With the development of micro and small aircraft, unmanned systems, autonomous driving, wearable human navigation technology, missile guidance, and other fields. Accuracy is no longer the only core indicator of inertial navigation systems. Low cost, size, quality, and power (CSWaP) have become the key to enhancing the competitiveness of inertial technology products. Due to the large size and independent packaging of optical components, it is difficult to improve the CSWaP comprehensive performance of fiber optic gyroscopes (FOGs) under traditional solutions. Currently, using integrated optical technology to realize the integration of FOGs is the main way to reduce the comprehensive indicators of CSWaP of FOGs. Integrated FOGs refer to FOGs that use integrated optical chips to partially or completely replace optical devices of traditional FOGs. In this article, we propose a design scheme for a specialized integrated device of three-axis FOGs, which can achieve the integration of the main optical components of the interferometric fiber optic gyroscope optical path. It is of great significance for promoting the development process of miniaturization, lightweight, integration, low power consumption, and low cost of FOGs.
We propose an electric-arc based scheme to generate the intensity-controllable weak polarization mode coupling (PMC) points in polarization maintaining fiber (PMF). The PMC intensity can be readily controlled from -70dB up to -40dB. The insert loss introduced by the scheme is negligible since it does not need to break and splice the PMF.As an example, we demonstrated a piece PMF with three introduced PMC points as a quasi-distributed temperature sensor at last.
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..
With the increasing demand of navigation and positioning services, the accuracy and safety of traditional navigation system have been limiting factor of future application. The development of quantum technology brings hope to the research and development of a new generation of navigation system. In this paper, the application of quantum technologies in fiber optic gyroscope is introduced and analyzed.
As a high-precision angular rate sensor, high-precision fiber optic gyroscope (HP-FOG) can be used for space positioning, strategic missile guidance and submarine navigation. With the further improvement of the demand for navigation accuracy under deep and open sea conditions and satellite rejection conditions, the goal is to manufacture FOG with higher accuracy and sensitivity. The noise of FOG has become the key to restrict its application in high-precision field. In this paper, the noise source of FOG is analyzed, and the method of using semiconductor optical amplifier to suppress relative intensity noise and feedback adjustment to reduce noise is given. In theory, we propose a scheme of FOG using three photon states as light source to improve the detection sensitivity. In theory, this scheme can realize three times super-resolution measurement.
The temperature drift causes the zero-bias drift of the fiber optic gyroscope to show complex nonlinear changes, which seriously restricts the measurement accuracy of the fiber optic gyroscope. Therefore, it is necessary to establish an accurate temperature compensation model to compensate for the temperature drift of the fiber optic gyroscope.In order to effectively improve the output accuracy of the fiber optic gyroscope under the condition of the full temperature range, the static full temperature bias test of the fiber optic gyroscope is first designed to obtain the bias data of the fiber optic gyroscope under the temperature change condition of -40℃~60℃. Secondly, on the one hand, a polynomial regression model is gradually established with temperature, temperature change and multiple powers as independent variables. On the other hand, the RBF neural network model is established after screening the input variables with the MIV algorithm. Finally, two models are used to achieve zero-bias temperature compensation. According to the compensation results, both can effectively improve the full temperature output accuracy of the fiber optic gyroscope. Compared with the polynomial regression model, the RBF neural network model can identify temperature drift more effectively and accurately, and greatly improve the output accuracy of the fiber optic gyroscope in the full temperature range.
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