High-precision Fiber Optic Gyroscope Research Articles

Tilted fiber grating polarizer in a 40-µm polarization-maintaining fiber.

The optical polarizer is a crucial component widely used in many optical systems and applications. Fiber-optic polarizers have the merits of excellent compatibility and ease of integration with other fiber components. We report an in-line polarizer enabled by a 45° tilted fiber grating inscribed into a specialty fiber for the next generation fiber-optic gyroscope, i.e.,a 40-µm ultra-fine-diameter tiger-type polarization-maintaining fiber with which the size of fiber-optic sensors can be miniaturized. The results show that a 40-mm-long polarizer operates at a center wavelength of around 830nm with high-performance characteristics, such as a polarization extinction ratio exceeding 30dB, a low insertion loss of less than 1.5dB, and a large 3-dB optical bandwidth more than 60nm. This kind of fiber-optic polarizer may have a broad scope across applications and systems such as fiber lasers and sensors, especially high-precision fiber-optic gyroscopes.

On-board Dynamic Measuring of Long-wave Track Irregularity based on Visual Inertial Fusion

This paper studies an inspection method to measure the long-wave track irregularities using the signals of IMU (Inertial Measurement Unit) and Laser & Camera installed on a bogie, which is implemented in comprehensive inspection trains. To reduce the influence of random noise and vehicle vibration, the mechanical structure is optimized; the spatial-dependent change of the "two-point chord" on the track is observed by high-precision FOC (Fiber Optic Gyroscope) and laser camera components; the angular velocity measurement method is deduced. To eliminate high-frequency attenuation of the signal, a sensor fusion algorithm based on the concept of complementary filters is presented. The angular velocity-based method is also used to measure low spatial frequencies, while the acceleration-based method is used to measure high spatial frequencies. The measurement accuracy of the system is evaluated from two aspects: internal and external coincidence accuracy. The test shows that the repeatability accuracy of the system to alignment and profile of the wavelength of 200 m is 0.5 mm and 0.8 mm, respectively, and the trend item and the line design value maintain good consistency.

A Multivariate Temperature Drift Modeling and Compensation Method for Large-Diameter High-Precision Fiber Optic Gyroscopes

A Multivariate Temperature Drift Modeling and Compensation Method for Large-Diameter High-Precision Fiber Optic Gyroscopes

Method for improving the polarization extinction ratio of multifunction integrated optic circuits.

The polarization extinction ratio (PER) of the multifunction integrated optic circuit (MIOC) is significant in maintaining polarization reciprocity in the fiber-optic gyroscope (FOG), and a high PER value is required, particularly in high-precision FOGs. Practically, the value of the PER decreases owing to the recoupling of the TM mode to the output port, thereby degrading the performance of the FOG. To improve the PER, the propagation of the leaking TM mode in the substrate is analyzed first. The variation of the PER with the chip structure is simulated based on the overlap integral algorithm of the optical mode. According to the analysis results, a structure of double absorption trenches at the bottom of the MIOC is proposed to block the TM mode from reflecting to the output port. In comparison with the traditional design, the optimized MIOC exhibits a higher PER that increases by approximately 25 dB and the average value of the PER reaches 75 dB. The MIOC design proposed in this study has good potential for application in high-precision FOGs.

Study on the High-Birefringence Hollow-Core Anti-Resonant Fiber with Semicircular Cladding

For the purpose of satisfying the demands of polarization-maintaining fibers for fiber optic gyroscopes, this article proposes a semicircular cladding birefringent hollow-core anti-resonant fiber. The influence of structural parameters on the birefringence, loss, and bending loss of the fiber is studied. The simulation results demonstrate that at 1550 nm, the ultimate loss of the fundamental mode of x and y polarization is 1.76 dB/m and 0.93 dB/m, respectively. The birefringence can reach 1 × 10−4, and the wavelength range of birefringence greater than 10−4 can reach 60 nm. This indicates that it has excellent bending properties. The proposed optical fiber has excellent performance in polarization maintenance and can supply ideas for the research of high-precision fiber optic gyroscopes and other optical devices.

A New Compressed-Structure-Based Coning Algorithm for Fiber Optic Strapdown Inertial Navigation Systems

For strapdown inertial navigation systems (SINSs) equipped with high-precision fiber optic gyroscope whose outputs are angular rate signals, the attitude calculation accuracies of traditional angular-rate-based rotation vector algorithms are limited when the vehicle is in a highly dynamic environment due to the fact that only the compensation of the second-order noncommutativity error is considered. Although the attitude algorithms based on polynomial iteration have higher accuracy, the computational complexity is too large. In order to fully tap the accuracy of the inertial measurement unit (IMU) to reduce the attitude errors, the third-, fourth-, and fifth-order Picard solutions for the equivalent rotation vector differential equation are derived in this article. A new method with a compressed structure to calculate the rotation vector for real-time processing systems is proposed to further reduce the noncommutativity error. In a classical coning motion environment, the frequency-series-based Taylor expansions are utilized for error analysis and design of the new algorithm’s coefficients. The effectiveness of the proposed coning algorithm with eighth-order accuracy is validated by digital simulation and initial alignment experiments in the turntable. In comparison with the traditional algorithms, the proposed algorithm improves the yaw alignment accuracy by 78.5%, the pitch alignment accuracy by 73.8%, and the roll alignment accuracy by 66.9% on average.

A Highly Integrated Automatic Fiber Optical Gyroscope Sensing Coil Winding System

Fiber optic gyroscope (FOG) is a new type of optical sensor used to measure the rotating angular velocity. As the core component, fiber optic coil (FOC) plays a decisive role in the FOG output precision. The manufacturing level and efficiency of FOC have been main factors restricting the application and development of high precision FOG. Precision mechanical positioning method based on the photoelectric devices was researched, and high-performance fully automatic micro mechanical error compensation technique was developed. On these basis. automatic fiber distribution and winding control technology were realized. Eventually a multifunctional system was developed with fiber splitting module, fiber winding module, and calibration module. This system could accomplish automatic preparation of FOC with quadrupolar symmetric pattern according to the parameters set by user. The principle and working flow of each functional module are discussed in details. Experiments show that the system can achieve automatic speed changing, automatic reversing, constant small tension control and precise fiber arrangement. The new designed system greatly improve FOC production efficiency and is conductive to promoting high level FOG development.

Application study of ultra high frequency modulation of laser radiation for fiber-optic gyroscope noise reduction

Microwave photonics is implemented in many applications, including the area of inertial navigation systems based on high-precision fiber-optic gyroscopes. Microwave photonic technologies allow increasing the fiber-optic gyroscope accuracy. This paper investigates and evaluates the effect of ultra high frequency modulation of laser radiation on the closed-loop fiber-optic gyroscope output signal. Research results show that ultra high frequency modulation makes it possible to broaden spectrum width due to redistribution to modulation harmonics of the laser radiation. This approach allows to reduce the standard deviation of the laser-driven fiber-optic gyroscope output signal more than 2.5 times compared to using a laser-driven fiber-optic gyroscope without modulation. In order to achieve the noise level of a laser-driven fiber-optic gyroscope the same as the noise level of a fiber-optic gyroscope with a broadband source, it is necessary to use a broadband noise source with a constant power spectral density and higher output power. This study is useful for understanding how application of microwave photonic technologies can impact on the fiber-optic gyroscope output signal. The obtained results can be used for researchers in this area of study and can facilitate the rapid development of this field.

High Precision Fiber-Optic Gyroscope Resolution Test Method Based on Low Precision Turntable

Aiming at the inability of low precision ordinary turntable to effectively measure the resolution of the high-precision fiber-optic gyroscope (FOG), this paper proposes a method for a high-precision FOG resolution test based on a low-performance turntable with the earth's angular velocity as the input value. Taking a two-axis turntable with 1 arc-minute angular precision as an example, the Two-Degrees-Of-Freedom (2-DOF) theoretical angle range is obtained, through stationary gyro biaxial angular position error incremental output analysis. The method can be used for high-precision FOG including, 0.001 deg/h, 0.0001 deg/h, 0.00001 deg/h (three typical accuracies) resolution measurements. The detailed test steps are presented. Simulation results show that traditional test methods fail under the same working conditions, while the proposed method can effectively measure the high-resolution gyro resolution effective coverage within the theoretical angle range of the corresponding two-axis turntable. Experimental results demonstrate that the two-axis turntable based on with 1 arc-minute angular precision can effectively perform a high-precision FOG resolution of 0.005 deg/h.

High thermal-stability Er-doped superfluorescent fiber source with a vertical cleaved fiber tail

Abstract Mean wavelength stability, a key indicator for evaluating the dynamic performance of Er-doped superfluorescent fiber source (ED-SFS) and high-precision fiber optic gyroscope (FOG), shows high sensitivity to environmental temperature fluctuations. In this paper, a thermally-stable ED-SFS in a one-stage backward configuration is proposed by incorporating a vertical cleaved fiber tail which acts as a Fresnel reflector. Our proposed method demonstrates a mean wavelength stability of 150 ppm and a scale factor error of 702 ppm. Comparing with alternative techniques such as Faraday rotator mirror (FRM) or fiber mirror (FM) over a 100 °C range (−40 °C to +60 °C), the wavelength stability and scale factor error are 105~120 ppm and 230~400 ppm less, respectively. The proposed ED-SFS has a spectral width (FWHM) of 37.682 nm and 10.42 mW output power, which satisfies the requirements of high-precision FOG.

小型化高精度光纤陀螺的检测电路串扰自检测

小型化高精度光纤陀螺的检测电路串扰自检测

Development and In Situ Application of Deformation Monitoring System for Concrete-Face Rockfill Dam Using Fiber Optic Gyroscope.

Deformation monitoring is of importance to ensure the operation status of concrete-face rockfill dams (CFRD). This paper reported a novel fiber optic gyroscope (FOG) monitoring system for continuously monitoring face slab deformation of CFRD, which consisted of a permanent monitoring pipeline and a sensing vehicle. The monitoring pipeline was made of steel pipes and polyvinyl chloride polymer connectors, which was embedded in a slot of the crushing-type sidewall beneath the concrete face slab of CFRD, forming a permanent monitoring channel. The sensing vehicle was equipped with a high-precision FOG sensor. A low-pass filter was designed to eliminate the vibration noise of the angular velocities of the sensing vehicle during the monitoring process. An in situ test was carried out on the Shuibuya dam, the highest CFRD in the world. The measurements of the FOG monitoring system agreed well with traditional instrument measurements, serving as validation of the system. The FOG monitoring system has the advantages of excellent repeatability, long service life, distributed monitoring, and automatic measurement.

The Application of High Efficiency and Low Noise Switching Power Supply in Fiber Optic Gyroscope

For high-precision fiber optic gyro systems, the efficiency and noise in the switching power source limits its application and also affects the system's light source and signal processing circuit, resulting in output errors. The interference mechanism of switching power supply ripple noise on super luminescent diode (SLD) light source and demodulation module in fiber optic gyro system is analyzed. A high-efficiency and low-noise switching power supply based on synchronous rectification is proposed. The power supply uses RC circuit to realize adjustable switching frequency. The push-pull isolation topology, LC filter and LDO regulator circuit are used to achieve constant voltage output with peak-to-peak ripple noise of less than 1mV. The conversion efficiency of the switching power supply is improved by 10%, which provides a high-quality power source for the high-precision fiber optic gyroscope. In the meanwhile, the switching power source for FOG is 541cm in size, which is beneficial to the miniaturization of inertial navigation system.

Suppression of the quantization error in a fiber optic gyroscope using a double-electrode-pair multifunction integrated-optic circuit.

The measuring accuracy of the fiber optic gyroscope (FOG) for weak signals under very short sampling time is significantly impacted by the quantization error, impeding its application in high-speed measurement and real-time control. In this work, we propose and implement a double-electrode-pair multifunction integrated-optic circuit (MIOC), which contains an additional pair of short electrodes besides the conventional electrode-pair. Taking advantage of the better modulating precision of the additional electrode-pair, the digital feedback is more refined and the quantization error in the FOG output is significantly suppressed. The driving circuits and the control scheme of the proposed MIOC are specially designed for FOGs. Experimental results show that the resolution for extremely small angular rates at short smoothing times is significantly improved. This work provides the potential of the applications in high-speed measuring and controlling systems for high-precision FOGs.

Temperature modeling of modulation phase error in the integrated optical chip for closed-loop interferometric fiber optic gyroscope

An integrated optical chip (IOC) is the phase modulation actuator in a closed-loop interferometric fiber optic gyroscope (IFOG). Research on temperature characteristic of IOC is meaningful for high-precision IFOG working in harsh environment. We focus on the temperature modeling of the IOC modulation phase error. In theoretical analysis, based on the temperature dependence of the IOC equivalent capacitance, a model between IOC modulation phase error and temperature is proposed. Through experiments, the variation tendency of the IOC equivalent capacitance with temperature is first presented. Subsequently, the IOC modulation phase error is demonstrated to be linear with temperature, which verifies the effectiveness of the proposed model. We provide an error research direction of IOC for high-precision fiber optic gyroscopes.

Angular random walk improvement of a fiber-optic gyroscope using an active fiber ring resonator.

High precision fiber-optic gyroscopes (FOGs) interrogated with broadband light have angular random walk (ARW) limited by the source relative intensity noise (RIN). A passive fiber ring resonator (passive FRR) reduces the RIN and improves the ARW, but the low power transmission results in a low signal-to-noise ratio at the detection. For a great ARW improvement, the fiber ring resonator should have not only a great RIN reduction but also a large power transmission. An erbium-doped fiber amplifier (EDFA) is inserted in the passive resonator to construct an active fiber ring resonator (active FRR). The EDFA compensates for the loss of the resonator and leads to a high finesse and a greater reduction in the RIN. The coupling ratios of the couplers in the active FRR are both 50%-50% tap. By adjusting the EDFA gain properly, a 17-dB decrease in the RIN is demonstrated, which reduces the standard deviation by 8.5dB. Adding the active FRR between the Sagnac interferometer and the broadband light, the detected power reaches 150μW with the FOG at rest and without modulation, which is about one hundred times of the detected power when using a passive FRR. The phase noise is reduced by 6dB at the proper frequency. The ARW is improved by 4.9dB from 1.40 to 0.45 mdeg/hour1/2.

Compensation for the temperature dependency of fiber optic gyroscope scale factor via Er-doped superfluorescent fiber source

Scale factor, as an important indicator for evaluating the dynamic performance of high-precision fiber optic gyroscopes (FOG), shows high sensitivity to the environmental temperature. Research on the temperature dependency of scale factor is meaningful to improve the robust performance and reliability of high-precision FOG. We theoretically analyze the sensitive factors, which could cause the scale factor error, and propose an effective method to compensate the scale factor via the temperature dependency of Er-doped superfluorescent fiber source. The experimental results show that, with our method, scale factor error can be reduced from 1185 to 640 ppm over 100°C temperature range (−40°C to 60°C).

New Scheme of Microlens for High-Yield Laser Coupling to PMF by Calibrated Glass Coating

A new scheme of oriented hyperboloid microlens (OHM) for high-yield lasers coupled to polarization-maintaining-fibers (PMFs) employing calibrated spin-on-glass (SOG) coating, automatic grinding, and electric field techniques is proposed. The results showed that the OHMs were precisely controlled to achieve the required minor radius of curvature of 4–4.9 $\mu \text{m}$ for achieving high-average coupling efficiency of 81.7% and high-average polarized extinction ratio of 31.5 dB from lasers to PMFs. In comparison with the fabricated OHMs by multiple fusing techniques, the SOG coating significantly reduced the fabrication time from more than 20 fusing times to a single time of electric field, decreased the average OHM offset from 0.59 to 0.47 $\mu \text{m}$ , resulting in the increased tolerance of the required radius of curvature of the OHMs from 4.0–4.2 to 4.0–4.9 $\mu \text{m}$ , and hence the OHMs with high-yield coupling efficiency to an average of 81.7% from laser to PMF. This is due to the OHM structure by SOG coating layer integrated with a uniform electric field to provide a simple process for adjusting the required minor radius of curvature. In addition, the OHM offset was minimized due to the balance of the electrostatic pulling force and the surface tension of the SOG liquid. The newly developed OHMs with unique SOG coating technique is beneficial for the applications of laser/PMF modules use in high-precision fiber optic gyroscopes as well as many low-cost and high-performance lightwave interconnection applications.

The application of low-noise DC-DC power source in fiber-optic gyroscope system

In high-precision fiber-optic gyroscope (FOG) system, the spike noise of DC-DC power source can lead to a considerable disturbance to the signal processing circuit of FOG, which results in a sampling error. In this work, the cause of spike noise and the influence mechanism were clarified. The slew rate control technology was researched and proved to be an effective solution to prevent spike noise of FOG power source. Using slew rate control technology, a kind of low-noise power module has been developed and applied successfully in the FOG system. This power module consists of DC-DC circuit and LDO circuit, and slew rate control circuit was used in the DC-DC circuit to realize low-noise performance. The peak-to-peak noise value of the developed power module was tested to be about 1 mV in a bandwidth of 200 MHz. Two typical FOG systems were tested with the use of this low-noise power source, and their output noise improvement were 3.1% and 4.4%.

In-Orbit Performance Evaluation of a Spaceborne High Precision Fiber Optic Gyroscope

An in-orbit experiment was launched to evaluate the performance of the spaceborne high precision fiber optic gyroscopes (FOG). The three-axis in-orbit data of the FOG were analyzed using wavelet analysis method. Features of low frequency period terms and glitch noise were demonstrated. In addition, a method to extract the random noise from the in-orbit data is proposed based on the first-order difference method and the Pauta criterion. In addition, the random walk coefficient (RWC) of the FOG was calculated with the Allan variance method. Compared the ground test results, the in-orbit performance evaluation of Spaceborne High Precision Fiber Optic Gyroscope was verified.