测得的零偏稳定性比50阶FIR低通滤波器的测试结果大了不足0.001°/h,延迟时间却从4.9ms减小至2.1ms。     

Effect of backscattering on the behavior of a dye ring laser

The effect of backscattering on the behavior of a dye ring laser is investigated by photoelectric counting measurements. It is found that there exist two laser regimes, a low backscattering regime in which the laser exhibits meta-bistability and random mode switching, and a high backscattering regime in which switching is suppressed. In the latter case the photon statistics are similar to those of a single-mode standing wave dye laser.     

Full investigation of the backscattering in resonator fiber optic gyro

Resonator Fiber optic gyro (RFOG) is a high accuracy inertial rotation sensor based on the Sagnac effect. The optical fiber ring resonator (OFRR) is the key rotation sensing element. The backscattering characteristics of the OFRR are fully investigated. The Rayleigh backscattering dominates the backscattering spectrum with the input power below the threshold. High carrier suppression is crucial to reduce this Rayleigh backscattering error. Being different from the intrinsic Rayleigh scattering of the fiber, the stimulated Brillouin scattering (SBS) in the OFRR should be avoided. This is because the finesse and the resonance notch depth of the OFRR decrease for the pump depletion through the SBS process. The shot noise limited sensitivity (SLS) of the RFOG is improved by increasing the input power. Through analysis, it is found that the threshold input power is improved after phase modulation. The SLS of the RFOG is analyzed at different modulation parameters and its relevant SBS threshold. Accordingly, the optimized modulation frequency and the corresponding maximum input power are all obtained. A simple method of testing the frequency shift in the SBS is also proposed. In this method, the central frequency of the laser source is locked to the resonance frequency of the OFRR in one direction. A steady SBS light is observed and its frequency shift is measured together.     

Feature analysis of the scale factor variation on a constant rate biased ring laser gyro

Scale factor of a constant rate biased ring laser gyro (RLG) is studied both theoretically and experimentally.By analyzing experimental data, we find that there are three main terms contributing to the scale factor deviation. One of them is independent of time, the second varies linearly with time and the third varies exponentially with time. Theoretical analyses show that the first term is caused by experimental setup,the second and the third are caused by un-uniform thermal expension and cavity loss variation of the RLG.