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

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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.