【作者】 李卓轩；

【导师】 裴丽；

【作者基本信息】 北京交通大学 ， 通信与信息系统， 2013， 博士

【摘要】 摘要：基于光纤布拉格光栅(FBG)的光器件在高速光通信系统及物联网应用中发挥着重要作用。快速有效地获得单个或级联FBG器件的光谱特性,是优化设计基于FBG型光纤激光器、滤波器、放大器等各种光纤器件以及复杂分布式光传感网的重要基础和保障。本文采用V-I传输矩阵法(VITMM)对基于FBG的光器件特性进行了深入的理论和实验研究,理论分析并优化设计了全光纤声光光栅调制器,研究了准分布式FBG和啁啾叠栅两类级联光纤光栅检测系统的设计及应用。主要创新成果如下：1、首次建立了用于分析光纤光栅法布里-珀罗(F-P)腔谱特性的V-I传输矩阵模型,证明了该模型与常见的四种理论分析方法(类传输矩阵法、平行板干涉叠加法、递推法及多层膜法)相比,在理论分析和仿真计算光纤光栅法布里-珀罗腔反、透射谱特性时,能够在保证计算精度的前提下有效提高运算效率。2、采用VITMM,从谱线间隔与谱线数目、光栅反射率对谱线深度的影响、单纵模输出条件及阈值腔长三方面分析了分布布拉格反射(DBR)光纤激光器谐振腔参数对模式选择及激光输出特性的影响。分析了基于FBG的单腔谐振腔和双腔谐振腔两种类型光纤激光器的传输谱特性。制作了由均匀光纤布拉格光栅(UFBG)和啁啾光纤光栅(CFBG)作为谐振腔反射镜的DBR光纤激光器,实验获得的激光输出谱与仿真分析结果一致。3、针对FBG型超声探测,首次提出利用VITMM分析超声波的几何应变效应和弹光效应对FBG折射率分布以及周期的调制,获得了超声波波长与FBG长度比值变化对FBG反射光谱漂移的影响,所设计装置的声频率响应范围为15-1380KHz。4、采用三层均匀圆波导结构建立了单模光纤型声光光栅理论模型,并对其应变特性进行了实验验证。采用傅里叶模式耦合算法(FMC)获得了FBG型声光光栅在不同超声波频率及声致应变幅度下的反射谱,与传统计算方法相比,FMC算法可以有效提高运算效率。提出利用剪切模PZT产生纵向声波,具有较高的声光耦合效率。5、利用由1000个弱反射FBG构成的级联光纤光栅传感系统进行了温度测试,温度变化范围为40℃-150℃, FBG的温度灵敏度为10.7pm/℃。给出了当输入光功率一定时,不同FBG反射率下,任意FBG反射光功率及一阶串扰光功率与FBG个数的关系。提出了系统的信噪比优化方案,通过调整电光调制器的工作状态以及采用增加可调谐滤波器的方法,将系统的信噪比由5dB提高到15dB。分别采用移动相位掩膜板法和调节应力法实验制作了啁啾叠栅,其自由光谱范围可以通过改变相位掩膜板的位移量或者改变光纤轴向应力加以调节,其作为传感探头可实现温度、应力及应变等的检测。更多还原

【Abstract】 ABSTRACT:The Fiber Bragg Grating(FBG) based optical devices play an important role in the high-speed fiber optic communication system and the applications in Web of Things. Fast and efficient access to spectra performances of single or cascaded fiber gratings is the fundation to ensure optimizing the design of fiber laser, filter, amplifier, other fiber optic devices and complex distributed sensing network. In this thesis, the Ⅴ-Ⅰ transmission matrix method (VITMM) was presented to deeply research the characteristics of FBG based optical devices with theoretical analysis and experiment demonstration. The all fiber acousto-optic grating modulator was theoretically analyzed and experimentally optimized. The design philosophy and applications of two kinds of cascaded fiber grating testing system, quasi distributed FBG and superimposed chirped fiber grating, were introduced. The main achievements of this thesis are listed as follows.1-. The Ⅴ-Ⅰ transmission matrix model was firstly established to analyze the spectra characteristics of fiber grating Fabry-Perot(F-P) cavity. Compared with four common theoretical analysis methods(quasi transmission matrix method, parallel-plate interference superimposing method, recurrence method and multi-layer method), the VITMM can improve the computing efficiency under the premise of ensuring analysis accuracy when it was applied to simulate the reflection and transmission spectra of fiber grating F-P cavity.2、The VITMM was applied to analyze the influences of resonator’s parameters on the mode selection and laser output of Distributed Bragg Reflector(DBR) fiber laser in three aspects:the interval and number of spectral lines, the effect of grating reflectivity on the depth of spectra lines and the condition of single longitudinal mode output and threshold cavity length. Then the transmission spectra analysis of fiber grating laser with FBG based single-cavity resonator and double-cavity resonator was performed, respectively. The experiment setup of DBR fiber laser whose resonator was formed by a uniform fiber Bragg grating(UFBG) and a chirped fiber Bragg grating(CFBG) was carried out. The spectra of laser output in experiment was consistent with the simulation result.3、For the ultrasonic detection by FBG, the VITMM was firstly presented to analyze the refractive index distribution and the period change of uniform FBG caused by the geometric and strain-optic effect of ultrasonic wave. The relation of the shift of FBG reflected spectra with the ratio of the wavelength of ultrasonic wave to the FBG length was obtained, and the system was able to detect ultrasonic wave ranging from15to1380KHz.4、The theoretical model of single-mode fiber based acousto-optic grating was established by the three-layer uniform circular waveguide structure, and the strain performance was demonstrated experimentally. Fourier mode coupling(FMC) method was applied to achieve the reflected spectra of FBG based acousto-optic grating under various ultrasonic frequencies and acoustically induced strains. The FMC method can improve the computing efficiency effectively compared to tranditional computing method. A new way for generating longitudinal acoustic wave by shear-mode PZT, which has high acousto-optic coupling efficiency, was presented5、The temperature test was carried out by using a sensing system composed by1000cascaded FBGs with low reflectivites. The temperature ranged from40to150℃, and the sensitivity of FBG was10.7pm/℃. As the input optical power keeping the same, the relation between the returning optic power and the first-order crosstalk power of any FBG with FBG numbers, at various FBG reflectivities, was given. Two ways for optimizing the signal-noise-ratio of system were proposed:adjusting the working status of electro-optical modulator or adding tunable filter. After the optimization, the signal-noise-ratio of system was raised from5dB to15dB. The superimposed chirped fiber grating was fabricated by moving phase mask and adjusting stress, respectively. The free spectra range of that grating can be adjusted by changing the displacement of phase mask or the stress along the fiber axis. The superimposed chirped fiber grating can be used as a sensor employed in the measurement of tempreture, stress, strain and so on.更多还原