Few-mode Fiber Bragg Grating and its applications in sensor measurement

利用光纤传感器同时检测两个或多个参量是目前研究的一个热点，而光纤光栅由于其波长编码式调制的特性，在这方面的检测有着可靠、稳定、结构简单等等一系列优点，因而得到了广泛的应用。本文从光纤光栅的温度与应变响应入手，归纳了现有的一些温度和应力区分测量方案，并分析了这些方案的基本原理；接着本文根据少模光纤及渐逝场的特点，提出了一种新的同时测量双参数方案。首先从光纤光栅耦合模理论出发，模拟分析了少模光纤光栅传输模情况，结果表明在少模光纤光栅中传输的高阶模与基模对外界折射率变化有着不同的响应灵敏度，而对外界温度的变化则有着相近的响应灵敏度。然后将光纤Bragg光栅刻于少模光纤上，使此光纤光栅具有两个不同波长...In the near years, it’s a hotspot that how to detect two or more parameters simultaneously by fiber-optical sensors. As we all know, the fiber grating has so much excellence such as credibility、tranquilization、simple frame in this field because of its wavelength domain modulation. More and more people pay attention to it now. The article starts from the temperature and strain response of fiber Bra...学位：理学硕士院系专业：计算机与信息工程学院电子工程系_无线电物理学号：20023000

An alys is and Measurement on Refractive Index Sensing of Few Mode Fiber Bragg Gratings

中文摘要：理论分析和模拟计算了少模光纤布拉格光栅基模及高阶模的耦合与传输特性,得到在相同外部折射率变化情况下,少模光纤基模与高阶模耦合对应的布拉格波长变化,比正、反向基模之间耦合对应的布拉格波长变化显著增大。实验上制作了少模光纤布拉格光栅,测量了基模之间以及基模与高阶模之间对应的布拉格波长随外部折射率、温度变化的情况,得到与理论分析相符的结果。而对于温度变化对折射率测量结果干扰的问题,提出了通过计算布拉格波长差来克服温度影响的方法。这些结果为采用布拉格光纤光栅测量外部折射率变化提供了一种新的途径。英文摘要：The coupling and propagation characteristics of fundamental modes and high－orde r modes in the few mode fiber Bragg grating was numerically analyzed and simulated. It is indicated that the shifts of the Bragg wavelength corresponding to the coupling between the fundamental mode and the backward high－order mode is obviously larger than the shift of the Bragg wavelength cor responding to the coupling between the forward and backward fundamental modes . The few mode fiber Bragg grating was fabricated , and the variations of Bragg wavelengths corresponding to fundamental modes coupling and fundamental high－order modes coupling with external refractive index and temperature were measured. The experimental results agree with the theoretical analysis . Therefore by the means of Bragg wavelength difference calculation , the temperature induced fluctuation is overcome , which presents a new ray to measure the exte rnal ref ractive index change of fibe r Bragg gratings .基金项目: 国家自然科学基金(60177026) 、厦门大学985 项目和上海市重点学科建设项目( T0102) 资助课题

Variation-compensated of Bias Phase in Fiber M-Z Interferometers with Dual-wavelength Method

为克服原补偿方法在某些相位点的失效,提出采用双波长法,并进行了实验验证。实验中,固定一个波长,调整另一波长直至两波长达到特定间隔,此时在任意的偏置相位下均能获得没有衰落的补偿后的信号。实验结果表明,这种新的双波长补偿方法可以适合干涉仪偏置相位任意变化的情况,可有效地克服环境温度变化等因素引起干涉仪输出信号的衰落。A new dual-wavelength compensation method for the variation of bias phase in Mach-Zehnder(M-Z) interferometer was proposed and experimentally demonstrated.A none-fading compensated signal could always get when a space of two wavelengthes was specially selected by adjusting the one center wavelength of the two sources.As a experimental result,this dual-wavelength copensation method can work arbitrary bias phase as against the single-wavelength method.Thus it can effectively solve the signal fading problem of the interferometer,which may arise from the variations of enviromental parameters such as the fluctuation of ambient temperature et al.福建省自然科学基金资助项目(A0010004