Design of light source for ultra-high precision fiber optic gyroscope

Abstract

Firstly, the requirements of ultra-high precision gyroscope for light source are analyzed. Ultra-high precision fiber optic gyroscope (FOG) is used in long-term inertial navigation system for naval vessels, which requires high precision, stability of scale factor and nonlinearity of scale factor. The stability of the average wavelength of the light source directly affects the stability of the scale factor of the FOG. The high power output of the light source combined with other noise reduction methods can improve the signal-to-noise ratio of the FOG, thereby improving the detection accuracy. The coherence of light source spectrum will affect the coherent noise of the FOG, the symmetry of spectrum will affect the nonlinearity of scale factor, and the spectral width will affect the noise level. Therefore, ultra-high precision FOG requires high power, high wavelength stability, large spectral width, hyperspectral symmetry and low coherence light source. Second, an ASE source for ultra-high precision FOG is proposed in this paper. In terms of optical path, the optical path structure of ASE light source and the means to improve the average wavelength stability of the light source are analyzed. Two-stage Erbium fiber structure is used to obtain high power output. Faraday rotating mirror is used to reduce the polarization-dependent gain in Erbium fibers. High stability of average wavelength is achieved by optimizing erbium fiber parameters and pump power. The non-subpeak Gauss spectrum of the coherence function is chosen as the spectral scheme. In the design of the filter, the orthogonal experiment and hardware-in-the-loop simulation are used to optimize the filter parameters and perform the whole spectrum shaping filtering. The output spectrum width is over 20 nm, which is much wider than 7-13 nm of traditional filtering method，and reduces the noise of gyro noise. In the drive circuit, the high stability temperature control of the pump is realized. By controlling the temperature characteristics of the feedback loop devices, the power stability of the light source is greatly improved by using the power feedback mode. The ASE light source designed above can provide power output of more than 30 mW. The wavelength stability is less than 5 ppm in the whole temperature range, and less than 1 ppm at the constant temperature. The power variation is less than 1%, and the spectrum width of output is more than 20 nm. It is an ideal light source for ultra-high precision fiber optic gyroscope..