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In this study, a novel freeform surface lens coupler is designed to realize the coupling functions in the hollow‐core photonic crystal fiber (HCPCF) resonator optical gyroscope. One surface of the lens is an ellipsoid. Coupling of the two HCPCF loop's ports can be directly accomplished via reflection on the ellipsoid surface. The other surface of the lens is the Biconic Zernike surface. Transmitting through the above two surfaces, the coupling between the intracavity and extracavity is completed. In this paper, simulations were performed based on two types of HCPCFs, a hollow‐core photonic bandgap fiber of HC19‐1550 and a state‐of‐the‐art nested antiresonant nodeless fiber. The volume of the lens coupler is calculated to be approximately 4 × 2 × 4 mm3. The simulation results show that the intracavity coupling loss can be as low as 0.011 dB, and the coupling loss between the intracavity and extracavity can be as low as 0.4 dB. Compared with the traditional fusion scheme between hollow‐core fiber and polarization‐maintaining fiber, the freeform surface lens coupler in this paper can achieve lower coupling loss and higher resonance fineness. Compared with other spatial coupling schemes, it has lower coupling loss and fewer coupling components. [ABSTRACT FROM AUTHOR]

Abstract A novel special optical fiber, which is very sensitive to magnetic field, is proposed. The two beam lights counter-propagating in this kind of fiber can generate large nonreciprocal phase shift. It can be used in ultra-low magnetic field detection. In this paper, the related theory is derived in detail. The influence of fiber parameters on the effect is simulated and analyzed. It is proved that a magnetic field sensor with pTesla-level precision could be demonstrated with this kind of special fiber in this paper. [ABSTRACT FROM AUTHOR]

• The effect of angular vibration on FOG is studied. • The amplitude frequency characteristics of FOG under dynamic conditions is considered. • The bandwidth test experiment is utilized to verify the effectiveness of our method. • Our method can effectively compensate the dynamic error in angular vibration environment. The fiber optic gyroscope (FOG) is an angular rate sensor based on Sagnac effect. It has been widely used in aviation, unmanned, robot, and other fields due to its benefits of all solid state, high precision, and low cost. However, the photoelectric devices inside the FOG will produce a non-negligible error in the dynamic environment, resulting in zero bias drift and increased noise. Currently, research on the dynamic error of FOG focuses primarily on linear vibration, assuming that no input angular rate exists at this moment. However, the dynamic errors caused by angular vibration are more complicated in the practical application environment. The output of FOG includes both effective angular information and dynamic error at this moment, which means that the dynamic error should be removed while the effective angular information must be retained. In this paper, we focus on the effect of angular vibration on FOG, and propose a dynamic error compensation method of FOG based on complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) that properly separates the effective signal and dynamic error. We also consider the amplitude frequency characteristics of FOG under dynamic conditions and utilize the FOG bandwidth test experiment to verify the effectiveness of our method. The experimental results show that the compensated signal can correctly calculate the bandwidth of FOG. It indicates that our method can effectively compensate the dynamic error in angular vibration environment while improving the performance of FOG in dynamic environment. [ABSTRACT FROM AUTHOR]

• The coupling effect of input velocity and temperature is considered. • A new fast calibration method is established. • LSTM is used to comepensation the nonlinear error. • The calibration time is shortened by 30% while the angle measurement error is reduced by 70%. The calibration accuracy of the inertial navigation system (INS) has a non-negligible effect on its actual navigation performance. As the core component of the INS, the scale factor error of the fiber optical gyroscope (FOG) is one of the main error sources of the INS, which has a vital impact on the navigation accuracy. Generally, the scale factor of FOG is considered to be a constant value, but with the increasing demand for the accuracy of FOG, the scale factor error can not be ignored, how to calibration the FOG scale factor at different input velocity rates and temperature has attracted people's attention. The traditional calibration methods usually select several fixed temperature points and input velocity points, then the scale factor error is compensated by linear fitting or piecewise fitting. In order to improve the calibration accuracy, our paper considers the coupling effect of input velocity rate and temperature and designs a calibration experiment at continuous input velocity rates and temperature, the calibration time is shortened by 30%, then we propose a nonlinear error compensation method based on the LSTM. The experimental result shows that the std error of the FOG scale factor is reduced from 280 ppm to 13 ppm and the angle measurement error is reduced by 70%, which verify the effectiveness of our method. [ABSTRACT FROM AUTHOR]

Based on the principle of multimode interference (MMI) imaging, an MMI waveguide reflector with high reflectivity, high bandwidth, and high process tolerance is designed using a lithium niobate thin film. The simulation results show that when the input light is transverse electric (TE) polarized, the maximum reflectivity of the designed MMI waveguide reflector is 96.5% at the working wavelength of 1.55 μm, and the bandwidth is 110 nm with more than 90% reflectivity. We also designed an experiment to measure its reflectivity. The experimental result of reflectivity is 85.24%. Compared with other proposed waveguide reflectors, it has the advantages of high reflectivity and large bandwidth. These results indicated that this optimized waveguide reflector design can be applied to integrated optical system based on lithium niobate thin film. • We obtain the optimal structural parameters of the waveguide reflector. • MMI waveguide reflector has high reflectivity and large bandwidth. • Increasing the bending radius can further improve the reflectivity. • It can provide flexibility for device design on lithium niobate thin film. [ABSTRACT FROM AUTHOR]

In this work, a transverse magnetic (TM)-pass polarizer based on subwavelength grating (SWG) on the emerging potential hybrid silicon-LNOI platform is proposed. By integrating silicon material onto the LNOI platform, the optical power of TE0 and TM0 modes is judiciously distributed to distinct regions. This design not only effectively blocks the TE0 mode but also enables low-loss transmission of the TM0 mode, thereby achieving a balanced manipulation of both polarizations. Due to the strong reflection of TE0 mode by SWG, a polarizer is realized with a high polarization extinction ratio (PER) and low insertion loss (73 dB and 0.37 dB respectively at 1550 nm) in a compact size (device length is 23.38 μm). Moreover, the PER is beyond 50 dB and the insertion loss is under 0.46 dB in a broad wavelength range of 1525 to 1585 nm. [ABSTRACT FROM AUTHOR]

We theoretically analyze the performances of the anti-PT-symmetric gyroscope near the exceptional point (EP). The results show that the frequency splitting caused by rotation is proportional to the square root of the fraction of power coupled from the bus to the ring. To fully exploit the potential of the EP, one needs to overcome two aspects of challenges. The first one is the preparation of sensitive unit, to detect the angular velocity of 104 deg / h with a micron-scale sensor; the allowable variation in the ratio of cavities' radii is within the order of 10 − 16, which is exceedingly challenging in current nano fabrication. The other is controlling environmental disturbances. A temperature variation of 0.002°C would make the minimum detectable rotation rate up to 1010 deg / h, which is far beyond practically applications. Our analysis points out the difficulties in realizing this gyroscope, which has significant referential values to future work. [ABSTRACT FROM AUTHOR]

• The fiber optic gyroscope (FOG) is adopted to dynamic angle measurement. • The error compensation model based on tilt sensor is established and the compensation scheme is designed. • Validity and feasibility verification is carried out by some simulation and the experiments based on the instrument prototype. The fiber optic gyroscope (FOG) has been widely used in the field of dynamic angle measurement due to its characteristics of wide dynamic range and high precision. Considering the change of the installation state of the FOG and the inconvenience of the calibration of the scale factor in engineering, an error compensation of the angle measurement using FOG, which is based on the tilt sensor, is proposed in this paper. Firstly, the principle of the angle measurement based on the FOG and the principle of the tilt sensor are introduced and the error compensation model based on tilt sensor is established. Secondly, simulation analysis and error analysis are performed and the compensation scheme is designed. Finally, according to the compensation scheme, the instrument prototype is built and the experiments are carried out. The experimental results show that although the error is not completely eliminated after adopting compensation scheme, the angle measurement deviation of the FOG can be greatly reduced and limited within 5″ when the tilt state changes within a small range (the output of the tilt sensor is less than 0.3°). It indicates that the compensation scheme is effective and feasible. More importantly, it is easier to realize in engineering in contrast with other compensation methods. [ABSTRACT FROM AUTHOR]

In this paper, we present a full description of the design and fabrication of a compact spot-size converter (SSC) applied to interferometric fiber optic gyroscopes (IFOGs). The obtained SSC has a length of 500 um and a coupling efficiency of 52%. The polarization dependency of the SSC is less than 0.1 dB, and the variation tendencies of our experimental results agree well with a simulation. The SSC possesses many properties suitable for various optical communication and sensing systems, including small size, high coupling efficiency, integration, and high stability. [ABSTRACT FROM AUTHOR]

Dynamic angle measurement (DAM) is a research hotspot in the fields of aircraft, automobile and navigation. Using fiber optic gyroscope (FOG) to measure the dynamic angle has the advantages of high theoretical accuracy, all solid state and high reliability. In this paper, we propose a performance evaluation system for DAM of FOG based on a high accuracy single-axis rotary table. Besides, in order to solve the problem of multi-path signal synchronization, we propose an algorithm for signal delay measurement. As the experimental results show, the accuracy of the FOG proves to be less than 0.002° while it was 0.06° before synchronization compensation. The facts mentioned above provide the feasibility of achieving good real-time DAM with high accuracy and wide dynamic response. [ABSTRACT FROM AUTHOR]

Software compensation is an effective method for enhancing the magnetic field environment adaptability of light-small fiber-optic gyroscope (FOG). In order to decrease the magnetic drift of FOG, an accurate magnetic sensor is typically required to measure the intensity of magnetic field in this software compensation method. The magnetic sensor generally suffers from the measurement error due to the variety of temperature. In order to compensate the magnetic drift of FOG preferably in full temperature range (−40 °C to +60 °C), the temperature sensitivity of the Hall sensor manufactured by Allegro is studied in this paper. Temperature compensation models of quescent voltage output and magnetic sensitivity are established, and the variation is compensated respectively. The measurement precision of Hall sensor is 0.02 G over the temperature from −40 °C to 60 °C after compensation, which meets the requirement of magnetic drift compensation of FOG in full temperature. [ABSTRACT FROM AUTHOR]

We propose a monolithic integrated cavity optomechanical accelerometer based on push-pull photonic crystal zipper cavity. The accelerometer integrates grating couplers, phase modulators, acceleration sensing unit, and electrostatic force feedback module on a chip. We use push-pull structure to eliminate the coupling crosstalk caused by paraxial acceleration and extend its range using electrostatic force feedback module. The transmissive photonic crystal zipper cavity structure is adopted to improve the integration and stability of the system. Accurate results are demonstrated as follows: the bandwidth is larger than 20 kHz, the mechanical sensitivity is 369 pm/g, the measuring range is ±100 g, and the noise equivalent acceleration is 5.06 μg / Hz. With its advantages, the accelerometer can be used in consumer electronics, aerospace, resource exploration, and other fields. [ABSTRACT FROM AUTHOR]

• Analyzing the uneven temperature field of the FOG in the start-up stage. • Proposing a novel compensation method of the scale factor error based on GWO-GRU. • Proposing a new calibration experiment for modeling the scale factor error in the start-up stage. The fiber optic gyroscope (FOG) is the core component of the inertial system, which has been widely utilized in aviation, maritime, automotive, and other fields. The scale factor is one of the critical parameters to characterize the dynamic performance of the FOG. Due to the temperature sensitivity of the optoelectronic devices, the scale factor errors will be caused with the temperature change. The traditional compensation method usually compensates the output of the FOG in a stable working state. Without considering the difference between the characteristics of the FOG in the start-up stage and the stable working state, the compensation accuracy of the traditional method cannot meet the demand for quick start-up in application areas. According to the above analysis, a novel scale factor error compensation method based on the grey wolf optimization (GWO) and gated recurrent unit (GRU) neural network is proposed in this paper. Furthermore, a new experiment is designed to calibrate the scale factor error in the start-up stage, which can reduce the calibration time and ensure the calibration accuracy. The experimental results demonstrate the proposed method significantly improves the compensation accuracy compared with other methods, such as the multilayer perceptrons (MLPs) and the traditional GRU network. [ABSTRACT FROM AUTHOR]

• The crosstalk influence between the different cores in MCF on IFOG is analyzed and relevant experiment is designed. • By connecting four cores of a 300-m long MCF as fiber coil of IFOG, the ARW is 0.006°∕√h and the drift is 0.01°∕h, which is close to the performance of SCF with the same length. • Closed-loop scheme and DSP are used. This scheme is expected to put MCF into the products of IFOG in the foreseeable future. In this paper, multi-core fiber (MCF) is integrated in interferometric fiber optic gyroscope (IFOG) as the sensing coil to improve its sensitivity without increasing the fiber length or Shupe error. We have used a 300-m long 7-core fiber and connected 4 cores of MCF to each other by fan-in and fan-out (FIFO) devices of fused taper in closed-loop IFOG to replace the traditional single-core fiber (SCF). Before experiment, the main benefits and certain possible problems of using MCF are explained and analyzed. The angular random walk (ARW) of 0.006°/√h and drift of 0.01°/h have been achieved, which is close to the performance of IFOG using the 1200-m long SCF. Besides having a lower Shupe sensitivity, the MCF-IFOG also has small crosstalk effect when using broadband light source. The results show that the scheme of MCF for IFOG is expected to be used in practical application in the foreseeable future. [ABSTRACT FROM AUTHOR]

Abstract A method of reducing the relative intensity noise (RIN) using a fiber ring resonator to improve the angular random walk (ARW) of a fiber optic gyroscope (FOG) is demonstrated. The RIN at the proper frequency f p degrades the ARW of the FOG when the detected power reaches tens of microwatts. Adding a fiber ring resonator between the source and the interferometer periodically modulates the optical spectrum and consequently reduces the RIN at f p. The reduction in the RIN is analyzed theoretically and experimentally. An experiment demonstrated a 5.2-dB decrease in the RIN at f p , which reduces the standard deviation by 2.6-dB. The ARW was reduced from 870 to 580 μ deg/h 1∕2 , which amounts to a 1.8-dB reduction. Highlights • A fiber ring resonator modulates the optical spectrum and reduces the relative intensity noise at FSR/2. • An experiment demonstrated a 5.2-dB decrease in the RIN at fp, which reduces the standard deviation by 2.6-dB. • The ARW was reduced from 870 to 580 μ deg/h 1 ∕ 2 , which amounts to a 1.8-dB reduction. [ABSTRACT FROM AUTHOR]

• • The startup state and stable working state of FOG are modeled independently. • • The temperature field is constructed by the built-in thermometer of six inertial sensors. • • GSA-SVR is used to compensate the temperature drift of SINS. • • Compared with traditional method, the navigation accuracy increased by more than 50%. The fiber strapdown inertial navigation system (INS) has been widely utilized in aircraft, autonomous driving, robotics, and other fields due to the rapid growth of fiber technology. The core components of INS, the fiber optic gyroscope (FOG) and quartz flexible accelerometer (QFA), are prone to affected by the environmental temperature variation. The traditional temperature drift compensation method requires a considerable time to calibrate each inertial sensor individually. But after the six inertial sensors are integrated, the temperature environment inside the INS will become more complex. As a result, this device-level method has an unsatisfactory effect in the practical application of INS. Furthermore, the traditional method ignores the fact that the temperature drift characteristics of FOG are not the same at different working states. To solve the above problems, we propose a novel temperature drift compensation method of INS based on gravitational search algorithm (GSA) tuning support vector regression (SVR). The startup state and stable working state are modeled independently based on the FOG's features. Without adding additional thermometers to the inertial sensors, the temperature field is constructed by making full use of the information provided by the built-in thermometer of six inertial sensors. The experimental results verify the effectiveness of our method during different working states. And compared with the traditional polynomial fitting method, our method has better performance in the navigation experiment, the navigation accuracy increased by more than 50%. [ABSTRACT FROM AUTHOR]

A magnetic drift that linear to orthogonal magnetic field (OMF) is induced by OMF which is parallel to the sensitive axis of the depolarized FOGs. As winding a fiber coil causes the refractive index near the center to increase and away from the center to decrease, by placing a short segment of special fiber at the end of the coil, the magnetic drifts induced by OMF in the special fiber and that in the single-mode fiber (SMF) are equal in magnitude but opposite in signs, which means the summation of the two magnetic drifts is zero. Therefore the goal of compensating magnetic drift induced by OMF in depolarized FOG is successfully achieved. [ABSTRACT FROM AUTHOR]

We put forward a theory that the magnetic field vertical to the sensing coil plane may induce a nonreciprocal phase error (NPE) in twin depolarized interferometric fiber optic gyroscopes (TD-IFOGs). A related mathematical model is established. The simulation analysis and experimental result show that the magnetic field error induced by a vertical magnetic field in a TD-IFOG is relatively stable. The error arising from the bending of the fiber is closely related with the radius of an optical fiber coil, fiber’s diameter, fiber’s length, the strength of the vertical magnetic field and so on. And as for a manufactured TD-IFOG, the vertical magnetic error is proportional to the magnitude of the vertical magnetic field. [ABSTRACT FROM AUTHOR]

A novel system structure of resonant fiber optical gyroscope using a parallel double hollow-core photonic crystal fiber ring resonator is proposed, which employs the double closed loop and reciprocal modulation–demodulation technique to solve the problem of the length mismatch between rings. This structure can suppress the residual amplitude modulation noise and laser frequency noise, essentially eliminating the influence of the Rayleigh backscattering noise and dramatically reduce the Kerr-effect-induced drift by three orders of magnitude. Thanks to its excellent noise suppression effect, the sensitivity of this novel system can approach the shot-noise-limited theoretical value of 8.94 × 10−7 rad/s assuming the length of the fiber ring resonator is 10 m. [ABSTRACT FROM AUTHOR]

• The RFOG simulation system is established, through which the relationship between resonance splitting and modulation frequency is obtained. • The resonance splitting is then explained based on sideband spectrum theory. • The feasibility of the sideband frequency locking technology is verified by resonance splitting based on sideband spectrum theory. In this study, the sinusoidal phase modulation and demodulation principle in resonant fiber optic gyro (RFOG) are introduced. The RFOG simulation system is established, through which the relationship between resonance splitting and modulation frequency of dual-frequency sawtooth and sinusoidal signal is obtained. The resonance splitting is then explained based on sideband spectrum theory. The experimental device is built and the results show that there are obvious resonance splitting and distortion in linear region of demodulation output, when the sinusoidal frequency is higher than FWHM /2. Finally, the feasibility of the sideband frequency locking technology is verified by resonance splitting based on sideband spectrum theory, providing theoretical support for this novel technology, which can suppress backscattering noise effectively. [ABSTRACT FROM AUTHOR]

We investigated the nonreciprocity induced by an orthogonal magnetic field (OMF) in a single-mode fiber coil and expressions for the propagation constant of light waves in the bent fiber are deduced. Coils with different radiuses are put into depolarized interferometric fiber optic gyroscopes (D-IFOGs) for experimental verification. Theories, simulations and experimental results show that the OMF induced nonreciprocal phase error is closely related to the bending radius and the generated magnetic drift in D-IFOGs is linear to the amplitude of the OMF. [ABSTRACT FROM AUTHOR]

In a resonant fiber optical gyroscope (RFOG) system, the imperfection of light intensity is primarily categorized into two parts: intensity fluctuation and inconsistent power of two paths. Firstly, the error of the intensity fluctuation effect on the RFOG scale factor is presented and simulated. Secondly, the RFOG bias drift caused by the Kerr effect is simulated when the intensity fluctuates. Next, an RFOG system with the servo of intensity stable is proposed. Experimental results confirm that the intensity fluctuation of the two paths is effectively suppressed, and the Kerr effect error can be effectively eliminated. Finally, the light intensity stability improves more than 30 dB, the RFOG bias stability decreases at least 6 dB, and the scale factor nonlinearly is suppressed by 20 dB. [ABSTRACT FROM AUTHOR]

The feedback parameter of closed-loop fiber optic gyroscope (FOG) in various engineering applications is discussed. It has been proved that unreasonable feedback parameter will cause great interference and serious distortion to the output signal. Therefore, we build a concise feedback control mode and obtain optimal range of feedback parameter. For different input signals concerned which nearly include all of the application scenarios in practice, detailed simulations and experiments are completed. The results show that the feedback parameter should be small in static applications and moderate for high response requirements. What is more, it should be relatively small when used in low-bandwidth measurement fields to ensure the response performance of low frequency signal and suppress high frequency noise and vice versa. This work plays an important guiding role for related parameter setting in the feedback control system of sensors, especially for gyroscope. [ABSTRACT FROM AUTHOR]

• Laser frequency drift characteristics, such as fluctuation range and frequency, influence the performance of the closed-loop frequency-locked module. • A novel measurement system is proposed, based on the Fabry–Pérot cavity and sinusoidal modulation of cavity length and demodulation by LIA. • This measurement scheme can be applied in other fiber sensor systems to evaluate the effect of laser frequency stability. In this study, to measure the frequency drift characteristics of the narrow-linewidth laser, we provide a method with high accuracy and adjustable measuring range that can be applied in a resonant optical gyro (ROG) system. In an ROG system, the laser frequency drift characteristics, such as fluctuation range and frequency, influence the performance of the closed-loop frequency-locked module. To measure the above performance of the laser, we proposed a novel measurement system based on the Fabry–Pérot cavity. We proved the feasibility of the scheme through theory and simulation. Then, the calibration of the experimental device and the measurement of the tested laser were completed. The measurement accuracy of this method is 1.2 kHz, and the measurement range reaches ±60 MHz, which can be adjusted by the modulation index. The results show that the laser has a frequency fluctuation of 30 MHz in the stabilization stage, and there is mainly a low-frequency component under 5 Hz in the frequency domain of the laser frequency fluctuation. Furthermore, this measurement scheme can be applied in other fiber sensor systems to evaluate the effect of laser frequency fluctuation on system output performance. [ABSTRACT FROM AUTHOR]

Abstract: An orthogonal magnetic field vertical to the light propagating direction will initiate a nonreciprocal phase drift in a depolarized interferometric fiber-optic gyroscope (D-IFOG). This drift appears a linear correlation to the magnitude of the orthogonal magnetic field. We proposed a software-compensation method by attaching two differential Hall sensors to the D-IFOG to sample the magnetic field in real time and the experimental results showed a notable improvement to the magnetic stability. [Copyright &y& Elsevier]

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. [ABSTRACT FROM AUTHOR]

Previous studies have shown that there exists a large nonreciprocal phase error in the single-mode fiber coil of a depolarized interference fiber optic gyroscope (De-IFOG) under time-varying temperature and magnetic field, which evidently weakens its environmental adaptability. A real-time software compensation method considering the coupling effect of time-varying temperature and magnetic field is first proposed and verified experimentally. After compensation, the error of De-IFOG decreases from 50 deg / h to 6 deg / h when the magnitude of the magnetic field is 10 G and temperature uniformly increases from 10°C to 60°C with time-varying rate of 36 ° C / h. The compensation method is of great significance in De-IFOG engineering applications. [ABSTRACT FROM AUTHOR]

• The measurement error of D-IFOG caused by vibration is discussed. • The optical transmission model of D-IFOG is established. • The stress distribution of D-IFOG caused by vibration is simulated based on finite element method. • A new high-precison angular measurement system is set up to evaluate the output error of D-IFOG. In this paper, we accurately obtained the depolarized interferometric fiber optic gyroscope (D-IFOG) output error caused by elasto-optic effect in vibration environment. We established the optical transmission model of D-IFOG and simulated the stress distribution of D-IFOG caused by vibration based on finite element method. The computational results show that the angular velocity error has a phase difference of 90° with the sinusoidal excitation, and when the vibration's amplitude is 4 g and the frequency is 70 Hz, for triaxial D-IFOGs, the maximum angle error of Y-axis is up to 3.54 × 10−4°, and that of X-axis and Z-axis is 6.26 × 10−5°. And we set up a high-precison dynamic angular measurement system based on dual-laser Doppler vibrometers to evaluate the angular error in D-IFOGs. The experimental results are consistent with those of numerical simulations, which have verified the angle error model. This work is meaningful for the follow-up D-IFOG's vibration error compensation. [ABSTRACT FROM AUTHOR]

• It is innovative that the alignment method is obtained by theoretical derivation. • Experimental system has been set up which could be put into use. • It can be seen that the alignment method is simple and accurate. For making alignment technology of PANDA polarization maintaining fiber (PMF) more efficient, we propose a method based on Polarization Observation by the Lens-effect Tracing (POL) through complete theoretical derivation for the first time in this field of study. The mathematical model of imaging is created by conducting the ray equation of light transmitting in fiber and we can achieve polarization alignment by means of adjusting position of the brightest fringe on receiving screen. Some alignment errors outside the method itself are also analyzed to eliminate. Additionally, experiments were designed and carried out to measure the alignment accuracy and indicated that our method is valid for it can achieve the accuracy of polarization alignment <±0.1 deg. The method can also be used to detect the fusion angle of optical fiber. [ABSTRACT FROM AUTHOR]

• The scale factor, which the output of the fiber optic gyroscope (FOG) is proportional to, is sensitive to many factors in engineering. • When the scale factor used fluctuates during the angle measurement process, it will bring an error to the angle measurement results. In this work, we analyzed the error caused by the scale factor instability of the FOG in engineering and proposed a real-time calibration scheme for the scale factor of the FOG based on self-collimator during the process of angle measurement. • Experimental results show that the angle measurement error can be kept stable and in a high precision for a long time by adopting the scheme. • Compared with other calibration or compensation methods on the scale factor, the real-time calibration method based on the self-collimator described in this paper is simpler, more feasible, and more convenient. • Also, the method doesn't need complex calculations or make optimizations in the structure and performance of the FOG. Thus, this method is more suitable to apply in engineering and easy to realize. The scale factor, which the output of the fiber optic gyroscope (FOG) is proportional to, is sensitive to many factors in engineering. When the scale factor fluctuates during the measurement process, it will bring an error to the angle measurement results if the scale factor is not calibrated in time. A scale factor real-time calibration and angle measurement scheme based on self-collimator is proposed to eliminate the error caused by the fluctuation of the scale factor. The experimental results show that the error between the FOG and the rotary table is decreased to nearly 1″ after adopting the scheme at low angular velocities. Although the error is become larger when the angular velocity is increasing, the angle measurement results can still has a good stability. [ABSTRACT FROM AUTHOR]

A new development in the dynamic angle measurement based on fiber optic gyro is described, in which a tilt sensor using for accurate measurement of the inclination angle is added to the dynamic goniometer, aiming to eliminating the misalignment angle and improving precision. The principle of the method to eliminate the misalignment angle is introduced in detail. A series of experiments have been carried out to verify this method. Experimental results show the measurement error of the goniometer is better than 2″ and the standard deviation is nearly 0.2″ by this method. It indicates that the method is effective for reducing the misalignment angle and improving the precision of the dynamic goniometer. [ABSTRACT FROM AUTHOR]

The multifunction integrated optical chip (MIOC) is one of the most critical parts of the interferometric fiber optic gyroscope (IFOG), and research on the halfwave voltage of the MIOC is meaningful for a high-precision IFOG. In this paper, the correlation between the frequency and halfwave voltage, which affects the interference light intensity of IFOG, is presented theoretically. A widespread measurement method for frequency dependence of the halfwave voltage, based on lock-in amplification and sinusoidal modulation, is proposed. Further, the measurement result and the oscillation of interference light intensity in the Sagnac interferometer are presented, which are in great agreement with the theory. This paper proposes the frequency dependence of the halfwave voltage and provides a new error research direction for the improvement of the MIOC in a high-precision IFOG. [ABSTRACT FROM AUTHOR]

We have analyzed the characteristics of 1.3 μm praseodymium (Pr3+) doped bidirectionally pumped double pass (BIP-DP) configuration amplified spontaneous emission (ASE) source theoretically and experimentally. The source's simulation model was established and corresponding simulated results were given. The effects of pump ratio, Pr3+-doped fiber (PDF) length, total pump power and source's optical losses were researched. The output power of BIP-DP ASE source is mainly affected by the total pump power, PDF length and source's optical losses, while it has little relationship with the pump ratio. The BIP-DP ASE source operating at the symmetric bi-directional pump condition was constructed experimentally. The acquired output power of more than 5 mW has been obtained experimentally, which was with the quasi-gaussian output spectrum, and its 3 dB bandwidth is ~ 20 nm. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]