【作者】 刘德福；

【导师】 钟掘；

【作者基本信息】 中南大学 ， 机械制造及其自动化， 2008， 博士

【摘要】 光纤连接器作为目前应用面最广、用量最大的光无源器件,其种类、结构形式十分丰富,随着光纤通讯对器件质量要求的迅速提高,目前普遍使用的制造工艺与技术都难以高水平适应,迫切需要更深层次地认识光纤连接器制造过程中的机理性、规律性科学问题,以期在制造技术上取得突破。本文依托国家自然科学基金重点项目《光纤器件的亚微米制造理论与关键技术》,针对光纤连接器制造中存在的问题,通过理论分析、试验测试以及有限元仿真等方法,对光纤结合界面上光波传输与畸变规律、光纤连接器端面研磨抛光工艺进行了研究,建立了光学原理与器件结构参数、制造精度、工艺参数的融合模型并找出了其中的量值规律。论文的主要研究内容及研究结果如下:（1）基于薄膜光学原理,建立了光纤端面之间间隙、表面粗糙度、变质层等制造因素影响光纤连接器性能的数学模型。研究表明,在消除光纤端面之间的间隙后,研抛变质层是阻碍提高连接器光学性能的最主要因素。（2）研究了连接器端面研磨抛光工艺与器件光学性能的关系。采用干涉仪、扫描电子显微镜（SEM）、非接触表面轮廓仪（WYKO）等,对连接器插针体端面形状、表面质量进行了观察,总结了工艺参数对连接器光学性能的影响规律,获得了一组较优的连接器端面研磨抛光工艺匹配参数。应用椭圆偏振光谱仪测试了光纤端面研磨变质层的折射率与厚度,发现用粒度分别为3μm、1μm、0.5μm的金刚石砂纸研磨引起的变质层折射率相比标准光纤提高了约4.4%、3%、2.5%,相应的变质层厚度约为0.167μm、0.09μm、0.063μm。由变质层反推计算得到的连接器回波损耗与直接由回波损耗仪测得的结果基本一致,证明所建立的连接器光学性能与制造因素关联数学模型正确。（3）研究了连接器端面研磨抛光时光纤材料的去除。应用光纤压痕试验找到了实现光纤塑性域研磨加工的依据,并根据Bifano法则,得到实现光纤由脆性去除转变到塑性去除的临界切深d_c=0.023μm;基于Hertz接触理论,建立了陶瓷插芯与光纤组合端面研磨加工时磨粒对光纤切深的计算模型,获得了实现光纤塑性域研磨的条件。通过扫描电子显微镜观察用不同粒度的金刚石砂纸研磨后的光纤端面,发现存在脆性断裂、半脆性半塑性、塑性等3种材料去除模式,在塑性去除模式下可获得高质量加工表面。试验结果与理论分析计算相吻合,为研究变质层形成的原因及有限元仿真奠定了基础。（4）研究了光纤端面研抛变质层的材料微观结构变化,查明了变质层产生的根本原因。基于红外光谱理论,以SiO₂玻璃光纤红外光谱特征峰波数与硅氧四面体[SiO₄]单元之间Si-O-Si键角之间的关系为基础,建立了光纤红外光谱1100cm^-1特征峰波数与分子体积及折射率的数学模型。应用显微红外光谱测试仪,对光纤研抛变质层进行了测试,与标准光纤的红外光谱1100cm^-1特征峰波数相比较,发现各种研抛工艺条件下的变质层红外光谱1100cm^-1特征峰波数均有不同程度降低,从而推论出变质层的微观结构变化为硅氧四面体[SiO₄]单元之间的Si—O—Si键的键角减小、分子体积被压缩,反映到宏观上即为折射率升高。变质层分子体积压缩程度及折射率增大幅度与研磨抛光工艺密切相关,从半精研磨、精研磨到湿抛光,光纤端面变质层的分子体积压缩率从约10%降低到约5%,变质层的计算折射率增幅与椭圆偏振仪测试结果一致,证明了光纤微观结构红外光谱测试模型的准确性。（5）对光纤材料在研磨时应遵循的屈服准则进行了研究,并应用有限元法对光纤端面研磨变质层的形成进行了仿真。根据研磨过程中光纤存在塑性剪切变形及不可逆体积压缩的变形特点,推论出研磨时光纤的屈服是等效剪应力与体积应力共同作用的结果,建立了计入体积应力引起不可逆体积变形为特点的光纤材料弹塑性本构模型。基于后向欧拉法,推导了光纤材料本构模型应用在研磨过程中的应力更新算法,借用通用有限元平台ABAQUS的用户自定义材料UMAT接口,编制出了相应的计算程序,并将该应力更新算法纳入到通用有限元分析系统中,应用于光纤研磨过程的仿真分析,模拟了变质层的形成。研磨变质层的体积压缩率及变质层厚度的有限元计算结果与试验测试结果基本吻合,证明所建立的光纤材料本构模型客观地表达了其在研磨时的规律,这对其它脆性材料塑性域加工的表面质量研究也有参考价值。本文的研究工作可以作为光纤器件设计与制造的理论参考,期望对光纤器件的发展有所裨益。更多还原

【Abstract】 Optical fiber connector（OFC）is the most typical optical passive device at present and its categories and structures are very rich.As optical fiber communication requires better quality devices,many problems about mechanisms and rules of lapping & polishing process for OFC manufacturing must be investigated more profoundly,and then make a breakthrough in the manufacturing technology of OFC.This dissertation was supported by NSFC key project "Sub-micron manufacturing theory and key technologies of Optical fiber devices".To address the problems about manufacturing process of OFC,the light-wave transmission and aberrance rules on the silica fiber link-interfaces and the lapping & polishing process for end-faces of OFC were investigated systematically by theoritical analysis,experimental study and finite element analysis,the syncretic models and numerical-value rules between optics theory and structure parameters,manufacturing precision and technologic parameters of OFC were established.The main innovative research works and conclusions are listed as follows:（1）Based on the optics theory,the mathematical models about optical performances of OFC and the air-gap between silica fiber end-faces. surface roughness,damaged-layer,were established.Results show:when the air-gap between silica fiber end-faces is eliminated,the damaged-layer of fiber end-faces induced by lapping & polishing process is the uppermost factor that counteracts improvement of optical performance of OFC,and restraining damaged-layer is an important approach for improving the optical performance of OFC.（2）The relationships between the lapping & polishing process for end-faces and optical performance of OFC were researched.After the endface geometry and surface quality of OFC were observed by interferometer,SEM,WYKO,the influence rules between the lapping & polishing process for end-faces and optical performance of OFC were summarized.Also,a group of optimal technological parameters of OFC end-faces lapping & polishing was obtained.The refractive indices and depths of damaged-layer were tested by ellipsometer,the refractive indices of damaged-layer increased about 4.4%,3%,2.5%comparing with the one of as-received silica fiber by lapping with 3μm,1μm,0.5μm diamond films respectively,and the depths of damaged-layer were about 0.167μm, 0.09μm,0.063μm respectively.The return losses by calculating according to damaged-layer were basically consistent with the ones obtained by return loss tester,which proved that the established models between optical performances of OFC and manufacturing process factors are correct.（3）The material removal modes of silica fiber during lapping & polishing the end-faces of OFC were studied.The matter of lapping process of silica fiber in plastic mode was found by indentation experiments,and according to the Bifano law,the critical cut-depth of brittle-plastic transition for silica fiber was calculated,namely, d_c=0.023μm;based on the Hertz contact theory,the calculation model of cut-depth which an abrasive imposed on silica fiber when the combination endface consisted of both ceramic ferrule and optical fiber machined by lapping process,was established,and the lapping process condition of silica fiber in plastic mode was obtained.The fiber surfaces topography machined by lapping process with different grain size diamond abrasive films were observed by SEM,it was discovered that there were 3 material removal modes when lapping silica fiber,namely,brittle-fracture mode, semi-brittle & semi-plastic mode,plastic mode.The experimental results reported here are consistent with the ones from theory analysis.（4）The changes on microstructure of the damaged-layer on silica fiber end-faces induced by lapping & polishing process were investigated, and the essential formation reason of damaged-layer was also discovered. Based on the infrared spectrum theory,according to the relationship between the wave number of infrared spectrum characteristic peak of silica fiber and the bond angle of Si-O-Si between the silicon-oxygen tetrahedron[SiO₄]cells,the mathematical models on the 1100cm^-1wave number of infrared characteristic peak and molecular volume,refractive index of silica fiber,were set up.The damaged-layer on silica fiber end-faces induced by lapping & polishing process were tested by micro infrared spectrum tester,comparing with the 1100cm^-1wave number of infrared characteristic peak of the as-received silica fiber,the ones of damaged-layer induced by various lapping & polishing process decrease, so,the bond angle of Si-O-Si of damaged-layer material decreases, accordingly molecular volume of damaged-layer is compressed,and the refractive indices of damaged-layer increase.The molecular volume compressing degree and refractive indices of damaged-layer nearly correlated with lapping & polishing process,from semi-fine lapping,fine lapping to waterish polishing,the molecular volume compressing rate of damaged-layer decreased from about 10%to about 5%,the increasing ranges of reractive indices of damaged-layer obtained by mathematical model were compared with the ones tested direct by ellipsometer,both were basically matched,which verified the accuracy of the testing models on micro-structure of silica fiber with infrared spectrum.（5）The yield criterion obeyed by silica fiber during lapping was researched,and the formation about damaged-layer on the silica fiber end-faces induced by lapping process was investigated by FEM.According to the deformation characteristics that there were plastic shear deformation and plastic bulk compression simultaneously on silica fiber end-faces during lapping,it was discovered that the yielding action of silica fiber is that both effective shear stress and bulk stress act together,and the elastic-plastic constitutive model of silica fiber to conduct the plastic bulk deformation induced by the bulk stress was established.Based on the back EULER law,the stress-update arithmetics of constitutive equations for silica fiber applied to lapping process were educed.The stress-update arithmetics were imported into ABAQUS（an universal finite element analysis software）through UMAT interface program,and the applied to the analysis of lapping course of silica fiber,simulating the formation about damaged-layer on the silica fiber end-faces.The simulating results of the bulk compressing rate and the depth of damaged-layer are found to be in good agreement with the experimental results,which proved that the established constitutive model of silica fiber can describe the real rule of lapping silica fiber process.The method can also provide some valuable reference for researching the quality of surfaces machined by plastic mode for other brittle material.The conclusions obtained in this dissertation can provide some valuable theoretic references for optical fiber devices design and manufacturing.It is also expected that the study can be benefit to the development of optical fiber devices.更多还原