Study Of Suppression For Light Source Intensity Noise In High-precision FOG

Super-fluorescence erbium-doped fiber light source with good wavelength stability, wide optical spectral type and high optical power to become the first choice for high-precision fiber optic gyroscope. High output power can improve the signal to noise ratio and decrease angle random walk of FOGs, but the light intensity increases to a certain extent, the signal to noise ratio of FOGs will be decided by erbium-doped fiber source intensity noise,not to increase further with the optical power to increase. To further improve the precision of FOG,the light source intensity noise must be suppressed. First, the subject of theoretical analysis of erbium-doped fiber light source intensity noise generation mechanism, and then were used to the external light intensity modulation method and the digital subtraction method light source intensity noise suppression, in order to achieve the purpose of improving high-precision fiber optic gyroscope. The subject of the work done mainly in the following areas:First of all, the atomic spontaneous emission, stimulated emission and stimulated absorption were analyzed in the light-emitting mechanism, the atomic transition of the three-level system and the four-level system models were established. Then the three-level erbium-doped fiber and erbium-doped fiber source system's basic components wre analyzed in detail, the various factors of the light source intensity noise wre analyzed.Secondly, the principles and indicators of performance parameters on the integrated optical intensity modulator was analyzed. And then a feedback control circuit was designed, and the structural parameters to determine the method were studied detailedly. Finally, a feedback control circuit model was established, by simulation methods, the light source intensity noise at the bias modulation frequency and the odd harmonics of the bias modulation can be suppressed better.Next, the feasibility of digital circuit subtraction was analyzed theoretically, and then verify the correlations between gyro noise signal light and reference light source by the experimental means, obtained that Y waveguide polarizer destroyed two related optical signal. Then propose put a pigtail in the light polarizer means to resolve the two polarization states of light signals the issue of consistency. Finally the specific method on the subtraction circuit was advanced, and gives the method to determine two key parameters about delay time and gain coefficient.Finally, by analyzing that the light source intensity noise impact on random walk coefficient of optical fiber gyro, Allan variance analysis was lead to gyro output noise. The advantages and disadvantages on the light intensity external modulation method and the digital circuits subtraction was compared detailedly, and points out the technical problems need to improve, as the light source intensity noise suppression technology to further enhance a positive role.