Simulation of distributed optical fiber disturbance detection system based on Sagnac/Mach-Zehnder interferometer and cross-correlation location

A distributed optical fiber disturbance detection system consisted of a Sagnac interferometer and a Mach-Zehnder interferometer is demonstrated. Two interferometers outputs are connected to an electric band-pass filter via a detector respectively. The central frequencies of the two filters are selected adaptively according to the disturbance frequency. The disturbance frequency is obtained by either frequency spectrum of the two interferometers outputs. An alarm is given out only when the Sagnac interferometer output is changed. A disturbance position is determined by calculating a time difference with a cross-correlation method between the filter output connected to the Sagnac interferometer and derivative of the filter output connected to the Mach-Zehnder interferometer. The frequency spectrum, derivative and cross-correlation are obtained by a signal processing system. Theory analysis and simulation results are presented. They show that the system structure and location method are effective, accurate, and immune to environmental variations.

Using a Mach–Zehnder interferometer to deduce nitrogen density mapping

This work presents an optical method using the Mach–Zehnder interferometer. We especially diagnose a pure nitrogen gas subjected to a point to plane corona discharge, and visualize the density spatial map. The interelectrode distance equals6 mm and the variation of the optical path has been measured at different pressures： 220 Torr, 400 Torr, and 760 Torr.The interferograms are recorded with a CCD camera, and the numerical analysis of these interferograms is assured by the inverse Abel transformation. The nitrogen density is extracted through the Gladstone–Dale relation. The obtained results are in close agreement with values available in the literature.

Temperature-induced effect on refractive index of graphene based on coated in-fiber Mach-Zehnder interferometer

The temperature-induced complex refractive index（CRI） effect of graphene is demonstrated theoretically and experimentally based on a graphene coated in-fiber MZI（Mach-Zehnder interferometer）. The relationships between real and imaginary parts of the graphene CRI and temperature are obtained through investigating the dip wavelength and intensity of the MZI interference spectrum changing with temperature, respectively. The temperature effect of CRI of the graphene is also analyzed theoretically. Both experimental and theoretical studies show that the real part and imaginary part of the CRI nonlinearly decrease and increase with temperature increasing, respectively. This graphene-coated in-fiber MZI structure also possesses the advantages of easy fabrication, miniaturization, low cost and robustness. It has potential applications in nanomaterial-based optic devices for communication and sensing.

Temporal and spatial evolution of air-spark switch plasma investigated by the Mach–Zehnder interferometer

An air-spark switch plasma was diagnosed by the Mach–Zehnder laser interferometer with ultra-high spatial and temporal resolution. The interferograms containing plasma phase shift information at different time were obtained. The phase shift distributions of the plasma were extracted by numerically processing the interferograms. The three-dimensional(3 D) electron density distributions of the air-spark switch plasma were then obtained. The working process of the air-spark switch was described by analyzing the temporal and spatial evolution of the plasma electron density.

A Novel Mach–Zehnder Interferometer Based on Hybrid Liquid Crystal–Photonic Crystal Fiber

We propose a novel all fiber Mach-Zehnder interferometer（MZI） based on photonic crystal fiber（PCF） filled with liquid crystal（LC）. The interference between the core mode and the cladding modes of a PCF is utilized.To excite the cladding modes, a region is formed using fiber fusion splicer. Due to the fact that varying effective index difference between the core region and the LC-filled cladding region can cause different transmission spectra,we mainly study the MZIs with different LC-filled structures and different lengths of LC filling. The measured results demonstrate that quite clear interference spectra can be obtained. Through analysis spatial frequency spectrum and temperature spectrum of two MZIs with different LC-filled structures, we can obtain that the MZI with adjacent two LC-filled holes has clearer interference spectrum and higher temperature sensitivity. Thus we choose this MZI to measure the temperature sensitivity with different lengths of LC filling. When the length of LC filling is 2 cm, the temperature sensitivities can be enlarged to 1.59 nm/C. The interferometer shows a good temperature tunability and sensitivity, which can be a good candidate for a highly tunable optical filtering and temperature sensing applications.

Phase precision of Mach–Zehnder interferometer in PM2.5 air pollution

This paper theoretically explores the effect of PM2.5 air pollution on the phase precision of a Mach-Zehnder inter- ferometer. With the increasing of PM2.5 concentration, phase precision for inputs of coherent state ＆ vacuum state and inputs of coherent state ＆ squeezed vacuum state will gradually decrease and be lower than the standard quantum limit. When the value of relative humidity is increasing, the precision of two input cases is decreasing much faster. We also find that the precision for inputs of coherent state ＆ squeezed state is better than that of coherent state ＆ vacuum state when PM2.5 concentration is lower. As PM2.5 concentration increases, the precision for inputs of coherent state ＆ squeezed state decreases faster, and then the two precisions tend to be the same while the concentration is higher.

Multi-ion Mach–Zehnder interferometer with artificial nonlinear interactions

We propose a method to implement a Mach-Zehnder interferometry based upon a string of trapped ions with artificial nonlinear interactions. By manipulating the coupling strength between two involved internal states of the ions, we could achieve the beam splitting/recombination with NOON states. Using current techniques for manipulating trapped ions, we discuss the experimental feasibility of our scheme and analyze some undesired uncertainty under realistic experimental environment.

Compact temperature-insensitive modulator based on a silicon microring assistant Mach-Zehnder interferometer

On the silicon-on-insulator platform, an ultra compact temperature-insensitive modulator based on a cascaded microring assistant Mach-Zehnder interferometer is proposed and demonstrated with numerical simulation. According to the calculated results, the tolerated variation of ambient temperature can be as high as 134 ℃ while the footprint of such a silicon modulator is only 340 μm2.

Theoretical Analysis and Experiment of Temperature Stability for Fiber-optic Mach-Zehnder Interferometer Filter

Fiber optic Mach Zehnder interferometer(MZI) can be used as wavelength multiplexers and demultiplexers. The △ L and △ directly influence the properties of MZI. To lengthen the △ L can demultiplex much more wavelengths, but when the △ L is longer, the temperature will influence MZI more seriously. A method to solve this problem is proposed, which enables MZI to work stably. The wavelength distance is 0.8 nm, and the extinction ratio is high.

Quantitative Visualization of the Thermal Boundary Layer of Forced Convection on a Heated or Cooled Flat Plate with a 30°Leading Edge Using a Mach-Zehnder Interferometer

This study focuses on the experimental measurements of the heat transfer coefficient over a flat plate with a 30° leading edge. Under forced convection by a hot/cold air and flow over a cooled/heated flat plate, the thermal boundary layer and its thickness are quantitatively visualized and measured using a Mach-Zehnder interferometer. In addition, the variation in the local heat transfer coefficient is evaluated experimentally with respect to the air flow velocity and temperature. Differences within the heat transfer performance between the plates are confirmed and discussed. As a result, the average heat transfer performance is about the same for the heated plate and the cooled plate under all air velocity conditions. This contrasts with the theoretical prediction in the case of low air velocity, the reason considered was that the buoyancy at the 30° leading edge blocked air from flowing across the surface of the plate.

基于Mach-Zehnder干涉仪的自相似激光器压缩系统设计

为了研究自相似脉冲在Mach-Zehnder干涉仪的压缩特性,采用非线性薛定谔方程对自相似脉冲的演化和压缩进行了模拟,分析了基于级联单模光纤的Mach-Zehnder干涉仪的光纤参数对脉冲压缩的影响。结果表明,在不考虑高阶色散的情况下,当上臂的两种单模光纤长度分别为8.16 m和2.16 m、下臂的单模光纤长度为8.16 m时,获得半峰全宽为27.85 fs、峰值功率为1860.59 W、基座能量比例为10.241%的最佳压缩脉冲;考虑高阶色散时,脉冲在单模光纤中传输呈现出峰值功率增大、基座增大的现象,且脉冲右移不利于输出基座较小的压缩脉冲;当3阶色散系数小于0.001 ps^(3)/km时,利用Mach-Zehnder干涉仪来压缩能获得质量较好的飞秒脉冲。该研究结果对于自相似脉冲的压缩研究具有一定的参考价值。

Noncontact ultrasound sensing based on Mach-Zehnder homodyne interferometer for photoacoustic imaging

We present a novel noncontact ultrasound(US)and photoacoustic imaging(PAI)system,overcoming the limitations of traditional coupling media.Using a long coherent length laser,we employ a homodyne free-space Mach-Zehnder setup with zero-crossing triggering,achieving a noise equivalent pressure of 703 Pa at 5 MHz and a-6 dB bandwidth of 1 to8.54 MHz.We address the phase uncertainty inherent in the homodyne method.Scanning the noncontact US probe enables photoacoustic computed tomography(PACT).Phantom studies demonstrate imaging performance and system stability,underscoring the potential of our system for noncontact US sensing and PAI.

全光纤Mach-Zehnder干涉仪及其在光纤自发布里渊散射测量中的应用

从理论上分析了全光纤 Mach- Zehnder干涉仪的分光原理 ,并将所研制的全光纤单通Mach- Zehnder干涉仪和双通 Mach- Zehnder干涉仪应用于自发布里渊散射光谱的测量 。

低功耗聚合物Mach-Zehnder热光开关

采用传统的半导体工艺制作了聚合物Mach-Zehnder型热光开关.利用扫描电镜观测波导形貌,通过红外摄像机观测波导的近场输出光斑,在通信波段1550nm波长下测试了器件的输出光谱.在电极上施加直流信号,测得热光开关的消光比为-15dB,驱动功率为16mW.引入直流偏置网络,获得了器件的开关特性曲线,经测量开关上升时间为1.2ms,下降时间为0.8ms.

基于Mach-Zehnder干涉仪的光纤入侵行为识别系统

为实现高精度识别功能,基于Mach-Zehnder光纤传感器建立光纤入侵行为识别系统。引入多元回归统计原理,建立常用信号特征参量与设定因变量之间的多元回归方程。通过逐步引入校验方法,验证回归模型的显著性校验,实现特征的优化选取。利用选取的有效特征,构造基于感知准则的入侵行为识别系统.实验证明基于多元统计原理的入侵行为识别系统具有良好的识别准确率,且识别准确率达到83.33%。

一个新型的基于全光纤Mach-Zehnder干涉仪BOTDR系统

报道了新型的分布式传感测量布里渊光时域反射 (BOTDR)系统 布里渊散射频移和强度均依赖于温度和应变 ,因此 ,BOTDR利用光纤中的自发布里渊散射作为测量信号可以实现分布式温度和应变测量 在BOTDR中 ,光源采用窄谱半导体激光器 ,并由声光调制器调制成脉冲光 ,经掺铒光纤放大器放大后 ,注入测试光纤以产生自发布里渊散射 利用双通Mach Zehnder干涉仪分离光纤背向散射中的自发布里渊散射与瑞利散射信号 ,实现了自发布里渊散射的直接检测 实验结果表明基于全光纤Mach

双Mach-Zehnder光纤干涉传感系统中的偏振衰落控制

针对偏振衰落现象导致信号关联的二义性使分布式双Mach-Zehnder光纤干涉传感系统难以实现高精度定位的问题,提出了一种控制偏振衰落的方法来保持系统检测信号的稳定性。利用系统的偏振模型分析了偏振衰落的来源,指出传感光纤偏振特性的不一致使系统检测信号对输入偏振态敏感是造成信号相关性恶化的根本原因,据此提出控制输入偏振态、搜索偏振态工作点的抗偏振衰落思想。在此基础上通过分析输入偏振态的两个参量对信号相关系数的作用进一步明确了偏振控制对算法的要求,并利用模拟退火算法进行了验证。现场实验表明,该算法可快速搜索偏振态工作点,持续稳定系统检测信号的相关性;结果证实了提出的偏振衰落控制方法可行且有效。

基于Mach-Zehnder干涉仪条纹成像技术的多普勒测风激光雷达鉴频系统研究及仿真

多普勒激光雷达在大气风场探测中已经得到广泛应用。相比于Fabry-Perot(F-P)干涉仪、Fizeau干涉仪,Mach-Zehnder(M-Z)干涉仪作为鉴频器具有透过率高、探测谱的范围宽、能进行视场展宽而获得大光通量、所成直条纹可以与CCD匹配等优点,同时也可以实现大的风速探测范围,弥补现有直接探测多普勒测风激光雷达探测范围较小,探测灵敏度的非线性问题。分析了基于M-Z干涉仪条纹成像技术的激光雷达大气风场探测原理,对干涉仪鉴频系统进行了参数优化设计及仿真分析,通过设定实验参数,获得仿真结果,进行数据反演,得到风速值与理论结果基本一致。

非平衡光纤Mach-Zehnder干涉仪偏振衰落及相位噪声分析

研究了非平衡光纤Mach Zehnder干涉仪因两束干涉光偏振态变化引起的偏振衰落和相位噪声问题。运用波导耦合理论和光纤偏振光传输理论,通过详细的推导,得到非平衡光纤Mach Zehnder干涉仪输出光强、可见度以及相位噪声的表达式,分析了干涉仪可见度、相位噪声与干涉仪输入光偏振态之间的关系,提出抑制偏振衰落和相移噪声的方法。