保偏光纤环形谐振腔研究

报道了一种用于角速度测量的光纤谐振式传感器保偏光纤环形谐振腔的研究,给出了测量的原理、实验装置和实验结果.根据计算和实验结果,对影响系统性能的几个重要光学参数进行了设计和优化.该谐振腔已在传感器系统中得到应用.     

保偏光纤保密通信研究

利用保偏光纤受到外界干扰时主轴发生变化，从而使其中传输的偏振光的偏振度发生变化的原理，实时检测介入窃听，给编码保密通信增加了一个保密度。由于是比例检出，信噪比高，抗干扰能力强。记录了无究听时系统在-3℃～60℃的背景噪声作为对比检出依据。检出窃听的阈值是裸光纤弯曲半径为8.5mm。     

保偏SiO_2光波导环形谐振腔温度特性研究

利用低压化学气相淀积(LPCVD)技术研制了Si基SiO2保偏光波导环形谐振腔,通过测试不同温度下的谐振曲线,得到了谐振腔双折射率差温度系数,进而利用琼斯矩阵法建立了谐振腔温度特性分析模型,分析了温度波动对谐振腔两个偏振态输出谐振曲线的影响。分析表明,研制的Si基SiO2保偏光波导环形谐振腔芯片具有较好的温度特性,能在较大温度范围内避免温度波动带来的两个偏振态谐振谷的重叠现象。     

光纤双折射和耦合器偏振性对环形腔的影响

本文应用琼 斯矩阵分析了光纤的线性双折射和耦合器的偏振性对光纤环形腔特性的影响,光纤的线性双白射和耦合器的偏振性使普通单模光纤环形腔带阻输出特性中的谐振峰分裂为两组,相应的谐振频率发生偏移,偏移量正比于双折射的大小和耦合器的偏振参数。两组谐振峰的相对幅度取决于输入偏振态。调整输入偏振态为Ｘ、Ｙ两线偏振态之一时,就仅出现一组谐振峰。环形腔的精细度与光纤的线性双折射无关,但爱耦合器偏振性的影响。     

Response characteristic analysis of polarization maintaining fiber ring resonator with dual-coupler for sensing application

A polarization maintaining fiber ring resonator with dual-coupler (PMDC-FRR) for sensing application is presented in this paper. Polarization maintaining directional fiber couplers and fiber loop are employed to eliminate the polarization fading in the fiber ring resonator. Three important characteristic parameters associated with the sensing application, which are the visibility of the output intensities, the free spectral range and the finesse, are discussed as functions of the coupler coefficients and the fiber loop length in detail. In addition, the critical drive voltage of the tunable laser to keep the output intensities stable is also analyzed, when the fiber ring resonator with dual-coupler is utilized as fiber sensor with phase modulation. A PMDC-FRR is designed practically in experiment with the power coupling coefficients of 0.5 and the loop length of 22 m. The experimental results provide sufficient arguments for the theoretical predicts. The theoretical and experimental analysis results will be useful to the sensing application of the PMDC-FRR.     

保偏光纤断裂形式分析

通过对于光纤断裂机理的分析,确认了目前影响保偏光纤的断裂两种形式,发现了不同于常规“延展性断裂”的“脆性断裂”,通过对于断裂形式的分析及研究,明确了“延展性断裂”与“脆性断裂”的差异,最终通过实验得到了“脆性断裂”产生原因及表现形式,对于保偏光纤应用过程中的机械损伤控制起到了指导作用。     

Optical transmission characteristics of fiber ring resonators

We present the results of an experimental investigation of the transfer characteristics of a fiber ring resonator for various values of the resonator finesse. In particular, we measure the spectral dependence of the intensity transmission and the induced phase shift in the undercoupled, critically coupled, and overcoupled regimes. We also demonstrate tunable optical (true time) group delay via a fiber ring resonator and show that a high finesse is unnecessary. Our laboratory results are in excellent agreement with theoretical predictions.     

保偏光纤拍长的测量方法

介绍了保偏光纤拍长测量的几种常用方法,就其测量原理,试验装置及优缺点分别进行了较为详细的分析和说明.并就目前多数测量方法适用于高双折射光纤的不足,介绍了一种较好的测量低双折射光纤拍长的方法.     

光纤双折射对光纤环保偏能力影响的实验研究

为了研究光纤双折射对陀螺光纤环保偏能力的影响,选用三种不同型号的光纤采用相同的绕制方法制作相同规格的光纤环.采用白光干涉仪测试光纤环的偏振耦合分布,并利用光纤环两端尾纤与白光干涉仪尾纤的熔点引起的偏振耦合干涉峰计算绕环光纤的双折射.通过不同光纤环测试结果的比较,分析绕环光纤双折射对光纤环保偏能力的影响.测试结果表明,三...     

Passive ring optical resonators with unidirectional stability

It is shown that low-loss passive ring optical resonators can possess unidirectional stability; i.e., in such resonators, a wave that is concentrated near the optical axis of the resonator and that exponentially decays in the directions perpendicular to the optical axis exists for only one of two senses of rotation.     

长波长细径保偏光纤的制作

通过介绍长波长熊猫型细径保偏光纤的制作工艺过程.分析细径保偏光纤制作的技术难点,初步解决了细径保偏光纤制作工艺中的问题,制作出了长波长熊猫型细径保偏光纤样品.所制作的保偏光纤在1550nm波长下损耗小于1dB/km,偏振串音达到近-28dB/km.     

基于白光干涉的光纤环保偏能力温度稳定性研究

为了研究陀螺用光纤环保偏能力的温度稳定性,采用白光干涉仪测试了光纤环在-40～80℃范围内7个温度点的偏振耦合分布。从光纤双折射、整体偏振耦合幅值、局部大偏振耦合点三个方面对测试结果进行了分析。光纤双折射随环境温度的升高线性减小,80℃时光纤双折射相对于-40℃下降了13.73%,说明了温度越高光纤本身保偏能力越低。整体偏振耦合幅值表现出了以40℃为最低点的抛物线形温度分布,说明了绕环胶固化温度是影响光纤环在宽温域整体外应力的主要因素。分析了换层处的大耦合点偏振耦合幅值在低温下出现高低间隔分布的原因是光纤环与结构件的粘接胶采用高温固化方法造成的。三个方面的综合分析表明,环境温度与光纤拉丝温度的差值是影响光纤内应力的主要因素,绕环胶和粘接胶的固化温度是影响光纤外应力的主要因素。测试分析结果为后续优化光纤环的保偏能力温度稳定性提供了参考。     

Tunable polarization maintaining fiber Bragg grating based OSNR monitor

A simple optical performance monitoring scheme based on a tunable polarization maintaining fiber Bragg grating is proposed. The proposed technique measures the in-band optical signal-to-noise-ratio through orthogonal polarization detection. The scheme is successfully demonstrated for NRZ-OOK signals at 10 Gb/s with an input dynamic range of around 20 dB. The results show that the performance of the scheme is not sensitive to the effects of chromatic dispersion.     

Analysis of four-port optical fiber ring and loop resonators usinga 3×3 fiber coupler and degenerate two-wave mixing

A theoretical analysis of four-port optical fiber ring and loop resonators using a 3×3 fiber directional coupler and degenerate two-wave mixing is presented. Expressions for the circulating (resonant) and output fields and intensities, as well as resonance conditions for two slightly different configurations of the loop resonator and for the ring resonator are obtained. It is found that the use of the degenerate two-wave mixing greatly improves the characteristics of these resonators. For example, the crosstalk of the ring or loop resonators when used as a wavelength division demultiplexer can be significantly deduced     

Tunable optical filters using compound ring resonators for DWDM

The device is based on a loop mirror in a ring resonator. The loop mirror allows tuning by changing the coupling coefficient of a directional coupler. The loop mirror is implemented using a Sagnac configuration to have the same optical path between the signals to be interfered (copropagating and counterpropagating ones). The filter structure allows optical integration for having higher free-spectral ranges. Simple design equations for the filter parameters and the tuning are reported. Measurements on a passive optical fiber tunable filter are presented. There is a good agreement between measurements and theory.     

High-performance optical wavelength-selective switches based on double ring resonators

In order to improve the performance of optical wavelength-selective switches based on double micro-ring resonators, an asymmetric intra-step-barrier coupled double strained quantum wells (AICD-SQWs) structure is utilized as the active light guiding medium. The AICD-SQW active layer has advantages, such as large change range in absorption coefficient, high extinction ratio, large Stark shift and very low insertion. For predicting the switching characteristics of double ring resonators structure, the absorption coefficient and real refractive index changes of the AICD-SQW active layer are calculated for different applied electric fields for TE input light polarization. Simulation results show that switching characteristics strongly depend on changes in absorption coefficient and real refractive index of active layer. In addition, isolations of 37.44 dB and 26.84 dB are realized between drop and through ports, when drop and through ports are ON and OFF, respectively, and vice versa.     

Four-channel switched microwave filter based on optical ring resonators

A four-channel switched microwave filter was demonstrated incorporating a switched optical resonator, which is constructed by integrating a 1 x 4 space switch with arrayed ring filters featuring different free spectral ranges. The four channels centred at 10, 16, 18 and 20 GHz were individually selected to provide a bandpass filtering via the control voltage applied to the switched resonator.     

Sagnac loop in ring resonators for tunable optical filters

General filter architecture using co- and counterpropagation signals are studied. A specific configuration based on a Sagnac loop within a ring resonator is analyzed. Novel tuning, apart from conventional tuning, is achieved by changing the coupling ratio of a coupler through the adjustment of the equivalent loop length. Full equations describing the filter behavior in passive and active configurations, and simple closed-form formulas to compute the tuning, tolerance, and full-width at half-maximum are reported. The performance of these devices is discussed for their application as selective or channel-dropping ultra-narrow-band filters. The effect of losses and their dispersion properties are also discussed. These devices can be conveniently implemented, using silicon- or InP-integrated optic technology, for they have high free spectral ranges.     

Anisotropic fiber couplers with nonaligned optical axes

Evanescent-type couplers composed of identical anisotropic cores with nonaligned stress axes reveal interesting propagation characteristics, such as power transfer occurring on two different length scales and reduced polarization holding capacity. The four normal modes have different propagation constants and electric field vectors which are skew to each other     

A broad-band single polarization optical fiber

The authors report on a single-mode optical fiber that transmits one and only one polarization state of the fundamental mode over a broad wavelength band (13%). The good broadband performance is attributed to the fiber's refractive-index profile, which mathematically allows only one polarization state to cutoff. The authors discuss general design principles and show that the mode field diameter is a qualitative indicator of the fiber's performance. The fiber's guided polarization state is similar to the fundamental mode of a step-index fiber in its low attenuation, 5.5 dB/km, and small mode diameter, 5.8 μm (both measurements at 840 nm). Most important, the fiber shows a broad single polarization band, 13%, a feature well described by the change in mode field diameter with wavelength of an ideal, circularly symmetry, W -profile fiber