Study On Space Environmental Adaptability Of Erbium-Doped Photonic Crystal Fiber Source

With the development of space science and technology, the application about radiation resistant fiber source for high precision fiber optic gyroscope is required urgently. As an excellent candidate for interferometric fiber optic gyroscope, erbium-doped superfluorescent fiber source has a broad application prospect. However, the space radiation environment will lead to obvious decay of the output characteristics of the fiber source, which is mainly reflected in the mean wavelength drift and the radiation-induced attenuation of output power, and they directly affect the precision and sensitivity of fiber optic gyroscopes.The problem of the adaptability of the fiber source for high precision fiber optic gyroscope in the space radiation environment has been mainly concerning. In this thesis, a radiation resistant and high stability erbium-doped photonic crystal fiber source was studied and developed. The major contents and results can be listed as follows.(1) The radiation characteristics of erbium-doped photonic crystal fiber source was experimentally studied. Three sets of double-pass backward configuration fiber sources, based on three segments of erbium-doped photonic crystal fiber with different lengths, were designed and, performed 500 Gy of dose gamma irradiation experiment and 800 hours of annealing test. Results show that the radiation induced attenuation of 1530 nm band signal light is less than that of 1560 nm band, and that the radiation induced attenuation of 1560 nm band signal light is responsible for the short-band drift of the mean wavelength.(2) The mean wavelength stability technique of the fiber source under irradiation environment was studied. For the study of the short-band drift of the mean wavelength, doublepass forward and double-pass backward configuration fiber sources were filtered and shaped with Gauss-like spectral filtering and shaping technique, and tested under dose rate of 2.988 Gy/h and 7.2 Gy/h irradiation environment. Results show that, after the spectral shaping and filtering, the stability of the mean wavelength improves by approximate 25 times and that, mean wavelength drift is less than 40 ppm under 500 Gy dose of radiation, which confirms that the method for improving the mean wavelength stability of the fiber sources under irradiation environment is of significant effect.(3) The output power stability technique of the fiber source under irradiation environment was studied. The drive current of the pump LD is adjusted by feedback control so as to compensate the radiation induced attenuation of the fiber source power. Through the optimization of the hardware control circuit and PID algorithm, excellent stability of the fiber source was obtained. Results show that the output power changes of the fiber source are 0.253% and 0.349% at room temperature and high-low temperature environmental(-40 ℃~70 ℃), respectively. In addition, under dose of 500 Gy of irradiation, the output power change and mean wavelength drift of the fiber source are less than 1.5% and 40 ppm, respectively. Furthermore, under irradiation dose larger than 1000 Gy, the output power change and mean wavelength drift of the fiber source are only 2.31% and 47.637 ppm, respectively.In this thesis, the space environment adaptability of the erbium-doped photonic crystal fiber source is dramatically improved by the combination of the Gauss-like spectral shaping and filtering method and digital close-loop optical power feedback control technique. The research results are of great significance in promoting the development and application of high precision fiber optic gyroscope in space environment.