多波长线性——谐振腔光纤激光源用于sagnac干涉测量滤波器和应变诱导尖脉冲过滤网

一个新型的多波长线性一谐振光纤激光源是利用一个应变诱导尖脉冲Bragg光栅，Sagnac干涉测量的滤波器制成，这种激光器和掺杂的铒—钇．光纤是首次提出并被实验验证的。这个Sagnac干涉测量滤波器是作为完全反射镜来使用的，它由一个保持偏振的定向耦合器和两个保持偏振的光纤元件构成。作为部分反射镜用的应变诱导尖脉冲Bragg光栅是靠弯曲一个均匀的FBG而得到的，     

保偏光纤转轴熔接Sagnac干涉环的光学游标效应及温度传感器

为了实现高灵敏度的温度传感,通过在基于保偏光纤Sagnac干涉仪的Sagnac环内增加一段保偏光纤,控制两段保偏光纤快轴熔接角度接近45°,设计并制造了保偏光纤转轴熔接Sagnac干涉环结构。在理论上通过Jones矩阵推导了保偏光纤转轴熔接Sagnac干涉环的干涉谱公式,基于仿真分析研究了主要参数对保偏光纤转轴熔接Sagnac干涉环输出特性的影响。仿真结果表明,保偏光纤转轴熔接Sagnac干涉环实现了光学游标效应,两段保偏光纤的平均长度、两段保偏光纤的长度差分别影响保偏光纤转轴熔接Sagnac干涉环输出干涉谱的波长间隔和包络周期;在实验中,将保偏光纤转轴熔接Sagnac干涉环应用在光纤温度传感器中。实验结果表明,在2cm的感温区域,保偏光纤转轴熔接Sagnac干涉环温度传感器的灵敏度就达到了-2.44nm/℃,是普通Sagnac干涉环温度传感器(-0.163nm/℃)的14.97倍。     

光信号传输中光纤偏振模色散的补偿

光信号传输过程中,光纤的双折射程度受传输路径和环境条件变化的影响,所产生的偏振模色散对于光信号的影响是随机的,因此对偏振模色散进行动态补偿十分必要.利用线性啁啾光纤光栅的双折射特性制成了时延补偿单元,具有体积小、插入损耗低、非线性效应低和成本低等优点,由外加电压驱动的压电传感器给出的可调谐的横向压力来获得可调谐的差分群时延,从而对光纤链路的偏振模色散实现动态补偿.     

光纤耦合器的性能分析

在光纤陀螺中,耦合器的性能变化对陀螺的稳定性有很大的影响,对光纤耦合器性能的分析研究对光纤陀螺的进一步发展具有重大意义。本文对耦合器分光比、损耗及偏振串音特性进行了理论分析与实验研究。基于LabVIEW和Matlab工具的发展和应用,结合两者的优点和实验室的设计需求,设计出了一个便捷、直观、实用性强的耦合器性能分析平台,通过该平台选取出了性能比较好的实验室自制耦合器,便于实际光纤传感系统中不同性能要求的耦合器的选取。     

应力诱导单模光纤双折射的研究

单模光纤在通常情况下可以认为是不存在双折射现象的.但当光纤受到弯曲、侧压及扭转时,由于光弹效应使得光纤分别产生了线性双折射和圆振双折射.该文对单模光纤由于各种作用产生的诱导双折射进行了论述,推导了不同情况下双折射的计算公式,并分析了其中的差别.同时,还初步分析了实际系统中对各种双折射效应的应用.     

干涉型分布式光纤传感系统抗偏振衰落性能研究

为了解决分布式光纤传感系统中常出现的偏振衰落现象,提高系统的稳定性,在分析了系统检测原理基础之上,基于单模光纤的双折射等效琼斯矩阵,建立了分布式光纤传感系统模型,明确了采用不同反射器件条件下,探测光强I与入射光偏振角度i的关系。通过试验证明系统采用旋转角为π/2的法拉第旋转镜(FRM)具有较好的抗偏振衰落特性。     

无端偏振控制器实验研究

在相干光通信、半导体激光放大器及某些偏振态调制光纤传感器中要求输入光偏振态稳定。本文分析了单模光纤受外应力作用所产生的应力双折射效应，并研究了采用四个光纤挤压器组成的无端偏振控制系统。     

数字式全光纤电流互感器系统建模与仿真技术研究

利用数字式全光纤电流检测系统抗干扰能力强、完全电气隔离等优点,在光纤电流传感器原理的基础上,研究了一种小巧的、适用于高压端大电流检测的基于法拉第磁光效应偏振态调制的数字式全光纤电流检测系统,改进了目前电力系统中使用的传统电磁式电流互感器。该研究应用保偏光纤有效抑制光纤中固有的线性双折射,使用琼斯矩阵对光纤系统进行分析,利用MATLAB仿真软件进行系统仿真,通过理论分析和系统仿真验证了由数字式全光纤电流互感器测得的电流值与电流的实际大小一致,所建立的系统数学模型和仿真模型正确可行。     

一种新型的光纤光栅波长解调系统

通过理论分析建立了扭转高双折射光纤的数学模型,提出一种利用扭转高双折射光纤实现光纤光栅反射波长的解调方法.理论和实验表明,该系统具有10nm的准线性解调制范围,线性度好,易于实现.     

基于变分理论的单模光纤耦合器应变特性研究

根据单模光纤耦合器的输出功率的比值对耦合区长度变化敏感的特点,仔细分析了熔融拉锥型光纤耦合器的应变特性.选用螺旋测微仪对光纤耦合器的应变特性进行研究,避免了悬臂梁结构自重、梁的振动等不可控因素对测量结果的影响,有效提高了测量精度.和电阻应变片的对比实验证明,熔融拉锥式单模光纤耦合器不但具有应力敏感性,而且随应变呈线性单调变化,同时具有较好的温度稳定性和横向抗干扰性.     

基于微纳光纤Sagnac环结构的光学电流传感器的响应特性研究

磁流体具有固体物质磁性及液体流动性的特性,且无本征矫顽力,无剩磁,磁场响应速度快,灵敏度高,将微纳光纤Sagnac环特殊的光传输性能与磁流体独特的磁光特性相结合,提出了一种基于磁流体包覆微纳光纤Sagnac环的全光纤电流传感器.理论推导了传感器的电流传感机理,设计了传感器的封装方法,并对传感器的温度特性和传感特性进行了...     

High sensitivity all-fiber Sagnac interferometer temperature sensor using a selective ethanol-filled photonic crystal fiber

An all-fiber Sagnac temperature sensor based on 3?dB tapered coupling and ethanol selective-filled photonic crystal fiber was demonstrated theoretically and experimentally. The ethanol selectivity-filled photonic crystal fiber has noncircular symmetry and thus exhibits birefringence. The ethanol selective-filled photonic crystal fiber, acting as the sensing element, was inserted in a Sagnac loop interferometer to measure temperature. The output spectra of Sagnac interferometer applied different temperatures were measured and analyzed. Experimental results have shown the temperature sensitivity of the Sagnac interferometer is 1.65?nm/°C in the range of 25–33°C.     

基于Sagnac的分布式光纤传感声学传感器

介绍了一种基于Sagnac的分布式光纤声学传感器. 这种声学传感器通过光电探测器、 数据采集卡、 滤波器和音频放大将3×3耦合器处干涉的光信号转换为电信号且实现音频信号的还原. 为了研究此分布式光纤声学传感器的性能, 分析了基于零频点实验声源扰动定位的原理, 并运用快速傅立叶变换将时域信号转化为频域信号显示声源扰动产生的零频点. 实验结果表明, 基于Sagnac的分布式光纤声学传感系统可以很好地实现声音信号的还原和定位.     

光纤迈克尔逊干涉仪的理论与应用分析

介绍了光纤传感器,特别是干涉式光纤传感技术的优点。给出了光纤Michelson干涉仪系统的结构。重点给出了光纤Michelson干涉仪系统中信号光与参考光干涉原理以及影响干涉光强因素的理论分析。详细阐述了单模光纤偏振控制器结构、工作原理以及其对光纤Michelson干涉仪系统传感臂偏振态的控制。最后,给出了光纤Michelson干涉仪系统的应用分析。     

Phase distortion analysis and passive demodulation for pipeline safety system based on Jones matrix modeling

Phase distortion happens in the distributed optical fiber oil and gas pipeline leak detection and early warning system, which results in decreased sensitivity of the system and bigger location errors. This paper studies the birefringent characteristic of the optical fiber interferometer sensing arm, and the Jones matrix model of the optical polarization is established. On the basis of this model the optical path and location principle are improved by using two 3 × 3 couplers to acquire four light signals. Then, the demodulation method is adopted to get phase differences induced by perturbation of the two reverse optical paths, which are used subsequently in cross-correlation algorithm to achieve the time-delay estimation. Compared to the method of polarization control, this approach simplifies the system structure and reduces the cost. The trial results show that this method not only eliminates the effect of the phase distortion but also improves the system’s accuracy and locating stability.     

Precision analog demodulation technique for open-loop Sagnac fiber optic gyroscopes

This paper presents an analog technique for the demodulation of interferometric fiber optic gyroscopes signals, based on the calculation of the mean value of the negative cycles of the measured photodetector signal from sinusoidally modulated Sagnac gyroscopes. The developed signal processing circuit was implemented and tested in a laboratory, and it was possible to detect signals as low as 5 microrad. Experimental results measured in a 890 m fiber optic coil gyroscope equipped with the developed circuit showed that the proposed circuit, when compared to the widely used and mature lock-in amplifier technique, presented a 5.1 dB higher signal-to-noise ratio. The circuit is also very stable with the temperature, since a very low drift of 0.04 degrees /h degrees C was measured in a complete gyroscope system. The Brazilian research sounding rocket VSB-30 is currently being equipped with the developed demodulator circuit.     

A 1.8-µm multiwavelength thulium-doped fiber laser based on a hybrid interference filter

A 1.8-µm tunable multiwavelength thulium-doped fiber laser based on a hybrid filter is proposed. In the designed ring-cavity fiber laser, the filter consists of one Sagnac loop and one dual-pass Mach–Zehnder filter. In the experiment, the lasing threshold is 155?mW, and a continuously tunable and stable single-wavelength laser could be realized with a minimum tuning interval of 2.1?nm within a scope of 22.5?nm. When an 1858-nm laser is obtained, the peak power fluctuation is less than 0.83?dB within 20 minutes at room temperature. By adjusting the polarization controller, stable dual-wavelength lasers are simultaneously achieved, and the peak power shift is less than 1.24?dB within a scan time of 20 minutes at room temperature. By changing the polarization state, stable triple-wavelength lasing is obtained, and the power fluctuation is less than 1.95?nm. In the experiment, the 3-dB linewidth of the laser is less than 0.4?nm.     

光纤陀螺用光学器件的匹配优化

针对光纤陀螺采用分立光学器件组装的特点,从光纤类型匹配、损耗匹配、偏振特性匹配几个方面讨论了对光纤陀螺精度的影响。给出了组成光纤陀螺各器件的理想匹配参数和光学器件的保偏尾纤连接时的对轴精度的优化,提高了光纤陀螺批量生产的一致性、稳定性、重复性以及光纤陀螺的性能。