实用中低精度光纤陀螺的信号处理设计

开环光纤陀螺系统直接从探测器的电信号解算出光纤陀螺的Sagnac相移，具有结构简单、全光纤、成本低廉等优点。所以开环光纤陀螺是满足中低精度应用要求的比较理想的方式。为了在开环光纤陀螺结构中满足大动态范围和高测量精度的要求，系统的信号处理方案利用多次谐波分析的数据处理方法，并且结合高阶契比雪夫FIR滤波器、自适应最佳采样速度设定、频谱分析技术、数字相关处理等数字信号处理技术，实现了2deg/h的精度。本文除了介绍上述设计方法外，并且通过对实验结果的对比测试分析，提出进一步提高光纤陀螺精度和稳定度的途径和设想。     

Novel fibre optic gyroscope with a configuration combining Sagnac interferometer with fibre ring resonator

A novel fibre optic gyroscope, with a structure making use of the combination of a Sagnac interferometer with an active fibre ring-resonator, is proposed and analysed. The proposed gyroscope can be viewed as a generalised structure of the conventional Sagnac interferometric type fibre optical gyroscope. It has the advantages of both long fibre loop length and multipath interferences. By inserting a fibre amplifier in the loop to provide an optical gain of several dB, the relative maximum sensitivity is enhanced to approximately 30 times more than that of conventional Sagnac interferometric fibre optic gyroscopes.<>     

Optical phase-locked loop with fibre lasers for low phase noise millimetre-wave signal generation

An optical phase-locked loop (OPLL) using two continuous-wave commercial fibre lasers was implemented by means of pump power modulation. Although the 3 dB bandwidth of the frequency modulation transfer function of a fibre laser was measured to be approximately 6 kHz, the control bandwidth of the loop was extended by a factor of 10 using electronic phase-lead compensation. The operation of our OPLL was stable with a residual RMS phase fluctuation of 57 mrad. By using this technique, the photonic generation of millimetre-wave signals up to 64 GHz was successfully demonstrated.     

A digital signal processing type frequency locked loop for frequency shift keying demodulation

In this paper, we propose a digital signal processing type frequency locked loop (DSP-FLL) using a frequency difference detector (FDD). Since the DSP-FLL is controlled by the frequency, the pole of the voltage controlled oscillator vanishes in the baseband equivalent circuit. Therefore, the transfer function becomes first order and a ringing does not occur. Furthermore, it can be understood from the detection property of the FDD that a cycle slip does not occur and the DSP-FLL can pull in the frequency step input up to half of the sampling frequency.     

光纤陀螺全频域小波阈值降噪技术

为了有效地去除光纤陀螺信号中的分形噪声,提出了全频域小波多尺度阈值降噪方法。从分形信号的分数微分形式出发,建立了分形信号与高斯白噪声之间的联系,结合小波分析的高阶消失矩特性,实现了分形信号在小波空间的去相关。当分形信号被具有高阶消失矩的小波分解后,其在小波域具有白噪声的特点,可以采用阈值处理的方法予以去除。同时,根据陀螺信号噪声的宽频带特点,对小波分解的低频近似系数和高频细节系数进行阈值处理,有效地抑制了噪声成分。光纤陀螺信号的降噪实例表明:相比传统的小波阈值降噪方法、卡尔曼滤波方法和滑动平均滤波方法,该方法具有较好的降噪效果。     

Two-wavelength fibre gyroscope with wide dynamic range

An optical fibre gyroscope configuration which utilises dual-wavelength determination of the Sagnac shift is described. It is shown that this provides a means of extending the unambiguous rotation sensing range, and thus the dynamic range, of the gyroscope. Using an all-fibre system and sources at wavelengths of 812 nm and 842 nm, an increase in unambiguous sensing range of approximately 27 times is demonstrated.     

Microstructure fibre array for RF photonic signal processing applications

A novel microstructure fibre array (MFA), comprising multiple singlemode fibre waveguides reduced to an overall diameter of approximately 30 /spl mu/m is reported. When used in conjunction with a single photodetector, the array facilitates the efficient and stable electrical summation of a number of RF-modulated optical signals with minimal optical interference effects. The reported MFA has optical insertion loss less than 0.1 dB. An RF filter based on the array exhibits less than 0.4 dB optical insertion loss and excellent temporal stability.     

采用双Y型LiNbO_3集成光路的闭环光纤陀螺研究

集成化已成为研制中、高精度大动态范围光纤陀螺的一个必然途径。文中报道了一种采用光纤滤波/双Y型集成光路和全数字处理的闭环光纤陀螺,其中光纤滤波/双Y型多功能集成光路是采用退火质子交换法(APE)在铌酸锂衬底上制作而成的,它包含了光纤陀螺所需的除光纤线圈以外的无源光学器件的全部功能:两个分光/合光器(耦合器)、两个宽带相位调制器(推挽工作)和一个高消光比的偏振器,测试结果表明,陀螺零偏稳定性优于1°/h。该陀螺结构紧凑、动态范围大、精度适中、成本低,特别适合于战术级的应用     

Novel passive phase noise cancelling technique for interferometric fibre optic sensors

A novel technique for the cancellation of phase noise in a fibre interferometer caused by laser frequency emission jitter is described. The scheme is based on the use of a reference interferometer and phase generated carrier passive homodyne phase detection. Signal processing involving cross-multiplication of the sine and cosine components of the sensor and reference interferometer outputs is shown to provide cancellation of phase noise.<>     

一种针对压缩域信号的新型锁相环技术

针对通信信号压缩采样获得的压缩域信号频率、相位提取问题,提出了一种基于压缩感知的新型锁相环技术。通过深入研究压缩域的信号估计问题,提出了压缩域锁相环路,可以直接在压缩域同步跟踪信号频率和相位变化,不再需要高复杂度的信号重构处理。分析了环路模型及其估计性能,并针对该锁相环可行性和性能分别进行了仿真实验。仿真结果不仅验证了压缩域锁相环的可行性,同时表明该环路能够实现高动态信号的高精度频率提取。压缩域锁相环的应用潜力较大,例如可以作为压缩感知通信接收机的同步解调方法。     

Reduced phase error of a fiber optic gyroscope using a polarization maintaining photonic crystal fiber

We report the first measurement of the polarization crosscoupling of a 900-m length of quadrupolar-wound sensing coil for the fiber optic gyroscope (FOG) using polarization maintaining photonic crystal fibers (PM-PCFs). The crosscoupling is analyzed with the Optical Coherence Domain Polarimeter (OCDP). Also the polarization extinction ratio (PER) of the PM-PCF coil is measured. For comparison, a standard panda fiber coil with nearly the same length is examined. The results show that PER of the PM-PCF coil is ～10 dB larger than the panda fiber coil, and polarization crosscoupling in the PM-PCF coil is ～10 dB less than in the panda fiber coil. Moreover, based on measurements, a 4-fold reduction in phase error is demonstrated numerically in a FOG made of the PM-PCF coil, compared to the same gyro operated with a similar coil of panda fiber. These findings have important benefits in a higher measurement precision and stability of FOG.     

一种处理信号相位误差电路的设计

介绍了一种对两种不同相位关系的正弦信号进行相位后比较所产生的直流电压信号进行一定处理,然后用处理过的信号对系统进行控制,将其相位做已校正,文中把电路工作过程、外形设计和加工具体过程做了较仔细的叙述,该系统可工作在较宽的环境范围。同时可以满足于多个领域的使用要求。     

用于光学相位检测的数字信号处理系统

介绍了一种利用数字信号处理技术和虚拟仪器技术实现对微弱光学相位信号进行高精度频率、幅度测量的方法。该方法实现了反馈式数据采样率的设定、自适应数字带通带阻滤波器和全数字相敏检波等功能,并且可以对信号相位和强度以及谐波进行精确测量     

基于信号处理的选相分合闸技术

基于传统的交流电器选相分合闸技术,考虑其中存在的采样速率慢及合闸控制实现方式等问题,提出了一种新的基于单片机的解决方案。从提高相位计算精度出发,采用高速采样的高性能单片机进行数据采集;在合闸环节,以电压零相位取代瞬时相位作延时参考,避免了在瞬时相位计算过程中由频率波动引起的误差;在功率因数角的计算上,采用FFT变换,由上位机进行数据处理以取代单片机的计算,解决了由单片机对大量采样数据进行FFT计算造成的严重耗时问题。该方案提高了信号相位测量的准确度,使得选相合闸更加准确。     

基于广义卡尔曼滤波的光学膜厚监控信号处理

为了解决光学膜厚监控系统中经锁相放大输出的监控信号精度较低、极值点附近变化不灵敏等问题,采用卡尔曼滤波(KF)对光学膜厚监控信号进行处理,建立了针对非线性光学监控系统的扩展KF模型,模型输出包括监控信号和导数信号。仿真分析首先利用TFCalc软件生成4层增透膜理想监控曲线,加入高斯噪声后,信噪比为15dB,通过卡尔曼滤波处理后监控信号信噪比改善达16dB且实时动态跟踪特性良好,延时小于1s;利用平均值滤波处理KF输出导数信号,提前预判读获取导数过零点对应膜厚。同时通过对比TFCalc理想监控曲线极值点坐标和预判导数信号过零点坐标,得到理论膜厚误差小于4nm。此项研究提高了膜厚检测的准确性。     

Explanation of polarisation dependence of differential phase shift in two-mode elliptic-core fibre strain gauges

An appropriate elliptic-core fibre theory is applied to model the differential phase shift between the first- and second-order modes observed in recent experiments on two-mode elliptic-core fibres subjected to longitudinal strains. The theory provides an explanation of the polarisation dependence of the stretching delta l/sub 2 pi / required to produce a 2 pi differential phase shift between the two modes as a function of wavelength for both polarisations.<>     

20 GHz all-optical clock recovery based on fibre laser mode-lockingwith fibre nonlinear loop mirror as variable intensity/phase modulator

All-optical clock recovery is demonstrated at 20 Gbit/s with a fibre-based nonlinear loop mirror used as an intracavity modulator in a mode-locked fibre laser. The effect of combining AM and FM modulation simultaneously is analysed theoretically and experimentally     

Magnetooptical waveguides with polarization-independentnonreciprocal phase shift

Magnetooptical waveguides having nonreciprocal phase shift for both TE and TM modes can be prepared by properly adjusting the spatial variation of the Faraday rotation. Such waveguides are attractive to realize optical isolators. We investigate four concepts of magnetooptical waveguides which yield equal nonreciprocal phase shifts for the fundamental TE and TM modes. A polarization-independent Mach-Zehnder-type integrated optical isolator is presented. All the calculations are performed using material parameters typical for garnet films     

基于双频锁定的谐振式微光陀螺背散噪声抑制

经过十余年的发展,谐振式微光陀螺(RMOG)系统中的光学噪声依旧是制约陀螺输出精度的重要因素,其中背向散射噪声是谐振式微光陀螺系统中的主要光学噪声之一。本文首先分析了背散噪声产生机理,建立了谐振式微光陀螺系统背散噪声数学模型。其次,利用不同频率激光,将CW与CCW光路中的背散噪声与反向光信号的相干噪声信号移频至高频段并滤除,实现背散噪声抑制的方法。并利用双激光器双频锁定的方法进行了验证。实验结果显示,谐振曲线中背散噪声被有效抑制,从而使谐振式微光陀螺系统锁频精度提高了5倍,锁频精度达到6 °/h。