Resonator Fiber Optic Gyro Research Articles

Angular random walk limited by Rayleigh backscattering in resonator fiber optic gyros.

This paper is concerned with the angular random walk (ARW) limited by Rayleigh backscattering in the resonator fiber optic gyro (RFOG) with a light source of arbitrary temporal coherence. First, a model of Rayleigh backscattering noise in RFOGs is established to predict the fluctuation characteristics of backscattered intensity and interference intensity. Next, the formula for the ARW limited by Rayleigh backscattering is derived, and the requirement of carrier suppression level is calculated to make sure the ARW is limited by the detector's shot noise rather than Rayleigh scattering noise. Finally, the influences of the cavity length, the linewidth, and the finesse on the ARW limited by Rayleigh backscattering are investigated. The results predict that the influence of the cavity length L and the laser linewidth ΔυL on the ARW is dominantly related to the factor e-2πΔυLneL/c, and under the finesse 88, the best ARW is obtained when there is a relation L·ΔυL≈4×105 m·Hz.

Analysis of polarization noise in transmissive single-beam-splitter resonator optic gyro based on hollow-core photonic-crystal fiber.

We realize a transmissive single-beam-splitter resonator optic gyro based on a hollow-core photonic-crystal fiber (HCPCF), utilizing a micro-optical coupler formed by pairs of lenses and one filter, which is a new type of resonator fiber optic gyro based on the HCPCF (HC-RFOG). We build a mathematical model of the polarization noise based on the transfer function of this novel transmissive single-beam-splitter resonator. We construct a HC-RFOG and simulate and validate the effects of polarization noise on the gyro system. In addition, we apply an effective method to suppress the polarization noise and prove its efficacy through experiments. The bias stability of the gyro system is successfully improved from 25 °/h to 2 °/h, which indicates a remarkable advance of performance of HC-RFOG.

Hybrid fiber resonator employing LRSPP waveguide coupler for gyroscope

Polarization error and temperature noise are two main limits to the performance of resonant fiber optic gyroscope (RFOG). To overcome these limits, we demonstrated a hybrid resonator consisting of a polymer-based long-range surface plasmon polariton (LRSPP) waveguide coupler and a silica fiber. Single-polarization property of LRSPP waveguide and the offsetting of the opposite thermo-optical characteristics between the polymer-based LRSPP waveguide and the silica fiber can effectively inhibit both the polarization error and the temperature noise of RFOG. The measured resonance spectrum of the hybrid resonator shows the absence of polarization noise. The temperature dependence of wavelength shift (TDWS) of resonator dropped to about 2 pm/°C, or even to 0 pm/°C with optimal structure, which dramatically improves the temperature stability of gyroscope system. In addition, the hybrid resonator also shows tremendous application potential in rate-grade and tactical-grade gyroscopes.

Analysis of Shupe Effect of Fiber Optic Ring Resonator Based on Photonic Crystal Fiber

Resonator fiber optic gyroscope (RFOG) is a new kind of high precision inertial sensor based on Sagnac effect by using a shorter fiber. This paper analyzes the noise induced by Shupe effect, and the characteristics of fiber optic ring resonator (FORR) based on photonic crystal fiber are analyzed. The influence of temperature on polarization and noise induced by Shupe effect are mainly investigated, and simulation results show that FORR based on photonic crystal fiber exhibits better performance than that of conventional fiber, and simulation shows that the noise induced by Shupe effect in FORR based on photonic crystal fiber is 7 times lower than conventional fiber.

谐振型光纤陀螺的灵敏度分析

谐振型光纤陀螺的灵敏度分析

谐振式光纤陀螺克尔效应误差的抑制

谐振式光纤陀螺克尔效应误差的抑制

Optimization of the sinusoidal phase modulation technique in resonant fiber optic gyro

The sinusoidal wave phase modulation and demodulation have been widely used in the signal processing system of the resonant fiber optic gyro (RFOG). An appropriate selection of the modulation frequency is of great importance, for the frequency value directly affects the slope of the demodulation curve at the resonance point which carries the gyro output information. A large demodulation slope is pursued in a high-performance RFOG. In this paper, an analytical expression of the demodulation slope is for the first time deduced in both transmission-type and reflection-type fiber ring resonators without any approximation. The relationship between the slope value and the modulation frequency at the resonance point is accurately calculated. The calculated best modulation frequency maximizing the demodulation slope at the resonance point is different from previous widely used optimal frequency given by the Lorentzian approximation method. More importantly, both theoretical and experimental results indicate that the achieved maximal demodulation slope from the proposed analytical expression method is double of that obtaining from the Lorentzian approximation method.

Measurement of the reflection and loss of the hybrid air-core photonic-bandgap fiber ring resonator.

A fiber ring resonator is the key element in a resonant fiber optic gyroscope (RFOG). Both reflection and loss characteristics can severely decrease the accuracy of the RFOG. This paper first implements optical frequency domain reflectometry (OFDR) to measure the reflection and loss coefficients of the hybrid air-core photonic-bandgap fiber (PBF) ring resonator. Compared with the traditional measurement method of the resonant curve, OFDR can clearly distinguish the two junctions between the air-core PBF and the solid-core fiber. The measured reflection coefficients at the two splicing points are 1.77% and 2.65%, respectively. The excess losses are 2.28dB and 3.22dB, respectively. Thus, the measurement of the junctions in the fiber ring resonator is realized.

Design of single-polarization coupler based on dual-core photonic band-gap fiber implied in resonant fiber optic gyro

A novel (to our knowledge) type of single-polarization (SP) coupler based on a dual-core photonic band-gap fiber (PBF) is proposed. The effects of structure parameters on the performance of this coupler are studied numerically based on the full vector finite element method (FEM). Finally, an optimal design with a length of 0.377mm at the wavelength of 1.55µm is achieved, and its implication in PBF-based fiber ring resonator (FRR), the effect of angular misalignment on the SP coupler are analyzed as well. When the SP coupler is incorporated into a PBF-based FRR, it functions as the power splitter and the polarizer simultaneously, and can extinct the secondary eigenstate of polarization (ESOP) propagating in the FRR. The mode field of SP coupler can match with the polarization-maintaining (PM) PBF with ultra-low temperature sensitivity proposed in previous study, and an all PM-PBF based FRR can be established, which is of great significance in suppressing the temperature-related polarization fluctuation and improving the long-term stability for RFOG, and the SP coupler has high angular misalignment tolerance as well.

An open-loop RFOG based on harmonic division technique to suppress LD's intensity modulation noise

A harmonic division technique is proposed for an open-loop resonator fiber optic gyro (RFOG) to suppress semiconductor laser diode's (LD's) intensity modulation noise. The theoretical study indicates the RFOG with this technique is immune to the intensity noise. The simulation and experimental results show this technique would lead to a diminished linear region, which still could be acceptable for an RFOG applied to low rotation rate detection. The tests for the gyro output signal are carried out with/without noise suppressing methods, including the harmonic division technique and previously proposed signal compensation technique. With the harmonic division technique at the rotation rate of 10deg/s, the stability of gyro output signal is improved from 1.07deg/s to 0.0361deg/s, whose noise suppressing ratio is more than 3 times as that of the signal compensation technique. And especially, a 3.12deg/s signal jump is significantly removed with the harmonic division technique; in contrast, a residual 0.36deg/s signal jump still exists with the signal compensation technique. It is concluded the harmonic division technique does work in intensity noise suppressing under dynamic condition, and it is superior to the signal compensation technique.

Resonant fiber optic gyro based on a sinusoidal wave modulation and square wave demodulation technique.

New developments are made in the resonant fiber optic gyro (RFOG), which is an optical sensor for the measurement of rotation rate. The digital signal processing system based on the phase modulation technique is capable of detecting the weak frequency difference induced by the Sagnac effect and suppressing the reciprocal noise in the circuit, which determines the detection sensitivity of the RFOG. A new technique based on the sinusoidal wave modulation and square wave demodulation is implemented, and the demodulation curve of the system is simulated and measured. Compared with the past technique using sinusoidal modulation and demodulation, it increases the slope of the demodulation curve by a factor of 1.56, improves the spectrum efficiency of the modulated signal, and reduces the occupancy of the field-programmable gate array resource. On the basis of this new phase modulation technique, the loop is successfully locked and achieves a short-term bias stability of 1.08°/h, which is improved by a factor of 1.47.

Parameter optimization analysis to minimize the polarization error in a localized thermal tunable fiber ring resonator gyro.

The accuracy of the resonant frequency servo loop is a major concern for the high-performance operation of a resonant fiber optic gyro. For instance, a bias error as large as tens or even hundreds of degrees/hour has been observed at the demodulated output of the resonant frequency servo loop. The traditional frequency servo mechanism is not an efficient tool to address this problem. In our previous work, we proposed a novel method to minimize the laser frequency noise to the level of the shot noise by refractive index modulation by a thermally tunable resonator. In this paper, we performed the parameter optimization for the resonator coil, multifunction integrated-optics chip, and couplers by the transition matrix using the Jones matrix methodology to minimize the polarization error. With the optimized parameter values, we achieved the bias value of the resonator fiber optic gyro to 1.924°/h.

光纤环形谐振腔输入功率波动对谐振式光纤陀螺的影响

光纤环形谐振腔输入功率波动对谐振式光纤陀螺的影响

光纤环形谐振腔输入功率波动对谐振式光纤陀螺的影响

光纤环形谐振腔输入功率波动对谐振式光纤陀螺的影响

Temperature dependence of beat-length and confinement loss in an air-core photonic band-gap fiber

The temperature dependence of polarization-maintaining (PM) property and loss in a highly-birefringent air-core photonic band-gap fiber (PBF) is investigated. The effects of temperature variation on the effective index, beat-length and confinement loss are studied numerically by using the full-vector finite element method (FEM). It is found that, the PM property of this PBF is insensitive to the temperature, and the temperature-dependent beat-length coefficient can be as low as 2.86×10−8m/°C, which is typically 200 times less than those of conventional panda fibers, the PBF has a stable confinement loss of 0.01dB/m over the temperature range of −30 to 20°C for the slow axis at the wavelength of 1.55μm. The PBF with ultra-low temperature-dependent PM property and low loss can reduce the thermally induced polarization instability apparently in interferometric applications such as resonant fiber optic gyroscope (RFOG), optical fiber sensors, and so on.

Comparative analysis of fiber ring resonator based on different fibers

Abstract A fiber ring resonator (FRR) is the core element in a resonant fiber optic gyro (RFOG) and its resonant depth, finesse and sensitivity determine the performance of RFOG. A configuration of FRR based on air-core photonic bandgap fiber (PBF), photonic crystal fiber (PCF) and panda polarization-maintaining fiber (PMF) is proposed, and the resonant depth, finesse and sensitivity of the FRR are comparative analyzed fully and in depth. It's found that: the FRR using PCF and PBF have better resonant depth than that of using PMF; the FRR using PCF has nearly the same performance as that using PMF, and may be a trade-off used in FRR before the existence of better PBF; the key factor that whether the FRR resonates in optimal resonant state is whether αc and kc of directional coupler satisfy the optimal resonant condition. These theoretical results are helpful to further study and optimize the RFOG based on different fibers.

A miniaturized compact open-loop RFOG with demodulation signal compensation technique to suppress intensity modulation noise

A miniaturized compact open-loop resonator fiber optic gyro (RFOG) prototype with main body size of about 10.4cm×10.4cm×5.2cm is reported, and a demodulation signal compensation technique is proposed, aiming to suppress the drift arising from accompanying intensity modulation induced by semiconductor laser diode (LD). The scheme of how to establish this miniaturized RFOG prototype is specifically stated. The linear relationship between the first-harmonic and second-harmonic demodulated signals respectively for the two counter propagating beams in the resonator is verified by theory and experiment, and based on this relationship, the demodulation signal compensation technique by monitoring the second-harmonic demodulated signal is described in detail. With this compensation technique, the gyro output stability under 1°/s rotation rate is effectively improved from 0.12°/s to 0.03°/s, and especially, an about 0.36°/s peak-to-peak fluctuation due to tuning current reset is significantly suppressed. A long term bias stability of about 4.5°/h in 1h for such a small-sized RFOG prototype is demonstrated, which is of the same magnitude as that of currently reported large-sized RFOG systems utilizing LD as the laser source as well.

Laser frequency noise induced error in resonant fiber optic gyro due to an intermodulation effect.

For the first time, a significant noise source in the resonant fiber optic gyroscope (RFOG) called intermodulation induced error is proposed and deeply analyzed in this paper. The intermodulation error is produced by the laser frequency noise at even multiples of the modulation frequency due to an intermodulation effect, which will seriously limit the random noise performance of the RFOG. Experiments are designed and conducted to verify and measure the intermodulation induced error in the RFOG. The experimental results confirm the existence of intermodulation error, and fit well with the theory. As for the design of the RFOG, light sources with a narrow intrinsic linewidth and a high modulation frequency are preferable to achieve a high rotation-rate sensitivity.

Systematically analysis of resonant fiber optic gyroscope

The research on gyroscopes has lasted for a long time, but there is not a thorough analysis of them. In this paper, a detailed theoretical analysis of fiber ring gyroscope and its gyroscope effect are presented, the performance characteristics of optical resonator gyroscope ranging from transmission function Tfrr, Finesse, Q-factor, the gyro sensitivity, signal noise ratio, random walk to dynamic range are all deduced in detail. In addition, a large number of experiments have been done to verify the deduced theoretical results. The sensitivity of the fiber optic gyroscope is analyzed by simulating the relationship between dQ and turn number of fiber ring, make the conclusion that with the increase of turn number of ring, the resonance depth increased while the dQ value decreased, obtain a high sensitivity of 0.21°/h, random walk of 0.0035°/√h, and Q factor of 8×106. Moreover, in the digital frequency locked dual rotation gyro experiments, obvious step effect is observed. And the experimental line of frequency difference is very agreement with the theoretical line. The research provides a good theoretical and experimental basis for the study of gyroscopes.

Analysis of temperature effect in fiber optics ring resonator based on photonic crystal fiber

Aiming at the requirements of high accuracy, miniaturization and high stability in resonator fiber optic gyroscope (RFOG), photonic crystal fiber (PCF) is used in the fiber optic ring resonator (FORR). Effective refractive, birefringence and nonlinear coefficient sensitivity to temperature of PCF are analyzed by using finite element method (FEM), and results show that the magnitude of effective refractive, birefringence and nonlinear coefficient are 10−7, 10−10 and 10−9, respectively, which exhibit better performance than that of conventional fiber. This will reduce the errors induced by temperature fluctuation. The polarization fluctuation to temperature of fiber optic ring resonator (FORR) based on PCF is also analyzed, and results show that PCF is a valuable alternative, which will be helpful in improving the stability and accuracy of RFOG.