【作者】 何周；

【导师】 李绪友；

【作者基本信息】 哈尔滨工程大学 ， 精密仪器及机械， 2011， 博士

【摘要】 光纤陀螺是光纤传感领域最重要的成就之一,从20世纪末至今的不断研制,在惯性技术领域已经确立了“优先选择”的地位。到目前为止,光纤陀螺主要经历了干涉型(IFOG)、皆振型(RFOG)和布里渊型(BFOG)三代的发展历程。其中,干涉型光纤陀螺技术日趋成熟,并且已经成功应用于各个领域,但温度问题与小型化是其高精度发展的障碍。作为第三代光纤陀螺的BFOG,具有结构简单、信号处理简单、灵敏度和分辨率高、动态范围大、体积小等各种优点,代表了光纤陀螺高精度和小型化的发展方向。随着近几年光纤通信领域相关技术的发展,窄带抽运源、特种光纤、新型高效耦合器等器件的出现给BFOG的发展带来了机遇,因此对这种新型光纤陀螺的研究具有重要的意义。论文的研究内容主要针对BFOG的几个关键问题而展开,论文的主要工作如下：首先对BFOG的工作原理及其灵敏度进行了分析。光纤中的受激布里渊散射效应是BFOG的物理基础,分析了光纤中的布里渊散射理论,推导了布里渊散射阈值功率与光纤的长度及损耗系数的关系,分析了受激布里渊增益谱型与泵浦波的关系,推导了理想状态与实际情况下BFOG的输出拍频公式,对BFOG的潜在精度与理论动态范围进行了研究并给出了定量计算结果,计算结果表明BFOG具有很高的潜在精度与理论动态范围。然后对布里渊光纤环形激光器的输出稳定性进行了研究。布里渊光纤环形激光器是BFOG的核心部分,激光器的输出稳定性直接影响到陀螺的性能。布里渊光纤环形激光器是有源谐振腔,激光器中的谐振特性及光强分析是研究BFOG的基础,对此,推导了光纤环形谐振腔的最佳谐振条件,得出临界耦合态的谐振腔腔内光强最大并且出射光强为零,具有最高的精细度。对布里渊光纤环形激光器中的光强进行了分析,在布里渊光纤环形激光器应用于BFOG中应控制入射泵浦光强在一阶及二阶阈值光强之间。针对影响布里渊光纤环形激光器输出稳定性的偏振和温度两个主要因素进行了深入的研究。理论分析了泵浦光与斯托克斯光偏振态的关系对布里渊增益系数的影响。在激光器腔内泵浦光及布里渊激光两本征偏振态同时谐振,两本征偏振态之间的相位差随温度等环境的波动发生变化从而产生偏振串扰,对此,提出了采用保偏光纤偏振主轴90°旋转熔接及单偏振单模光纤构建光纤环形谐振腔来消除偏振串扰,并进行了实验验证。分析了温度对布里渊频移、阈值光功率、增益系数、激光模式跳变及光路程长的影响,通过计算得出温度对布里渊频移的影响大小约为1.2MHz/℃,影响布里渊阈值光功率温度系数的主要因素是光纤环形腔的参数,布里渊阈值光功率的温度系数约为一961×10-6/℃,温度引起光路程长的变化会给陀螺带入标定因数误差及零偏不稳定。之后研究了BFOG中的主要光学噪声误差,BFOG中存在的主要光学噪声包括瑞利背向散射噪声、磁场Faraday效应及光克尔效应。对泵浦光及布里渊激光的背向散射光对陀螺的影响机理分别进行了研究,计算结果表明背向散射光在光纤环形腔内得到谐振加强,其光强大小约为主光强的百分之一；泵浦光的背向散射光强会增大光纤环形腔的损耗,降低了激光器的精细度,增高了激发布里渊激光的阈值光功率；布里渊激光的背向散射光会与相向传播的激光发生耦合,导致陀螺低转速下拍频输出为零的闭锁现象。从光纤中的Faraday效应入手,分析了BFOG中的Faraday效应误差,建立起了磁场Faraday效应引起的陀螺误差模型,得出陀螺中磁场Faraday效应误差存在的原因是光纤中圆双折射的存在,分析指出了减小Faraday效应误差一方面是增大光纤的双折射△β,即采用高双折射光纤,另一方面是降低光纤的扭转率；对此,理论分析了采用高双折射保偏光纤抑制BFOG中的Faraday效应误差的有效性。建立起了综合考虑光功率差及偏振态因素的光克尔效应误差模型,详细分析了BFOG中产生光克尔效应误差的原因,提出并设计了调制频率为自由光谱范围整数倍占空比为50%的方波信号对泵浦光源进行强度调制消除光克尔效应误差。最后针对BFOG转动时泵浦光的失谐给BFOG带来的影响,开展了BFOG中泵浦光稳频方案的研究。推导了失谐对陀螺动态范围的限制与引起光克尔效应误差大小,针对单光路稳频方案不能完全解决泵浦光失谐对BFOG的影响,提出并设计了双光路稳频方案,对CCW光路泵浦光采用三角波相位调制实现方波频率调制,在CCW光路泵浦光稳频后由陀螺的转速引起的拍频大小即为CW光路泵浦光的失谐频差大小,通过反馈控制实现对CW光路泵浦光的稳频,可以解决泵浦光失谐对BFOG的影响：对BFOG稳频系统进行了整体设计,对光路系统主要光学器件进行了分析及选取,对光纤环形腔腔长选择及缠绕方法进行了设计,设计了稳频与信号检测电路,并对稳频系统进行了测试。更多还原

【Abstract】 The fiber optical gyroscope (FOG) is one of the most important achievements in fiber optic sensor field, through the continuous development of the last years, it has been to establish a "preferred" status in the field of inertial technology. So far, The FOG mainly through three generations which were the interferometer (IFOG), resonant (RFOG) and Brillouin type (BFOG).Among them, the IFOG technology has been matures and successfully applied to various fields, but the temperature and the miniaturization were the obstacle to the development of high accuracy. As the third generation FOG-BFOG, due to the simple structure, simple signal processing, high sensitivity, large dynamic range, small size and other advantages, it was on behalf of the development of high precision and miniaturization. In recent years, with the development of optical communication and related technologies, the appearance of narrowband pump source, specialty optical fiber, new high coupler devices bring a new development opportunity to BFOG, and it is of great significance to study this new FOG. In this research paper, it mainly focuses on several key technologies in the implementation process for BFOG. The main thesis works are as follows:Firstly, the work principle and sensitivity analysis was studied. Optical fiber stimulated Brillouin scattering effect is the physical basis of BFOG, the fiber Brillouin scattering and Brillouin scattering threshold with fiber length and fiber loss were analyzed, the relationship between stimulated Brillouin gain spectrum and pump wave type was studied, the beat frequency formula in theory and considering actual case of BFOG were derived, the potential accuracy and dynamic range of BFOG has been theoretical analyzed and calculated.Then, the output stability of Brillouin fiber ring laser light was studied. The Brillouin fiber ring laser is the core of BFOG and the gyro performance was directly affected by the laser frequency stability. Brillouin fiber ring laser cavity is an active cavity, the stability of laser in resonant cavity was the basis of light intensity analysis. The best conditions for resonance was derived, and it was obtained that the light intensity in resonator cavity was maximum and the emitted light intensity is zero when the resonator cavity is critical coupling state, and then the fineness is the highest. The relationship between the pump light intensity and stokes light intensity was analyzed in Brillouin fiber ring laser, and obtained that the incident pump light intensity should be controlled between the first-order and the second-order threshold intensity. The two major factors were polarization and temperature which affect the output stability of Brillouin fiber ring laser were studied in detail. The relationship between the pump light and stokes light polarization and the Brillouin gain coefficient was theoretical analyzed, the two eigenstates polarization of pump light and Brillouin laser light were resonance in Brillouin resonant cavity at the same time, and the phase difference between the two eigenstates polarization fluctuated due to temperature and other environmental change which resulting in polarization crosstalk. The polarization axis90°rotation and single-polarization single-mode fiber ring resonator to build fiber ring cavity to eliminate the polarization fluctuation were analyzed and verified by experimentally. The temperature on the Brillouin frequency shift, threshold optical power, gain coefficient, the laser mode hopping and optical path length were analyzed and calculated. It can be obtained by calculating that the Brillouin frequency shift by temperature was about1.2MHz/℃, the fiber ring cavity parameters was the mainly factors which affect Brillouin threshold optical power, and the Brillouin threshold optical power temperature coefficient is about-961×10-6/℃, The change of optical path length caused by temperature change will result in scale factor error and gyro bias instability.Thirdly, the mainly optical noise errors in BFOG were studied, the mainly optical noise in BFOG including Rayleigh backscattering, magnetic field Faraday Effect and optical Kerr effect. The backscattering mechanism of pump light and Brillouin laser were studied, the results show that the backscatter light intensity in the fiber ring cavity was resonant enhanced and is about1%of the main light intensity. The backscattering light from pump light will increase the fiber ring loss, and result in the stimulated Brillouin laser threshold increasing. The backscattering light from Brillouin laser light was coupled with the opposite transmitted laser light, and resulting in locking phenomenon. The Faraday Effect in BFOG was analyzed, and the gyro error model was established; and obtained that the error caused by Faraday Effect exists in BFOG was due to the presence of circular birefringence in fiber. There were two ways to reduce the Faraday effect error, one is to use high birefringence fiber, the other is to reduce the twist rate in fiber, the use of polarization maintaining fiber with high birefringence suppress Faraday effect error was theoretical analyzed. The optical Kerr effect error model which considering the light power difference and polarization factors was established, the causes of Kerr effect error in gyroscope was analyzed in detail, then the pump light intensity modulated to eliminate optical Kerr effect was proposed and designed.Finally, the influence of pump light detuning on BFOG was discussed, the pump light frequency stabilization scheme in BFOG was proposed. The expression of the maximum detuning which limited the dynamic range were derived and calculated. Due to the single frequency stabilization can’t solve the influence of pump light detuning on BFOG absolutely, then the dual light path frequency stabilization was proposed and designed. The triangle wave phase modulation was used to achieve square wave frequency modulation in CCW direction of the pump light, and the beat frequency signal of rotation speed is equal to the frequency difference caused by the CW pump laser detuning. The overall system of BFOG was designed, the optical system was analyzed and the main optical devices were analyzed and selected, the signal detection and frequency stabilization circuit were designed, then the system was tested.更多还原