Stabilization of Fiber Optic Brillouin Ring Laser and its Application to Active Fiber Optic Gyros

本研究的主要目的是建立第三代光纤陀螺仪不可缺少的光纤布里渊环激光器的稳定激光器；有源型光纤陀螺。此外，还研究了包括稳定光纤布里渊环激光器在内的陀螺系统的性能恶化因素和输出信号处理方案。在两年的研究期间，首先研究了光纤谐振腔中布里渊散射产生激光的过程，详细考虑了光纤谐振腔中光的偏振特性。分析了在拼接处偏振轴旋转90度的保偏光纤环谐振腔的特性，表明这种结构能有效地稳定激光。本文还阐明了由单偏振单模光纤组成的谐振腔具有稳定的激光特性。建立了前一种结构的实验装置，成功地证明了理论所描述的特性。激光特性还受增益介质沿长长度即约10m的光纤的增益谱分布的影响。我们成功地分析了它们的作用，以阐明温度和/或沿光纤的张力分布对激光特性的影响。此外，还研究了一种消除使灵敏度急剧下降的摇入现象的方法，以及一种从陀螺输出中找到旋转方向的方法。提出并研究了由掺铒光纤组成的稳定环形激光器结构和由光折变光纤光栅组成的稳定无源环形谐振腔。通过这些研究，获得了实现光纤布里渊环激光陀螺的基础和重要知识，这也是本研究的目的。

The main purpose of this research is to establish the ways to stabilize the lasing of a fiber optic Brillouin ring laser, which is an indispensable element of the third generation fiber optic gyroscope ; the active type fiber optic gyro. Moreover, performance deterioration factors and output-signal processing schemes are studied on the gyro system including the stabilized fiber optic Brillouin ring laser.During the two year research period, at first, the process to generate the laser light through the Brillouin scattering in the fiber resonator has been investigated, considering the polarization property of the lights in the resonator in detail. Analyzes of the characteristics of a polarization-maintaining fiber-ring-resonator with 90 degree polarization axis rotation at the splice have shown that this configuration is effective to stabilize the lasing. It has been also clarified that the resonator composed of a single-polarization single-mode fiber shows the stable lasing. The experimental setup of the former configuration has been constructed, which has successfully demonstrated the characteristics depicted in the theory. The lasing characteristics is also influenced by the gain spectrum distribution along the long length of the gain medium, that is, the fiber of about 10m. We have successfully analyzed their effect to clarify the influence of the temperature and/or the tension distribution along the fiber on the lasing characteristics. Moreover, a away to remove the rocking-in phenomena, by which the sensitivity drastically decreases, and a way to find the direction of the rotation from the gyro output have been studied. A stable ring laser configuration made of Er doped fiber and a stable passive ring resonator made of photo-refractive fiber grating have been also proposed and studied.Through these studies, the basic and important knowledge to realize the fiber optic Brillouin ring laser gyro have been obtained, which are the purpose of this study.