During the vibration process, the output of the gyroscope will add a non-zero offset small amount based on the Earth's rotational speed component, which is the output error term of the gyroscope vibration. When the gyroscope adopts two different closed-loop models, the error magnitude of the same gyroscope is different. Therefore, selecting an optimal closed-loop model while adjusting appropriate closed-loop parameters is crucial for solving the vibration problem of gyroscopes. Firstly, compare the differences and stability conditions between the two closed-loop models; Secondly, analyze the reasons for the error terms generated during the vibration process of the gyroscope and the reasons for the different sizes of error terms generated by different models; Then simulate and analyze the output of gyroscope vibration under different closed-loop models. The simulation and specific experimental results indicate that selecting an optimal closed-loop model shortens the closed-loop integration delay time of the model, and maximizes the closed-loop gain as much as possible while ensuring that there are no resonance peaks in the closed-loop amplitude frequency characteristic curve. This can reduce the output error term of the gyroscope and improve its dynamic performance.
Interferometric integrated optic gyroscope usually applies a square wave phase modulation signal, namely two state modulation or four state modulation, between two back-propagation light waves. The amplitude of square wave phase modulation is π/2, and the modulation frequency is the intrinsic frequency of the sensitive loop. Based on this unique demodulation method, it is inevitable to generate a spike pulse signal at the output signal end of the detector. This spike pulse signal can cause transient saturation in the front or rear amplifier of the detector, and signal distortion will occur when the detector recovers from this overload state; The asymmetry of peak pulses can generate odd harmonic interference coupled into useful signals, resulting in errors during demodulation and increasing the output noise of the gyroscope. Therefore, it is necessary to process the spike pulse. This article theoretically analyzes the reasons for the output noise of the gyroscope caused by spike pulses, and adopts a method to avoid the impact of spike pulses. Simulation shows that this method not only eliminates spike pulses, but also eliminates odd harmonic interference induced by spike pulses. The experimental comparison shows that this method significantly improves the accuracy of the gyroscope.
Process initial alignment and azimuth estimation algorithm is an important technology of the land vehicle Strapdown Optical Fiber Positioning and Orientation System (SOFPOS). The initial alignment of the vehicle is easily affected by the maneuvering environment such as turning and the noise of the odometer, especially when turning sharply, the alignment accuracy of the optical fiber system will be reduced. Firstly, this paper analyzes the principle of odometer lever arm error and the measurement compensation method in the SOFPOS. A comprehensive physical model based on the longitudinal lever arm and the left and right lateral lever arms is proposed, and the odometer lever arm error model is also simulated. Then, the lever arm error is estimated by Kalman filter, and the odometer lever arm error is compensated. Finally, the compensation is applied to the initial alignment and azimuth estimation algorithm during the journey, and the experimental verification is completed by combining the hardware-in-the-loop simulation. The test results show that the alignment accuracy and positioning accuracy of the positioning and orientation system can be effectively improved by estimating and compensating the error of the odometer lever arm, and the environmental applicability of the land vehicle optical fiber positioning and orientation system can be improved.
With the rapid growth of the demand for various unmanned platforms, such as small Unmanned Aerial Vehicles (UAVs), small Autonomous Underwater Vehicles (AUVs), Unmanned Underwater Vehicles (UUVs), and driverless vehicles, the miniaturized, integrated, and large-scale production of interferometric Fiber Optic Gyroscopes (FOGs) and the fiber-optic inertial navigation have become an important research field. This paper first introduces the research status of integrated chip gyroscope, and then designs a miniaturized interferometric integrated optical gyroscope based on silicon lithium niobate thin waveguide, focusing on the structural design of silicon lithium niobate thin waveguide. The high efficiency microwave/light wave interaction problem of silicon lithium niobate thin waveguide electro-optical modulation is solved, the volume of optical modulator is significantly reduced, and the half wave voltage of optical modulator is reduced. Polarized waveguide is added to realize the function of traditional lithium niobate waveguide modulator. Finally, due to the stable chemical properties and high hardness of lithium niobate material, it is difficult to process it with conventional silicon waveguide etching process. This paper has conducted a preliminary study on its low loss processing technology. Although the silicon lithium niobate thin waveguide can significantly reduce the volume of the FOG and improve the integration of the FOG, due to the large gap between the size of the thin waveguide and the single-mode fiber core, if the direct alignment coupling is inevitable, a large coupling loss will be introduced. It is necessary to further study the low loss optical coupling technology of silicon lithium niobate to meet the requirements of miniaturized and integrated FOG.
High Precision Fiber Optic Gyroscope (HPFOG) is widely used in aviation, navigation, aerospace and other fields. Its development is of great strategic significance to a country's industry, national defense, science and technology. High precision fiber optic gyroscope usually uses a wide spectrum ASE light source to suppress the non heterotropic noise caused by Kerr effect. The gyro accuracy has been greatly improved. It has been reported that high-precision gyroscope reaches the reference level (ppm °/h). Compared with the laser gyro, the scale performance of the fiber optic gyro is still far from that of the laser gyro. The high-precision long endurance inertial navigation system has high requirements on the scale factor performance of the gyro. The scale error of the fiber optic gyro severely limits its application in the high-precision long endurance inertial navigation. The average wavelength of the light source is the main factor affecting the scale stability of the fiber optic gyroscope. This paper studies a double pass broadband ASE light source with real-time wavelength adjustment. By adding reflective light reflectivity control devices on the basis of the traditional reflective double pass broadband light source, the real-time accurate adjustment of the light source wavelength is realized, and then the scale factor of the high-precision fiber optic gyroscope is compensated and controlled to effectively improve the stability of the scale factor.
High-Precision Fiber Optic Gyroscope (HPFOG) is the core sensor of the long-endurance fiber optic inertial navigation system. The improvement of the positioning accuracy of the inertial navigation system depends on the improvement of the bias performance and the scale performance of the gyroscope. The broadband ASE light source can effectively suppress the noise such as Kerr effect and Rayleigh scattering in the optical path of the FOG. The flatness of the output spectrum of the ASE light source also affects the scale of the FOG. In this paper, the influence of broadband fiber light source on the bias performance and scaling performance of HPFOG is analyzed theoretically, and the design of a high-flatness C+L band broadband ASE light source is developed. By analyzing the conditions of the output spectrum of the ASE light source from the C-band to the L-band until the C+L band is formed, the pump light power and the length of the erbium-doped fiber are optimized, and the output spectral width, power and spectral flatness of the ASE light source are simultaneously improved. Performance, the developed C+L band broad-spectrum ASE light source has a spectral width of 80nm and a flatness of less than 1.5dB. Subsequently, this paper compares the performance of HPFOG using traditional Gaussian ASE light sources and high-flatness C+L band light sources. The experimental results show that although the spectral symmetry of the C+L band broad ASE light source is weaker than that of the Gaussian spectrum ASE light source, but the scale factor performance of HPFOG is similar, and there is no obvious impact. The key is that the use of high-flat C+L band broad ASE light source significantly improves the bias stability of HPFOG. The normalized index shows that the 100s bias stability is improved by 30%.
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.
As high-precision fiber optic gyroscopes, especially three-axis high-precision fiber optic gyroscopes, face harsh electromagnetic environments, Y-junctions have become a key component that affect the precision of fiber optic gyroscopes. A high extinction ratio Y-junction is fabricated to suppress the polarization mode coupling of the fiber optic gyroscope and reduce the noise of the fiber optic gyroscope. The experimental results show that the above methods effectively solve the effect of the deterioration of the precision of the fiber optic gyroscope caused by the Y-junction.
With the change of working time and environmental conditions, the performance of optical fiber coil has deteriorated, which seriously affects its long-term stability. In recent years, the performance of fiber optic gyroscope(FOG) has been continuously improved, and the requirements for adhesive of fiber optical coil have become higher and higher. It is required not only to meet the stability of coil potting, but also to resist high and low temperature environment for a long time during operation of FOG. In view of this, the study in the environmental stress effects of optical fiber coil adhesive was carried out. Based on optical fiber coil, this paper introduces the environmental stress and its influence mechanism of polymer materials aging, and focuses on the optical fiber coil adhesive aging behavior, as well as analyses the physical and chemical properties of adhesive. On basis of this, environmental stress tests were carried out, and the physical and chemical properties of adhesive were obtained. The experiment and analysis results showed that the glass transition temperature will significant transfer under excessive ultraviolet exposure or a long time high temperature of 85degree Celsius and low temperature of -45degree Celsius, and the adhesive viscosity significantly increased in high humidity environment. Under the comprehensive effect of various environmental stress, the adhesive properties will changed and further affect the stability of optical fiber coil.
Compared with laser gyroscope, it is still difficult for the scale factor stability of high-precision fiber optic gyroscope (FOG) to achieve better than 1ppm under variable temperature conditions due to the influences of the fiber coil and the light source. We proposed to add multiple precision temperature measuring devices to the fiber coil, and established a multi-modulus temperature compensation model by measuring the temperature at multiple locations of the fiber coil. The stability of the FOG scale factor is greatly improved.
With the rapid development of the fiber optical gyroscope technology and its widely applies, the multi-axis Fiber Optical Gyroscope (FOG) such as the triaxial FOG and its system are popular more and more.[1-2] For the requirement of less weight and less size,[2] the multi-axis FOG needs higher electromagnetic structure design skills and more critical devices compared with uniaxial FOG. The Z axis of some triaxial FOGs occur the problem of the bias instability over tolerance, which is a real engineering case in our development process. In this paper experiments are carried out after the influence factors are analyzed. Results show that the modulation of the Z axis is interfered by the other two axes. There are three test steps in the experiment including the optical unit test, the modulator test and the modulator shield test with different materials. A simulation of the original shield structure is applied in order to find the structure defects. Two defects are found on the base of the analysis of the electromagnetic structure check. The main defect is that there is a hollow structure on the top of the Z axis in the system which causes extra electromagnetic circuit from the other two axes. The other defect is that each axis is exposed under complex circumstance with less modulator shield. The modulator with less shield has the merit of less thermal stress owing to the free contraction between the metal packaging and the modulator. In our triaxial FOG system, the modulator shield structure inherits from the uniaxial FOG with less shield, in order to decrease the thermal stress. As we know, in the uniaxal FOG the modulator will still robustly work under a clean electromagnetic circumstance, even there is no shield upon the modulator. However, in the multi-axis FOG there are obvious crosstalk interference between the different axes, when all axes are working together with a close frequency. Based on the experiments and the analysis, the following design principles are given. Firstly, the thermal factors, the vibration factors and the electromagnetic factors should be considered at the same time when the modulator shield is designed. Secondly, the Fe-Ni material has better shield effect than the common metal like Aluminum. Thirdly, there are two kinds of resins, the hard buffer and soft buffer, to connect the Y-junction fiber tail and the metal capsulation. This paper is of great use to the engineering of the multi-axis fiber optical gyroscopes and the fiber optical gyroscope system applications.
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.
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 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.
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.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.