飞秒激光刻写高性能光纤布拉格光栅技术基础及应用研究

发布时间：2018-07-07 15:36

本文选题：飞秒激光 + 相位掩模板　；参考：《西北大学》2017年硕士论文

【摘要】：在石油测井领域,如何安全可靠的获取井中和井筒环境参数,对提高油气资源勘探和开发效率具有重要意义。光纤光栅传感器由于自身具有一些特殊的优点,能够承受井下极端的条件,因此,在光纤测井领域具有广泛的应用前景。本论文主要基于飞秒激光相位掩模板技术,在三种不同类型的光纤上写制了光纤布拉格光栅(Fiber Bragg Grating,FBG),并对其温度、高温应变、弯曲三种传感特性分别进行了实验研究。利用近红外飞秒激光结合相位掩模板技术,通过改变激光光斑的聚焦位置,在单模光敏光纤上刻写了三种不同类型的FBG,栅区覆盖光纤纤芯和部分包层区域,光栅透射光谱图呈现出两个分立的共振模式,分别为纤芯模式和包层模式。其中,我们选择包层折射率调制大于纤芯折射率调制的FBG进行温度测试实验。结果表明,包层FBG和纤芯FBG 一样具有很好的耐温性,且其温度响应灵敏度与纤芯FBG的几乎相等,因此也可用于高温场所温度变化量的监测。利用飞秒激光侧面照射技术,在经过载氢处理的多模光纤上刻写了三种不同类型的FBG。将激光聚焦在多模光纤纤芯的不同位置,会激发不同的光纤模式。当光斑位于纤芯中心轴时,仅纤芯基模被激发;移动光斑,使聚焦光斑偏离纤芯轴约10μm,多个高阶模式和纤芯基模同时被激发;继续移动光斑,当光斑偏离纤芯轴约20μm时,只有多个高阶模式被激发。仅有纤芯基模的FBG被用来进行高温应变测试实验。结果表明,温度越高,传感器应变灵敏度越高,最高可达5.24pm/με。因此,多模光纤布拉格光栅尤其适用于高温场所应变的监测。利用飞秒激光结合相位掩模板技术,通过将激光光斑聚焦在经过载氢处理的光纤纤芯与第一包层的界面处,在一种具有折射率下陷第一包层的四包层单模光纤上写制了 FBG,光栅结构覆盖光纤纤芯和部分第一包层区域。并且通过实验研究了光栅的弯曲和温度特性。弯曲试验结果表明,反射的包层FBG的强度对光纤微弯响应灵敏,且由于包层FBG在光纤横截面的不对称分布,弯曲响应具有很高的方向依赖性。但是,包层共振波长对弯曲不敏感,因此可以通过分别监测包层反射峰的能量和波长信息,来实现弯曲和温度的同时区分测量。多包层FBG的成功研制,对于结构健康的监测具有重大意义。
[Abstract]:In the field of petroleum logging, how to obtain the environmental parameters of well neutralization and wellbore safely and reliably is of great significance to improve the efficiency of exploration and development of oil and gas resources. Fiber Bragg grating (FBG) sensors can withstand extreme downhole conditions because of their own special advantages. Therefore, FBG sensors have a wide application prospect in the field of optical fiber logging. Based on femtosecond laser phase mask technique, fiber Bragg grating (FBG) is fabricated on three different types of fiber in this paper. The temperature, high temperature strain and bending characteristics of fiber Bragg grating (FBG) are studied experimentally. Using near infrared femtosecond laser combined with phase mask technique, three different types of FBGs were written on single mode Guang Min fiber by changing the focusing position of laser spot. The gate region covers the fiber core and part of the cladding region. The transmission spectra of the grating show two discrete resonance modes, one is the core mode and the other is the cladding mode. Among them, FBG with cladding refractive index modulation larger than core refractive index modulation is selected for temperature measurement. The results show that the cladding FBG has good temperature resistance as fiber core FBG, and its temperature response sensitivity is almost equal to that of core FBG, so it can also be used to monitor the temperature change in high temperature sites. Using femtosecond laser side-irradiation technique, three different types of FBGs have been written on the hydrogen-carrying multimode fiber. Focusing the laser in different positions of multimode fiber core excites different fiber modes. When the spot is located in the central axis of the core, only the core mode is excited; when the spot is moved, the focusing spot deviates from the core axis about 10 渭 m, and several higher-order modes and the core base mode are excited simultaneously; and the light spot continues to move, when the spot deviates from the core axis about 20 渭 m, Only multiple higher order models are excited. Only FBG with core-based mode is used for high-temperature strain test. The results show that the higher the temperature, the higher the strain sensitivity and the maximum 5.24pm/ 渭蔚. Therefore, multimode fiber Bragg grating is especially suitable for strain monitoring at high temperature. By using femtosecond laser combined with phase mask technology, the laser spot is focused on the interface between the fiber core and the first cladding after hydrogen transfer. FBGs are written on a four-cladding single-mode fiber with a first cladding of refractive index. The grating structure covers the fiber core and part of the first cladding region. The bending and temperature characteristics of the grating are studied experimentally. The bending test results show that the strength of the reflected cladding FBG is sensitive to the micro-bending response of the fiber, and the bending response is highly directionally dependent due to the asymmetric distribution of the cladding FBG in the fiber cross section. However, the cladding resonant wavelength is not sensitive to bending, so it is possible to measure the bending and temperature simultaneously by monitoring the energy and wavelength information of the reflected peak of the cladding. The successful development of multi-cladding FBG is of great significance for structural health monitoring.
【学位授予单位】：西北大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN253

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