Compared with laser gyro, the scale factor performance of high-precision FOG(HPFOG) restricts its application to high-precision and strategic applications. According to the characteristics of HPFOG with well temperature sensitivity and poor nonlinearity, In this paper, the temperature error model of fiber optic loop and the scale factor error output curve of gyro at different angular rates of each temperature point are analyzed. An optical fiber temperature sensor embedded in the optical fiber loop is proposed to accurately measure the temperature of the optical fiber loop. Compared with the existing single point or multi-point external temperature model, the model can accurately measure the internal temperature field of the optical fiber loop, and establish a reliable Shupe error model of the optical fiber loop temperature. A hybrid model is established by introducing the input angular rate information of gyroscope into the model, and the multi coefficient scale error is compensated according to the model. The experimental results show that the scale factor of HPFOG is greatly improved after compensation based on the accurate error model, and the performance index of the scale factor of HPFOG is effectively improved.
As a kind of all solid-state FOG, high-precision FOG(HPFOG) has the characteristics of anti-shock and anti-vibration. However, when it suffers strong shock, the gyro structure and fiber loop will produce high-frequency resonance components. The projection of the resonance component in the sensitive axis of the gyro is equivalent to the input of high frequency angular vibration of the gyro, and when the frequency approaches or exceeds the working frequency of the gyro, the gyro feedback loop will generate positive feedback. Due to the low frequency of the feedback loop of HPFOG, the above-mentioned positive feedback results that the output of the cross-stripe, which makes the gyro output the wrong angular rate information. In this paper, the closed-loop feedback loop model and the structural mode of FOG are modeled and analyzed, and the mechanism of cross-stripe is discussed in detail. Then, three methods of restraining cross-stripe are given by combining the closed-loop algorithm, and the advantages and disadvantages of the method are analyzed. Finally, the test results show that the three methods can effectively suppress the HPFOG cross-stripe, and improve the HPFOG's ability to resist strong impact.
The random walk coefficient of fiber optic gyroscope (FOG) is a kind of gyroscope output error accumulated over time by white noise. In order to achieve 100s bias stability of high precision FOG less than 0.0001 °/h, the random walk coefficient of FOG is less than 0.0000167 °/√ht. Based on the analysis of the factors affecting the random walk coefficient of FOG, a random walk coefficient model is established in this paper. Considering the characteristics of high precision FOG such as oversampling and low bandwidth, a method to reduce the random walk coefficient of high precision FOG is proposed. Through the theoretical analysis of the above methods, the feasibility of the method is proved theoretically. Furthermore, the comparative test of the precision of the high precision fiber optic gyroscope using the above method proves the feasibility of the above method. The random walk coefficient of the gyroscope is significantly reduced, which makes the bias stability of the high precision fiber optic gyroscope achieve the design goal.
On the base of an analyzing system, we demonstrate a testing method to reveal whether the FOG scale factor is stability after a long term ageing. The temperature of the chamber is set to 85°C in order to accelerate ageing of the adhesive. The FOG scale factor data is sampled each month. Results show that the MTTF (Mean Time to Failure) of the FOG coils is not satisfied with the application need. The analyzing system has good application prospects in testing the instabilities of the FOG’s Scale Factor.
With the rapid development of FOG inertial navigation technology in China, it is possible for FOG inertial navigation system to achieve " one nautical mile in a month" navigation accuracy under temperature control environment. As the core component of FOG inertial navigation system, the performance of high precision FOG directly affects the accuracy of navigation system. Even in a good temperature control environment, the current performance index of high precision FOG is not enough to support the navigation accuracy of "one mile in January". Broadband ASE light source is widely used in high precision fiber optic gyroscopes. The low temporal coherence of the light source is conducive to improving the noise level and bias stability of the gyroscope. With further research, If the output power of ASE light source exceeds a certain level (The power detected by photoelectric detector greater than 10uw), it is found that the relative intensity noise(RIN) of the light source will be the main noise of the FOG. On the basis of studying the sources of fundamental noises (especially intensity noise) in high precision FOG, this paper puts forward the technology of suppressing the noise of high precision FOG, and further designs (large ring size and fiber length) and develops a prototype of high precision FOG with noise suppression technology. The test results of the prototype demonstrate the effectiveness of the suppression technique (for example, ALLAN variance comparison results before and after using suppression technique). The prototype of the accuracy is expected to approach the navigation accuracy of " one nautical mile in a month " through further testing in the FOG inertial navigation system.
The scale factor and other performance of high-precision fiber optical gyro(FOG) is directly related to the performance of the gyroscope using the Fiber source. High-precision fiber optic gyroscope with wide spectrum fiber source used to output spectral width and high power and get high mean wavelength stability. because the fiber gyro scale factor is calibrated by mean wavelength, the mean wavelength stability directly determines the stability of the scale factor of FOG, which is the mean wavelength stability that is the most important parameter in high precision fiber optic gyroscope with wide spectrum source. For erbium doped super-fluorescent fiber light source, the change of average wavelength is mainly due to the change of ambient temperature.
In this paper, based on the theory and concept of photonic crystal, an erbium doped photonic crystal fiber light source based on a double backwards structure is constructed, and the optical path and circuit driving scheme of the erbium doped photonic crystal fiber light source are designed. By optimizing the parameters of erbium-doped photonic crystal fiber, including the length of the erbium-doped photonic crystal fiber, the power loss and pumping power and so on, we finally get the prototype of the erbium doped photonic crystal fiber source. Through the experiment of the light source, the wavelength and the temperature correlation coefficient of the fiber light source reach 1ppm/ degrees.