Research On Four-mode Differential Brillouin Fiber-Optic Gyroscope And Its' Laser's Frequency Stable Technology

Brillouin fiber-optic gyroscope (B-FOG) is an active type of fiber-optic gyroscope based on a nonlinear optics effect-the stimulated Brillouin scattering (SBS). It is attractive because it has advantages of both ring laser gyroscope and fiber-optic gyroscope with compact configuration, direct frequency readout for the rotation rate and wide dynamic range. Therefore, it gives the development trend of high precision, compact fiber-optic gyroscope.Firstly, based on investigation of Brillouin fiber-optic scheme both domestic and abroad, a novel four-mode differential Brillouin fiber-optic gyroscope is projected which can discern rotation direction and reduce lock-in phenomenon. Operational machnic of the Brillouin fiber-optic scheme are analyzed.Secondly, theoretical and experimental results are given to the Brillouin fiber ring laser which is the foundation of B-FOG. In theory, circulating and transmitted intensities in ring cavity or Brillouin fiber ring laser are analyzed in detail especially in the first window and the second window. The resonance characteristics are also analyzed. In experiment, the key component of the B-FOG, fiber-optic ring cavity is designed, which gives the resonance curve by changing the frequency of pump laser. The experimental results of the cavity and the characteristics of Brillouin fiber ring laser are also given. The finesse of the resonator is 70 and the threshold of the Brillouin ring laser is 1.321mW.At last, the frequency stable technology of the Brillouin fiber ring laser is studied. The hardware and software of the frequency stable circuit are designed using the digital DC frequency stabilization principle. The test results are also given in the paper. This gives the developing base of four mode differential Brillouin fiber-optic gyroscope.