Dynamic response of a fiber-optic ring resonator: Analysis with influences of light-source parameters

In practice, dynamic behavior of fiber-optic ring resonator (FORR) appears as a detrimental factor to influence the transmission response of the FORR. This paper presents dynamic response analysis of the FORR by considering phase modulation of the FORR loop and sinewave modulation of input signal applied to the FORR from a laser diode. The analysis investigates the influences of modulation frequency and amplitude modulation index of laser diode, loop delay time of the FORR, phase angle between FM and AM response of laser diode, and laser diode line-width on dynamic response of the FORR. The analysis shows that the transient response of the FORR strongly depends on the product of modulation frequency and loop delay time, coupling and transmission coefficients of the FORR. The analyses presented here may have applications in optical systems employing an FORR with a laser diode source.     

Observation of coherence effects in a quasi-monochromatic fiber-optic gyroscope

The sensitivity reduction resulting from a loss of fringe visibility due to the limited coherence of the broad-band source in a fiber-optic gyroscope is observed. The experimental data is well described by coherence theory assuming a Gaussian spectral shape for the superluminescent diode source.     

无源谐振腔激光陀螺实验系统的研制

报道了采用反射型谐振腔结构的无源谐振腔激光陀螺系统。在实验室环境下,取得了漂移稳定性1.7deg/h的性能。指出了引起陀螺漂移的误差因素,并提出进一步改善陀螺测量精度的措施。     

光子晶体光纤陀螺标度因数特性研究

光子晶体光纤陀螺原理上具有磁敏感性低、温度稳定性好及抗辐照等特点,是光纤陀螺一个新的重要发展方向。很多学者研究了其零偏特性,但未见对其标度因数的研究报道。研究了光子晶体光纤陀螺标度因数的误差构成,并试验测量了光子晶体光纤环引入的误差。研究结果表明,光子晶体光纤陀螺标度因数具有更稳定的温度和辐照特性,在-40~+70℃的温度范围内,标度因数重复性为242.310-6(未补偿时),约为普通光纤陀螺的1/2。在经历总剂量为50 krad(Si)的辐照后,光纤陀螺标度因数变化10910-6,重复性和非线性没有明显变化,比普通光纤陀螺稳定1 倍以上。     

多线程的光陀螺信号采集系统设计

为满足导弹对光陀螺信号实时性的要求,设计并实现了光纤陀螺的信号实时采集,并进行实时数据的动态显示与处理。采用C Builder5.0平台来设计光纤陀螺信号采集部分。陀螺信号的采集通过计算机的串口传输。该光纤陀螺的输出为RS232格式,通过调用Windows API函数实现RS232串口通信程序,并采用了多线程的技术来增强实时性和自动接收信号的能力。通讯速率38.4 kB,通讯期间可以完成数据处理,并且基本没有丢数现象;完成了数据包的解算;实现了线程间的数据共享与数据的实时处理。基于C Builder5.0和Windows系统的多线程串行通信可以实现实时数据的采集,同时可以在另一个线程中进行数据的实时处理。数据接收稳定可靠,取得了良好的效果。     

光纤环形谐振腔输入功率波动对谐振式光纤陀螺的影响

谐振式光纤陀螺是一种基于Sagnac效应的高精度惯性传感器。作为一种互异性噪声,光纤谐振腔输入功率的波动会造成陀螺的检测误差。首先,分析了光纤谐振腔输入功率波动产生噪声的机理。通过对不同输入功率下的谐振腔传输特性和陀螺解调输出的理论及实验分析得到了谐振腔输入功率波动引起的检测误差的表达式。当输入角速度为500（）/s、输入功率为0.69 mW时,0.007 5 mW的功率波动会引起5.26（）/s的检测误差。其次,研究了谐振腔输入功率波动对陀螺标度因数的影响。通过计算发现随着输入功率波动的增大,解调曲线的线性区将会发生扭曲,同时陀螺的标度因数非线性度会恶化,为谐振式光纤陀螺中输入功率波动噪声的估测提供了参考。     

Observation of low noise in a passive fibre gyroscope

We report short-term noise levels of < 1 deg/h and 10 min drift of < 2 deg/h in a passive fibre gyroscope utilising a fused 3 × 3 fibre coupler and a broadband and partially polarised superluminescent diode. Partially polarised operation of the source is shown to result in less noise than polarised operation.     

微光学陀螺楔形谐振腔制备技术研究

Si基谐振式光学微腔陀螺以小型化、集成化成为未来姿态检测领域的发展趋势,其极限灵敏度主要取决于谐振腔直径D与品质因数Q值乘积,目前常见的硅基微腔直径为微米级,为了进一步提高极限灵敏度,实验中控制加工工艺减小反应过程中残余应力与表面粗糙度,制备出直径D为8mm、表面粗糙度小于1nm、Q值2.4×106的大尺寸硅基SiO2楔形谐振腔,可实现陀螺极限灵敏度达到55°/h,为芯片级、集成化的新型谐振式光学微腔陀螺的研究奠定了实验基础。     

干涉式光纤陀螺中Shupe效应与Sagnac效应的分离

热引入的零偏漂移即Shupe效应是提高光纤陀螺精度面临的最大难题。基于Shupe效应与光纤陀螺的Sagnac效应具有本质的不同特性,即Sagnac效应引起的相移只与几何尺寸有关,而与光传播的介质特性无关,提出了一种新型的不受温度梯度影响的光纤陀螺。利用两个偏振模式在光纤陀螺环中交替或同时传播可以将Sagnac相移与Shupe误差相移分离开来,基于两种偏振模式分时传播实验,初步验证了该理论的可行性。并且提出了一种新型的偏振交替干涉式光纤陀螺模型以改进其性能。     

光源光谱对光纤陀螺偏振误差的影响

以采用Y波导集成光学调制器的保偏型干涉式光纤陀螺(IFOG)为研究对象,根据各光学元器件的参数,建立了各器件的琼斯矩阵以及光路传输模型,通过推导得到了保偏型IFOG的偏振误差表达式。在此基础上,首次借助宽谱光源的光谱,仿真计算了不同形状的光源光谱对偏振模式耦合误差的影响。通过计算得出,当光路中其他参数不变时,对于形状相似的光谱,在光纤陀螺中带来的偏振误差相差约10-5 (°)/h;而形状相差较大的光谱带来的误差值相差较大,约10-2 (°)/h;在谱宽相差不大的情况下,光谱的平均波长在长波长处、近高斯形状的光源在陀螺系统中产生的偏振误差比平坦光谱小。这一结论对IFOG的光源选择有一定的指导意义。     

Demodulation of interferometric sensors using a fiber-optic passive quadrature demodulator

The passive quadrature demodulator (PQD) eliminates the phase stretcher and feedback electronics frequently used in fiber interferometric sensors by passively extracting the desired signal using two distinct interferometers which differ in phase bypi/2. A fusion technique is described to fabricate a fiber PQD which is sufficiently stable with respect to temperature, polarization, and wavelength to maintain the sensitivity of interferometric sensors constant to 0.25 dB.     

A novel fiber-optic Fabry-Perot resonator with two mode-conversionmirrors: proposal and application

A novel fiber-optic Fabry-Perot resonator composed of a piece of fiber with two LP₀₁&rlarr2;LP₀₂ mode-conversion reflectors is proposed and theoretically investigated. The reflective fiber-optic LP₀₁&rlarr2;LP₀₂ mode converter is analyzed based on the coupled-mode theory. The resonance characteristics including the transmission, reflection, and circulation of this novel fiber resonator are examined. In addition, we also describe the application of this device as an optical filter which can be used for FDM/WDM communications, etc. In contrast to a conventional Fabry-Perot optical filter with a periodic output spectrum, our proposed optical filter has only one peak in output spectrum, while the bandwidth of the filter spectrum is very narrow, with several Megahertz determined mainly by the cavity length of the fiber resonator. Finally, it is demonstrated that the characteristic of this optical frequency filter can be greatly improved by introducing a gain mechanism using a rare-earth-doped fiber. The tunable performances of this optical filter are also presented     

Analysis of optical phase noise in fiber-optic systems employing a laser source with arbitrary coherence time

Performance of many optical circuits and systems, such as signal processing and sensing devices, is influenced by random fluctuations of the optical source emission field. This paper outlines a formalism for the analysis of laser phase noise effects on a general linear time-invariant optical system. Theoretical expressions are presented for the autocovariance function of the instantaneous output intensity which are valid for any source coherence time as long as the source intensity fluctuations are assumed to be negligible. Applications of the results to some fiber-optic systems such as Mach-Zehnder and recirculating delay line devices also are demonstrated, both in the coherent and incoherent regimes. Although the analysis is not limited just to fiber-optical systems, our attention is focused on fiber optics.     

光纤陀螺系统中信号光反馈下的激光光源强度噪声特性研究

从建立光纤陀螺激光光源受信号光反馈作用时的等效腔模型出发,对影响光源强度噪声的诸因素进行了理论分析,结果与实验很好符合,并提出了消除信号光反馈对系统性能影响的方法.     

高精度光纤陀螺用掺铒光纤光源辐照性能试验

针对高精度光纤陀螺的空间应用,理论分析了用于高精度光纤陀螺的不同结构掺铒光纤光源的抗辐照性能,指出了单通后向结构的掺铒光纤光源具有更好的抗辐照性能。对单通后向结构采用不同掺杂浓度的掺铒光纤设计并研制了掺铒光纤光源,在实验室用Co60辐照源进行了大小两个剂量率的辐照试验,监测了掺铒光纤光源平均波长和输出光功率随辐照总剂量的变化,试验结果表明:掺铒光纤掺杂浓度较高时,掺铒光纤光源的抗辐照能力较强;辐照剂量率较小时,掺铒光纤光源功率随辐照总剂量的降低速度更慢。掺杂浓度较高的掺铒光纤光源可以满足高精度光纤陀螺空间应用的要求。     

Dependence of modal noise on source coherence and fibre length

A transmission model for optical communication systems with partially coherent sources has been developed and the dependence of modal noise and distortion on (a) the fibre length between source and connector, and (b) the lateral offset at the connector was investigated.     

The vibration error of the fiber-optic gyroscope rotation rate and methods of its suppression

The error of the fiber-optic gyroscope (FOG) rotation rate measurement is considered. This error is induced by FOG vibrations (for open- and closed-loop FOGs). For a closed-loop FOG, a differential equation describing the loop dynamics is derived. The coefficients of this equation contain terms varying in time with the vibration frequency. For the first time, it is shown that, in addition to the traditional rotation rate measurement error due to the superimposition of vibration-induced optical power oscillations and the phase difference in the FOG coil, there is one more error, which is due to vibration modulation of the loop bandwidth. Alternative methods of information processing are investigated, and, on the basis of them, a new circuit is proposed for the suppression of vibration errors.     

Coupling parameters for a side-coupled ring resonator and amicrostrip line

A ring resonator side coupled to a microstrip line shows two close but distinct resonance peaks. These are identified as due to even-mode (magnetic field) and odd-mode (electric field) coupling. Equivalent circuit models for both cases have been proposed and coupling parameters are calculated using piecewise, coupled-line approximations. The calculated coupling coefficients for the two cases are compared with the experimentally-measured coupling coefficients and show very good agreement with the models used     

Influence of a low-Q shunting medium on the equivalent parameters of a cavity resonator

The influence of the dielectric loss of a low-Q shunting medium on the parameters of the equivalent circuit of a cavity resonator is analyzed. The effect is studied for a radial cavity resonator partially filled with a lossy medium. The influence of field absorption by the shunting medium on the frequency and Q factor of the oscillation excited in the cavity and, consequently, on the parameters of the equivalent oscillatory circuit is studied by means of electrodynamic modeling. It has been found that the loss level changes not only the Q factor but the characteristic impedance of the equivalent circuit.     

反射镜热形变对激光器谐振腔参数的影响

本文讨论了反射镜热形变对激光谐振腔参数的影响.在具体设计高功率激光器,特别是折迭式CO_2激光器谐振腔时,应尽可能预先考虑这种影响.