Electrical crosstalk-coupling measurement and analysis for digital closed loop fibre optic gyro

The phase modulation and the closed-loop controller can generate electrical crosstalk-coupling in digital closed-loop fibre optic gyro. Four electrical cross-coupling paths are verified by the open-loop testing approach. It is found the variation of ramp amplitude will lead to the alternation of gyro bias. The amplitude and the phase parameters of the electrical crosstalk signal are measured by lock-in amplifier, and the variation of gyro bias is confirmed to be caused by the alternation of phase according to the amplitude of the ramp. A digital closed-loop fibre optic gyro electrical crosstalk-coupling model is built by approximating the electrical cross-coupling paths as a proportion and integration segment. The results of simulation and experiment show that the modulation signal electrical crosstalk-coupling can cause the dead zone of the gyro when a small angular velocity is inputted, and it could also lead to a periodic vibration of the bias error of the gyro when a large angular velocity is inputted.     

基于对称性评估的保偏光纤偏振轴检测技术

提出一种基于端面图像对称性特征的偏振轴检测算法。该算法利用图像极坐标变换来实现图像的对称性检测,使用金字塔搜索法快速寻找最优对称轴,确定偏振轴向。所提算法利用图像的全局性特征而不依赖于应力区边缘点位置实现精确定位,对图像清晰度要求显著降低。实验结果表明,所提算法具有较高的准确性和精确性(±0.1°),其稳健性大幅增强,且算法速度提升了近1.5倍。     

Radiation-induced effects in polarization-maintaining optical fibers for interferometric gyroscope

Radiation-induced attenuation (RIA) in four types of polarization-maintaining optical fibers for interfer-ometric fiberoptic gyroscope (IFOG) at 1310 nm is measured. The measurements are conducted during and after steady-state γ-ray irradiation using a 60 Co source in order to observe significantly different RIA behavior and recovery kinetics. Mechanisms involving dopants and manufacturing process are introduced to analyze the RIA discrepancy as well as to guide the choice and hardening of optical fibers during the design of IFOG. Medium-accuracy IFOG using Ge–F-codoped fiber and pure silica core fiber can survive in the space radiation environment.     

Gamma-radiation effects in pure-silica-core photonic crystal fiber

We investigated the steady state gamma-ray radiation response of pure-silica-core photonic crystal fibers(PSC-PCFs)under an accumulated dose of 500 Gy and a dose rate of 2.38 Gy/min. The radiation-induced attenuation(RIA) spectra in the near-infrared region from 800 nm to 1700 nm were obtained. We find that the RIA at 1550 nm is related with hydroxyl(OH-) absorption defects in addition to the identified self-trapped hole(STH) defects. Moreover, it is proposed and demonstrated that reduced OH-absorption defects can decrease the RIA at 1550 nm. The RIA at 1550 nm has effectively declined from 27.7 d B/km to 3.0 dB/km through fabrication improvement. Preliminary explanations based on the unique fabrication processes were given to interpret the RIA characteristics of PSC-PCFs. The results show that the PSC-PCFs,which offer great advantages over conventional fibers, are promising and applicable to fiber sensors in harsh environments.