Studies On Optical Noises And Signal Detection Technology In Resonator Fiber Optic Gyro

Fiber optic gyro is a high accuracy inertial rotation sensor based on the Sagnac effect. It plays an important role in the field of navigation and guidance.Compared with the interferometer fiber optic gyro (I-FOG), the resonator fiber optic gyro (R-FOG) shows advantages in high accuracy and the miniaturization.This dissertation includes further analysis on signal detection and optical noises suppression technique. The main innovational work and achievements can be concluded as follows:1. A digitalized method of phase modulation spectroscopy technique is proposed based on the CORDIC algorithm. The generation of modulation signal, synchronous demodulation and signal processing in R-FOG can be realized in a single FPGA. The accuracy of the detection system is about 28 nV which can satisfy the demand of 10-3°/s. The time of frequency locking is about 40 ms based on a digital PI controller. The bias stability of demodulation signal in the frequency servo loop is 15μV(1σ)whose equivalent fluctuation of frequency deviation is 0.12 Hz.2.The characteristics of Rayleigh and stimulated Brillouin scattering (SBS) are analyzed.It is helpful to increase the limit rotation sensitivity (LRS) by increasing the input power of the fiber ring resonator (FRR). However the R-FOG can not work when the SBS occurs.So the input power of FRR is limited by the SBS threshold power. Analysis shows that the SBS threshold power increases along with the modulation frequency. So it is meaningful to increase the SBS threshold power by increasing the modulation frquency, and then to increase the LRS of R-FOG. However the slope of demodulation will decrease while the modulation frequency is higher and it will decrease the LRS.Through the analysis, the best modulation frequency considering SBS can be got which has the best LRS of R-FOG.3.A polarization model of FRR is established based on the transfer function. An additional Kerr effect error-caused by the polarization fluctuation is found and investigated. Under the typical parameters, the additional Kerr effects are 4×10-3°s and 2.89×10-2°s in a FRR with two and single 90°splices, respectively. The polarization noise caused by the polarization dependent loss (PDL) of the fiber coupler is large in a reflection mode of FRR, while it is small in a transmission mode of FRR. In experimental we test and compare the bias stability of R-FOG with reflection and transmission mode of FRR which are 0.14°/s and 0.018°/s. The experimental results are coherent with the theory analysis. The research above show that a transmission mode of FRR with two 90°splices has the better stability of temperaure and has the less additional optical Kerr effect error.Based on the above work, an all digitalized R-FOG experimental system using fiber laser is set up. In this R-FOG, a transmission mode of FRR is adopted whose length and diameter are 16 m and 0.12 m, respectively. The bias stability of the R-FOG is about 28°/h(1σ)for 1 hr and 10 s integration time. To our knowledge, this result is the best long time bias stability of R-FOG using a miniatured fiber laser.