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A coupling effect in the single-mode fiber coil (SMFC) of a depolarized interference fiber optic gyroscope (De-IFOG) under time-varying temperature and magnetic field, which can cause a serious nonreciprocal phase error, is revealed. In this paper, the mechanism of the coupling effect is thoroughly studied and the related theory is derived in detail. Simulations and experiments are carried out to verify the validity. The experiments show a peak-to-peak value error of about 50 °/h in the SMFC when the magnitude of magnetic field is 10 Gauss and the temperature uniformly increases from 10 to 60 °C at the rate of 36 °C/h, which cannot be neglected in the applications of De-IFOGs. [ABSTRACT FROM AUTHOR]

This paper aims to investigate the nonreciprocity caused by orthogonal magnetic field (OMF) vertical to the light direction propagating in a polarization-maintaining fiber-optic gyro (PM-FOG). In orthogonal magnetic field, the nonreciprocal phase error (NPE) results from the small change of the propagation constants of the two opposite light waves propagating in the fiber coil. Even using a PM fiber coil, the pressure, twist, and other imperfections will change the polarization state, which may lead to an instable drift in PM-FOGs. This phenomenon was observed in the 0°-coupling regime which is commonly used for PM-FOG systems. Theoretical analysis and experimental results show and confirm that the instability of the NPE can be evidently reduced by taking a double-45°-coupling scheme. In this case, the NPE appears to be linear to the OMF and can therefore be compensated via later processes. [ABSTRACT FROM PUBLISHER]

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]

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]

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]

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]

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]

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]