Research On Erbium Doped Fiber Source For High Accurate FOG

The fiber optical gyroscope (FOG) is recognized as the summit of the optical fiber sensors, which is researched by many graduate schools both in country and outside. The FOG is a complex system. The method of the FOG to measure rotation is to measure the intensity of light on which the rotation is loaded. So the performance of the source in the FOG decides the performance of the FOG directly.The paper studies the basic principle of FOG at first. The influence of the source bandwidth, source power and source spectrum on FOG is analyzed based on the FOG postulate. A conclusion that is educed from the analysis is that the source suit for FOG should have wide spectrum, high power and high stability. Several wide spectrum sources are studied and the preferred source for FOG is the superfluorescent fiber source (SFS). To be continued, the postulate of SFS is introduced and the erbium-doped fiber source (EDFS) which is a type of SFS is chosen as our object. Then the theory model of the EDFS is introduced based on the three-level system.After the study on the theory, the pump and the configuration of EDFS are designed respectively based on previous studies. A digital control system is designed for the pump source, which contains the power detected circuit, temperature detected circuit, constant current circuit and thermo-electric cooler driven circuit. The control algorithms of power and temperature are realized in FPGA. During the design of the construction of EDFS, five basic structures of EDFS are introduce and compared at first. The double pass backward structure is adopted. Then the principle of isolator is introduced and the isolator is adopted to eliminate the influence of feedback effectively. Besides, the influence of pump polarization and solutions are introduced. At last, gain flattened filters used for EDFS are introduced and flattening the source is realized.At the end of the paper, we test the source system. The performance of pump source is tested at first. The variety of pump temperature is below 0.1℃. The stability of pump power and the precision of control overmatch 0.1%. These data explains that the performance of pump source accord with our goal. Then the stability of EDFS mean wavelength is tested and the influence of pump power, pump wavelength and fiber length on stability of source mean wavelength is analyzed. Through optimize structure parameters of the source, the stability of the source mean wavelength achieved 10ppm, which suit for FOG.