Study On The Ring Resonator And Lock-in Phenomenon Of Brillouin Fiber Optic Gyroscope

As the third generation fiber-optic gyroscope, Brillouin fiber-optic gyroscope (B-FOG) is on behalf of the development direction of fiber optic gyroscope with high precision and miniaturization. Because it has the advantages of small size and frequency direct read out, so it is more applicable to the strap-down inertial navigation system, but in the international there is only research in theoretical stage. This article first researches the basic issues in B-FOG, such as the B-FOG working principle is analyzed, the B-FOG fiber ring resonator is researched and designed, the study on B-FOG threshold power and the cause of the lock-in phenomenon ,then the suppression methods of lock-in phenomenon are proposed. In detail studies as follows:Firstly, the B-FOG working principle is analyzed in depth. Based on the analysis of Sagnac effect, Stimulated Brillouin scattering effect in the optical fibers is detailed analyzed, and the beat frequency mechanism of Brillouin fiber-optic gyro is investigated.Secondly, the optical power threshold and polarization stability in B-FOG are analyzed.Theoretically studied at the stability of pumped light and stimulated Brillouin light when polarization spindle rotating at a different angle, and the formulas between threshold with fiber optical length and radius of step refractive index and square refractive index polarization maintaining fiber is presented, and the Brillouin fiber-optic gyroscope resonator threshold is tested by experiment.Thirdly, the Brillouin fiber-optic gyroscope resonator is researched and tested, the Brillouin cavity is the core of Brillouin fiber-optic gyros, the basic structure and principles are investigated initially, then the light intensity in the resonant cavity are analyzed, then the Brillouin fiber-optic resonant cavity is designed, the theoretical results are verify by experimental tests.Finally, the lock-in phenomenon in B-FOG is researched and analyzed in detail, first the causes of lock-in phenomenon is researched, then the beat frequency formula which consider the existence of lock-in phenomenon and input-output expression are established, and the partial frequency method and push-pull phase modulation were studied in detail, finally, the principles and advantages of the four-frequency differential system scheme is analyzed in detail.