谐振式集成光学陀螺噪声分析与实验研究

针对目前谐振式集成光学陀螺(IORG)输出检测精度与其理论极限灵敏度存在两个数量级差别的情况,分析了IORG系统中存在的主要噪声源;搭建了基于单光路锁频和单光路输出的IORG噪声分离系统;分别对无光情况下信号检测系统中各部分的噪声以及陀螺静态频率锁定情况下各部分的噪声影响进行了测试与分析;得到了系统的噪声分布情况。实验结果表明:光路噪声以及包括探测器热噪声和散粒噪声的电路固有噪声为系统的主要噪声源。     

Sensitivity limitation by polarization and birefraction in IORG

Integrated optical resonance gyroscope (IORG), with the ring resonator fabricated by micro-techniques, has the advantage of miniaturization, integration, and low cost. Theoretical calculation shows its potential ability in getting high sensitivity. However, the current IORG sensitivity is restricted by optical parasitical noises aggravated by involving high coherent laser source. Polarization fluctuation is one of the dominant noise sources in waveguide resonator. The effect on polarization noise in IORG by three main parameters: state of polarization of the input light, polarization-maintaining quality of the waveguide, and temperature fluctuation of the peripheral environment, has been theoretically analyzed and experimentally tested. An improved layout, with a Planar Lightwave Circuit (PLC) acting as both modulator and polarizer, is presented to suppress the polarization noise in IORG. The results show that the bias instability of IORG caused by polarization noise is greatly reduced from 1.57°/s to 0.005°/s.     

谐振式集成光学陀螺解调特性分析

基于激光器频率谱检测技术,沿着光的传输方向分析了光波在谐振式集成光学陀螺系统中的传播,结合输入信号特征,建立频域内的数学模型,通过数值仿真和实验得到了调频检测系统下的解调曲线。按照光的传输方向：激光器、声光晶体移频器、光波导环形谐振器、探测器,利用贝塞尔函数展开和光场耦合模理论分析了谐振式集成光学陀螺解调特性,及其调频调制检测系统解调输出信号与谐振频率偏差之间的关系。通过数值计算,分析了解调曲线的变化规律,得到了施加在激光器压电陶瓷驱动器上调制波形的最佳调制系数。在实验上搭建了激光器频率调制解调技术系统,得到了解调曲线。数值仿真和实验结果表明,当调制系数M=2时,线性工作区间斜率最大,解调曲线最好。实测形状与理论分析结果相符,从解调信号得到±2×10³ rad/s的陀螺动态范围。     

渐变折射率传感气室中干涉噪声的数值模拟与分析

在直接红外吸收式光纤气体传感器中,由渐变折射率（Graduated Refractive Index,GRIN）棒透镜构成的微型传感气室有着广泛的应用。分析了GRIN气室中的干涉噪声信号和甲烷信号,并利用MATLAB对干涉噪声信号的幅值与分布反馈式半导体激光器（DFBLD）的频率调制幅度之间的关系以及干涉噪声对气体检测灵敏度的影响进行了数值模拟与分析。当前谐波检测技术是气体检测的一种非常重要的技术,这种技术需要检测气体吸收信号的一次、二次或更高次谐波。而GRIN气室的二次干涉噪声对浓度信号有很大的影响,研究发现当频率调制幅度达到某些特定频率值时,二次干涉噪声信号的幅值变为零,通过调整气室参数和DFBLD的调制频率可以削减干涉噪声的影响从而提高谐波检测技术的检测灵敏度。     

SOI微环谐振腔测试信号纹波噪声的分析

基于绝缘体上硅材料（SOI）的微环谐振腔作为各种集成微光学器件的核心部件,其传输特性的好坏直接决定微光学器件的性能优劣。结合微环谐振腔理论和多光束干涉原理对微环谐振腔测试信号中纹波的产生原因和影响因素进行了分析,通过耦合实验测试得到了纹波信号的特征参数并进行了分析,实验结果与仿真分析吻合。进一步分析了耦合光栅刻蚀深度对纹波幅值的影响及原因,为微环谐振腔结构参数的进一步优化和微环谐振腔传感系统误差分析提供了依据。     

光纤环形谐振腔的频率锁定及其特性

基于可调分束比的光纤分束器,制作了光纤环形谐振腔并通过调节分束比实现了对光纤环形谐振腔的欠耦合、临界耦合和过耦合的状态控制.实验测量了腔最小反射率与腔损耗之间的关系,获得光纤环形谐振腔的腔内衰减率为κ_0=2π×(1.60±0.03) MHz ,品质因子为Q=(1.10±0.02)×10.8.在此基础上,结合了压电陶瓷拉伸光纤以控制腔长和Pound-Drever-Hall锁频两大技术优势,克服了之前温度反馈控制等方法的反馈带宽窄、噪声大和稳定性差等问题,实现了对光纤环形谐振腔共振频率的快速、灵敏的控制和锁定.结果表明,锁频过程中相位调制功率与相位调制引起腔反射光的强度调制之间的关系为线性关系,进而通过降低相位调制信号的功率以减小相位调制对腔反射光强度调制的影响.当调制功率设定最低为–9 dBm时,光纤环形谐振腔仍能被稳定锁定.该光纤环形谐振腔为其与原子、金刚石色心等发光粒子相互作用的腔量子电动力学实验研究奠定了坚实的基础.     

多波长双向抽运光纤拉曼放大器的优化设计

通过合理分析提出了便于计算多波长双向抽运光纤拉曼放大器信号及噪声功率的实用数值模型,给出求解信号和噪声功率的快速算法。在定义抽运方向度为前向抽运功率与总抽运功率值的比值后,通过对计算结果的分析发现信道平均放大自发辐射噪声功率随着抽运方向度的提高而单调递减;而信道平均双重瑞利散射噪声功率相对抽运方向度的变化曲线始终成U字形。不同的增益下存在对应的最优抽运方向度,在此抽运方向度下放大器总噪声最低。进而考虑在信号非线性失真的条件下提出了抽运方向度优化的衡量指标。优化后的多波长双向抽运方式不仅能保证对所有信道的平坦放大,而且其综合性能明显高于后向抽运方式。     

基于拟合衰减差自补偿的分布式光纤温度传感器

针对斯托克斯光和反斯托克斯光的本质损耗、附加损耗使分布式光纤温度传感器产生测温误差的问题,通过对分布式光纤温度传感器的温度解调原理的研究,提出了拟合斯托克斯光与反斯托克斯光之间衰减差的方法实现温度自补偿,以此减小测温误差.以传感光纤上不同位置的两部分作为参考段和测温段,参考段的光信号作为测温段拟合多阶衰减差和解调温度的参量,通过引入多阶拟合结果解调温度,减小因斯托克斯光和反斯托克斯光的本质损耗、附加损耗导致的温度误差,实现温度的初步修正.改变光纤上同一位置的温度,取3组不同温度值及对应信号值计算引入拟合衰减差前后的瑞利噪声,分析了瑞利噪声与光纤长度和温度的关系,通过引入拟合衰减差消除瑞利噪声,减小了斯托克斯光和反斯托克斯光的本质损耗、附加损耗导致的瑞利噪声误差,实现温度的再次修正.分析比较多阶衰减差拟合结果对测温误差以及消除瑞利噪声的影响,获得最优拟合阶次.在拟合因参考段的附加损耗而导致的测温段的附加误差后,通过拟合结果进行温度补偿,完成了最终温度修正.实验结果表明,在30-90℃,引入一阶线性拟合结果的温度修正效果最好,经过三次修正后,测温误差从10.50℃降低至0.90℃.     

Characterization of Rayleigh backscattering performance of CS-SSB signal in carrier distributed passive optical network

Rayleigh backscattering (RB) is an intrinsic phenomenon when light propagating in fiber and its level is fixed by the fiber type and the network configuration used. Thus, RB noise would be one of the major impairments in a carrier distributed passive optical network (PON). Previously demonstrated carrier suppressed subcarrier-amplitude modulated phase shift keying (CSS-AMPSK) modulation may be useful to effectively mitigate the RB noise. However, this modulation is basically a carrier suppressed double sidebands modulation (CS-DSB) format, in which the same information is carried by the two sidebands with equal magnitude. This is not very power-efficient for PON. Here, we further extend our RB studies by using carrier suppressed single sideband non-return-to-zero (CS-SSB-NRZ) modulation. We experimentally characterize the CS-SSB-NRZ modulation when subjected to both contributions of RB: Carrier-RB and Signal-RB. Then, numerical simulations are performed, and the results are in good match with the experiment. Finally, upstream transmission experiment is performed showing the feasibility of using the CS-SSB-NRZ signal for the carrier distributed PON. The RB performance of the SSB-NRZ signals transmitted at different distances and driven at different radio-frequency (RF) f_s is also investigated.     

Full investigation of the backscattering in resonator fiber optic gyro

Resonator Fiber optic gyro (RFOG) is a high accuracy inertial rotation sensor based on the Sagnac effect. The optical fiber ring resonator (OFRR) is the key rotation sensing element. The backscattering characteristics of the OFRR are fully investigated. The Rayleigh backscattering dominates the backscattering spectrum with the input power below the threshold. High carrier suppression is crucial to reduce this Rayleigh backscattering error. Being different from the intrinsic Rayleigh scattering of the fiber, the stimulated Brillouin scattering (SBS) in the OFRR should be avoided. This is because the finesse and the resonance notch depth of the OFRR decrease for the pump depletion through the SBS process. The shot noise limited sensitivity (SLS) of the RFOG is improved by increasing the input power. Through analysis, it is found that the threshold input power is improved after phase modulation. The SLS of the RFOG is analyzed at different modulation parameters and its relevant SBS threshold. Accordingly, the optimized modulation frequency and the corresponding maximum input power are all obtained. A simple method of testing the frequency shift in the SBS is also proposed. In this method, the central frequency of the laser source is locked to the resonance frequency of the OFRR in one direction. A steady SBS light is observed and its frequency shift is measured together.     

瑞利布里渊光时域分析系统中电光调制器的理论模型与实验研究

瑞利布里渊光时域分析系统能够以非破坏性方式实现单光源、单端工作,利用强度型电光调制器同时调制脉冲基底和脉冲信号是获得该系统所需连续光和脉冲光的关键技术.本文理论分析、仿真和实验研究了一种将脉冲信号输入到电光调制器偏置端、微波信号输入到电光调制器射频端同时调制脉冲基底和脉冲信号的新调制方法,探讨了电光调制器用于瑞利布里渊光时域分析系统时的最佳工作点问题.结果表明,当调制脉冲基底和脉冲时分别将电光调制器偏置在传输曲线的谷点和峰点,并根据实际系统的组成和性能指标要求选择合适的微波调制信号幅度,可获得满足瑞利布里渊光时域分析系统要求的连续光和脉冲光.本文的研究结果为瑞利布里渊光时域分析系统的最佳化设计提供了理论依据.     

瑞利布里渊光时域分析系统中电光调制器的理论模型与实验研究

瑞利布里渊光时域分析系统能够以非破坏性方式实现单光源、单端工作,利用强度型电光调制器同时调制脉冲基底和脉冲信号是获得该系统所需连续光和脉冲光的关键技术.本文理论分析、仿真和实验研究了一种将脉冲信号输入到电光调制器偏置端、微波信号输入到电光调制器射频端同时调制脉冲基底和脉冲信号的新调制方法,探讨了电光调制器用于瑞利布里渊光时域分析系统时的最佳工作点问题.结果表明,当调制脉冲基底和脉冲时分别将电光调制器偏置在传输曲线的谷点和峰点,并根据实际系统的组成和性能指标要求选择合适的微波调制信号幅度,可获得满足瑞利布里渊光时域分析系统要求的连续光和脉冲光.本文的研究结果为瑞利布里渊光时域分析系统的最佳化设计提供了理论依据.     

Resonator fiber optic gyro using the triangle wave phase modulation technique

Based on the Sagnac effect, resonator fiber optic gyro (R-FOG) has potential as a high accuracy inertial rotation sensor. An R-FOG based on the triangle wave phase modulation technique is proposed in this paper. The slope of the demodulation curve near the resonance dip is found to affect the ultimate sensitivity of the gyro. In order to maximize the slope of the demodulation signal, the parameters of the triangle wave are analyzed. By employing Fourier series and the method of field overlapping, the relationship between the demodulation signal and the resonance frequency deviation is analyzed. The optimum values for the modulation frequency and phase modulation index are obtained. And the relationship between the carrier component and the phase modulation index under analysis in this paper shows that the triangle wave phase modulation technique is more advantageous than the traditional modulation technique in reducing the noise induced by backscattering.     

Coherent CW image amplifier and oscillator using two-wave interaction in a BaTiO3-crystal

A BaTiO₃ crystal was used to amplify an image illuminated by an Ar-laser. The amplification mechanism is two-wave mixing in an electrooptic crystal, usually called dynamic holography. We achieved gain factors of 4000 with pump powers of 150 mW and holographic resolution. As the interaction between signal and pump wave is not effected through excited states of the crystal, the amplification process is virtually noise free. This has to be traded in with slow response, 0.1-1 s. To demonstrate the high optical quality of the amplifier, it was incorporated in a ring resonator as gain medium. It was possible to excite pure discrete transversal modes of higher order. That reveals the high optical homogeneity of the crystal over the mode cross-section of > 1 mm. The coupling process of the pump with the two counter-propagating waves forming the standing resonator wave is not symmetric. Consequently a travelling wave develops in the resonator.     

Experimental study on the imaging of the squeezed state light at 1064 nm

Stable, low noise, infrared squeezed state tight at 1064 nm is generated by utilizing optical parametric down-conversion (OPDC) technique based on periodically poled KTiOPO₄ in a optical parametric amplifier (OPA) resonator. A non-classical noise reduction of 2.58 dB below the shot noise is observed through balanced homodyne detection. The squeezed state light is used to set up an imaging system for high-resolution imaging, and it is found that the resolution of image based on the amplitude-squeezed light is 1.26 times larger than that of infrared coherent light under the same intensity. The experimental results indicate that squeezed light is an important non-classical light, which can overcome the coherent laser shot-noise, the classical diffraction limit and limit of quantum noise.     

Optical scattering noise in high Q fiber ring resonators and its effect on optoelectronic oscillator phase noise

Nonlinear phenomena occurring in an optical fiber ring resonator featuring ultrahigh Q factor are experimentally studied. The laser is locked onto the resonator, and the optical power induced in the resonator is controlled. The onset of the first stimulated Brillouin scattering wave occurs at an optical input power as low as -9 dBm in these resonators. When the resonator is used as the frequency reference device in an optoelectronic oscillator (OEO), it has been found that these parasitic signals mix with the OEO signal and degrade its phase noise. More than 20 dB improvement of the OEO phase noise has been demonstrated by limiting these nonlinear optical effects.     

Switching between positive and negative permeability by photoconductive coupling for modulation of electromagnetic radiation

We introduce a modulation mechanism for negative index materials (NIM) in the GHz frequency range by means of photoconductive coupling. This leads the way to a monolithically integrated modulable NIM achieved by conventional microfabrication techniques. The photosensitive material is deposited in the gap of the split ring resonator (SRR) structure and the response in terms of S-parameters is simulated using a high frequency structure simulator (HFSS^TM) program. Only a single SRR particle is simulated to demonstrate total suppression of resonance amplitude and without any loss of generality the concept is applicable to a NIM comprising of both negative permeability and negative permittivity. This simple modulation of refractive indices can lead to novel optical device developments with the potential to dramatically improve the performance of existing phased array antennas, optical beam-forming networks, antenna remoting and transportation of RF power through fiber. PACS 42.60.Fc; 42.82.Cr; 81.05; 73.50.Pz     

On the Development of Controllable Sources of Single-Photon States with an Orbital Angular Momentum on the Basis of Spontaneous Parametric Down-Conversion of Light

Methods for beam shaping with nonzero orbital angular momentum are studied using diffraction optical elements with the purpose of developing a source of single-photon states based on spontaneous parametric down-conversion of light in the LiNbO₃ crystal in the cavity resonator. The probability of the coincidence of the number of photocounts in detecting signal and idle fields under pumping by a beam with the orbital angular momentum is simulated.     

Effect of various parameters on working of all-optical Schmitt trigger

Schmitt triggers (ST) are well known and very widely used in the field of communications and signal processing techniques. It is robust, less sensitive to noise and is a building block in analog to digital converters. This work concentrates on all-optical Schmitt trigger for the purpose of using it in the field of optical modulation and signal processing. As the size of ring lasers is small these devices are best to use on a single integrated photonic chip. In this paper various dynamic effects of a binary Schmitt trigger is simulated and discussed. Control on various properties such as size of the ring, gain of SOA of a Schmitt trigger enables one to use it in developing all-optical devices.     

基于回波信号仿真的瑞利-喇曼-米激光雷达研制

 在分析瑞利、喇曼和米散射仿真回波信号的基础上,研制了一台探测大气温度、气溶胶和卷云的瑞利-喇曼-米散射激光雷达,实现了一台激光雷达针对大气温度、气溶胶和卷云光学特性的多参数探测。为提高瑞利和喇曼微弱回波信号信噪比,采用了极高灵敏度的R4632光电倍增管和光子计数技术;为实现对大气气溶胶和卷云的探测,532 nm回波信号采取高低分层技术、高层通道回波衰减方法和探测器门控技术。瑞利-喇曼-米散射激光雷达的探测结果证明了利用仿真回波信号指导激光雷达设计的可行性。