基于Φ-OTDR的动态纳应变定量测量技术研究

发布时间：2018-02-23 17:25

本文关键词： 纳应变测量动态测量分布式光纤传感相位敏感光时域反射计　出处：《哈尔滨工业大学》2017年硕士论文　论文类型：学位论文

【摘要】：近年来,随着人们在生产、生活中安全意识的提高,对桥梁、隧道、路基等建筑物结构健康监测的需求日益增大。其中,应变是一个相当重要的监测物理量,对于目前已有技术来说,应变分辨率普遍在微应变量级,难以满足某些特殊应用场合的需求,因此研究具有动态定量测量性能的纳应变传感技术具有重要的研究价值与广阔的应用前景。本文研究的动态纳应变定量测量技术是基于相位敏感光时域反射技术(Φ-OTDR)实现的,具有高精度、长距离、分布式测量等优势,可响应外界极微弱的应力或温度变化。本文具体研究内容如下:首先,从光纤散射的基本理论出发,详细分析了传统OTDR和Φ-OTDR的基本原理,通过建立理论模型,从散射光相位、强度两方面详细推导了Φ-OTDR的应变传感机制。其次,通过建立Φ-OTDR散射数学模型,对Φ-OTDR散射过程进行了数学仿真,同时分别对散射光相位、强度与应变的定量关系进行了仿真实验。仿真结果证明固定间隔下散射光相位差变化量与应变量之间存在线性关系,散射光强度标准差与应变量之间存在线性关系。最后,搭建了Φ-OTDR动态纳应变定量测量实验装置,通过外差探测和IQ解调对散射光的强度和相位信息进行实时解调。实验测定了散射光强度标准差与应变定量关系,通过增大样本数据长度减缓光纤各个位置处的应变灵敏度不一致性,此种方法所能达到的系统应变分辨率为6 nε。此外,本文提出通过测量固定间隔处的相位差来进行应变定量测量,这也是一种测量光纤应变折射率系数的新方法。实验测定所用的熊猫型保偏光纤折射率应变系数为-0.375ε-1,系统应变灵敏度为8.71 mrad/(nε·m),系统应变分辨率为1 nε/2 nε,分别对应5m/2.5 m空间分辨率。在此基础上对系统动态测量性能进行了研究,系统可响应频率为24 Hz,应变幅度为50 nε的三角波应变信号,同时也可响应频率为188Hz的光纤共振信号,证明系统具备动态纳应变定量测量的能力。
[Abstract]:In recent years, along with the people in the production, improve the safety awareness of life, on the bridge, tunnel, health monitoring roadbed structure increasing demand. Among them, strain monitoring is a very important physical quantity for the present technology, strain resolution common in micro strain level, difficult to meet some special applications application requirements, so research on nano strain sensing technology with dynamic quantitative measurement of performance has important research value and application prospect. This paper studies the wide dynamic strain measurement technology is a quantitative nano phase sensitive optical time domain reflectometry (-OTDR) based on the realization of the high precision, long distance, distributed mode and other advantages. Can be extremely weak response to external stress or temperature changes. The contents of this paper are as follows: firstly, starting from the basic theory of optical scattering, a detailed analysis of the traditional OTDR and -OTDR. The basic principle, by establishing the theoretical model, the light scattering phase, two aspects of strength are derived in detail with -OTDR strain sensing mechanism. Secondly, through the establishment of mathematical model of scattering phi -OTDR, Phi -OTDR scattering process by mathematical simulation, at the same time respectively on light scattering phase, the quantitative relationship between strength and strain experiments. The simulation results show that the linear relationship between the fixed interval under the light scattering phase variation and variable, the linear relationship between the scattering intensity and standard deviation should be variable. Finally, build the dynamic strain measurement with -OTDR nano experimental device, real-time demodulation intensity and phase information of the light scattering by heterodyne detection and IQ demodulation. The light scattering intensity of standard deviation and the quantitative relationship between the strain measured by strain increases the sensitivity of sample data length slow fiber at each location is not consistent, this Strain resolution method can reach 6 n. In addition, this paper presents the measurement of phase difference at fixed intervals for quantitative measurement of strain, which is a new method for measuring the refractive index of the optical fiber strain. Determination of the panda type polarization maintaining fiber strain coefficient is -0.375 ~ -1. Strain sensitivity is 8.71 mrad/ (n - M), strain resolution system is 1 N E /2 n e 5m/2.5 m, respectively. The spatial resolution on the basis of the research on the dynamic performance measurement system, response frequency is 24 Hz, the strain amplitude of triangular wave signal strain 50 N epsilon, at the same time can response frequency for optical fiber resonance signal 188Hz, proved that the system has the capability of dynamic strain that quantitative measurement of.

【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN253

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