【作者】 韩庆荣；

【导师】 赵修建；

【作者基本信息】 武汉理工大学 ， 材料物理与化学， 2006， 博士

【摘要】 石英玻璃在可见光及近红外波段具有很高的透明性，此外，它还具有良好的化学稳定性和较高的机械强度以及通过掺杂能改变其折射率，因而石英玻璃成为制备光纤的理想材料。在四大光纤芯棒制造工艺中，PCVD工艺具有高精度的折射率分布控制、高沉积效率和极好的灵活性等特点，一直被公认为是制造多模光纤最好的工艺。本文首先在总结石英光纤研究现状的基础上，分析了石英通信单模光纤技术的未来发展趋势。通过理论分析和系列实验，对PCVD单模光纤的材料组成、结构和性能进行了研究和总结，以提高PCVD单模光纤的性能。本文研究的PCVD单模光纤的制造工艺流程包括PCVD沉积、熔缩、套管和拉丝等过程。PCVD单模光纤在芯层和光学包层中的材料组成为SiO₂-GeO₂-F-（Cl）。通过对各工艺的断面和剖面折射率分布进行对比分析，结果表明PCVD光纤具有材料均匀性好、折射率剖面控制精准的优点。为了确定PCVD光纤中的材料组成和结构设计，研究了掺杂对石英玻璃折射率、粘度和光纤衰减等性能的影响。采用玻璃纤维弯曲和高温拉丝测张力的方法可测试掺F和掺GeO₂石英玻璃的粘度。掺GeO₂和掺F均降低石英玻璃的粘度，在引起相同绝对值折射率变化时，掺F对玻璃粘度的影响是掺GeO₂的三倍。掺F除降低石英玻璃折射率外，还可降低PCVD玻璃中的OH^-含量。实验表明，在PCVD低水峰光纤中，芯层中的最佳掺F量为0.37wt％左右，包层中的最佳掺F量为0.67wt％左右。此外，研究表明PCVD所沉积的石英玻璃中的含Cl量随反应气体中O／Si的增加而降低。在PCVD工艺中，通过化学反应气体直接转变为玻璃，由于脱玻璃中少量OH^-难度较大，因此有效降低OH^-的措施在于前期预防。通过采用分子筛纯化器对原材料进行纯化、在PCVD沉积中利用C₂F₆脱OH^-、采用C₂F⁶和HF酸对表面OH^-污染层进行刻蚀以消除OH^-污染层以及利用大尺寸预制棒的稀释效应等能有效降低PCVD芯棒中的OH^-含量，使PCVD可用于制造低水峰光纤（LWP-SMF）。PCVD所制备的LWP-SMF各项指标均达到或优于ITU推荐的G.652C／D和IEC 6093-2-50B1.3光纤标准。为了探讨光纤中的缺陷对光纤性能的影响，在简单分析石英玻璃结构的基础上，介绍和分析了氢损产生的机理和测试方法。研究表明，加速测试氢损可通过增加H₂的分压（浓度）和提高反应温度来实现。其中使用热加速氢损测试，在0.01atm的H₂，70℃的测试条件时，可大大缩短氢损的周期，实验表明8-20小时的氢损过程是适宜的。使用热加速氢损测试，在8-20小时的氢损过程中，对1240nm造成的附加衰减在0.03-0.06dB／km左右。热加速氢损测试结果表明，PCVD单模光纤中存在NBOHCs和Si-E’缺陷，但Si-E’缺陷会自行愈合。实验表明，光纤的氢损随拉丝速度的增加而增大。氘气处理低水峰光纤，可有效减小乃至消除光纤在1383nm处的氢损。且这种抗损性能不随时间的增加而弱化，表现出良好的稳定性。为了通过波导结构的优化设计以提高PCVD单模光纤的性能，通过理论分析和计算，建立了粘度匹配模型。充分发挥PCVD的工艺优势，将光纤的波导结构设计和材料组成及结构设计有机的结合起来，是确保PCVD光纤优良性能的基础。在实现所设计的波导结构的同时，在材料组成和结构设计方面，采用GeO₂和F的共沉积，并遵循功能梯度材料的设计，在使各层粘度匹配的同时，热应力得到缓和，在光纤制造的后续工艺中，光纤中就不易产生残余热应力和断键，从而降低了光纤的PMD、提高了其抗氢损和抗弯曲等特性。将PCVD低水峰光纤制造技术、粘度匹配和功能梯度的材料组成和结构设计引入弯曲不敏感光纤的设计与制造，使光纤不仅在1260-1625nm具有低的衰减和良好的色散特性及抗氢损性能，还具有优异的抗弯曲性能。这种光纤在FTTH系统中不仅能与普通G.652光纤完全兼容作为信息传输介质，还可以用在器件上实现器件的小型化。此外，采用紫外截止的掺杂石英玻璃作为预制棒的部分外包，可有效阻止在拉丝过程中高能进入光纤芯层进而在光纤中产生的缺陷，从而有利于降低光纤的衰减和提高光纤的抗氢损等性能。更多还原

【Abstract】 Quartz glass has high transparency in the visible and near-infrared wavelength region. The chemical and mechanical durabilities of quartz glass are high and its refractive index can be changed by dopants. Therefore, quartz glass is the suitable material for optical fibers. Among the main four core rod fabrication processes, PCVD is considered as the best process for multi-mode fiber fabrication previously because it has high accuracy for RI profile control, high deposition efficiency and flexibility. In this thesis, the current situation of quartz fiber has been reviewed and the development trend of quartz single mode fiber （SMF） has been analyzed. Through analyzing in theory and series of experiments, the material composition, structure and properties of PCVD single mode fiber （SMF） have been researched and summarized in order to improve the properties of PCVD SMF.The PCVD based process for SMF fabrication includes PCVD deposition, deposition tube collapsing, RIT and drawing process in this thesis. The material composition in the core and optical cladding of PCVD SMF is SiO₂-GeO₂-F-（Cl）. Through studying the cross sections and RI profiles of the fibers fabricated by different processes, the results show that the advantages of PCVD fiber lie in its excellent material homogenization and high accuracy for RI profile control.To design the material composition and structure in PCVD fiber, the effect of dopants on the refractive index, viscosity and attenuation of quartz glass or fiber has been studied. The viscosity of GeO₂ and F doped quartz glass can be measured by fiber bending and drawing methods. The results show that both GeO₂ and F dopants reduce the viscosity. F has three times greater impact on viscosity than GeO₂ compared to the effects on the refractive index. F dopant can not only reduce the refractive index of doped silica but also reduce the OH^- content in PCVD silica. The test results show that the optimal F dopant level in the core and cladding is around 0.37wt% and 0.67wt% respectively in PCVD low water （LWP） SMF. Besides, the research result has shown that the Cl content in silica reduces with the increase of O/Si in reactants.The gaseous reactants are directly vitrified into dense glass layers on the inside of a fused silica substrate tube in the PCVD-based core rod production process. For the glass with little residual OH^- content （ppb）, it is difficult to dehydrate through drying process. Through purifying the raw materials by molecular griddle purifier, online purifying during PCVD by freon, using freon and HF acid to etch off the OH^- contamination layers and the dilution effect with large preform, the OH^- content in PCVD core rod can be reduced to very low level. PCVD process can be used for LWP-SMF production with these arts. PCVD LWP-SMF complies with or exceeds the ITU recommendation G.652 （C and D） and IEC 6093-2-50 type B 1.3 optical fiber specification.To study the effect of defects in optical fiber on the properties, the mechanism of hydrogen sensitivity and test methods have been introduced and studied. Acceleration test for hydrogen sensitivity can be fulfilled by increasing the H₂ partial pressure （concentration） and the reaction temperature. By adopting heat acceleration test, the circle of hydrogen sensitivity can be shortened at the testing conditions of 0.01atm H₂ with 70℃. The experiment results showed that the hydrogen sensitivity test circle is 8-20hours and the induced attenuation at 1240nm is around 0.03-0.06dB/km. From the test results of heat acceleration test, NBOHCs and Si-E’ defects were detected in PCVD SMF, but Si-E’ defects can automatically heal up.Test results have shown that the hydrogen induced loss increased with the increase of drawing speed. Using D₂ treating the LWP SMF, the hydrogen sensitivity at 1383nm can be reduced and even eliminated. Moreover, the hydrogen sensitivity resistance does not become weak later. The hydrogen sensitivity resistance is stable after D₂ treatment.To improve the properties of PCVD SMF by optimizing the waveguide design, the model of viscosity-matching for SMF has been set up through theoretical analysis and calculation. Making full use of the advantages of PCVD process and combining the waveguide design together with the material composition and structure design effectively are the basis for high-performance PCVD fibers. F and GeO₂ co-deposition and functional graded material （FGM） design are adopted and the viscosity-match is ensured for the material composition and structure design based on the determined waveguide design. The residual internal stress caused in the succedent fiber making process can be released. As a result, not only the residual internal stress but also the broken bonds caused by drawing process have been reduced, which can reduce attenuation, PMD and improve the hydrogen sensitivity resistance as well as microbending resistance properties.By adopting the LWP SMF fabrication techniques, viscosity match and FGM design in the design and fabrication for bending insensitive fiber, the fiber not only has low attenuation, nice dispersion property and hydrogen sensitivity resistance in 1260nm-1625nm but also has excellent bending resistance performance. Such fiber can be compliable with the standard single mode fiber and be acted as transmission media in the FTTH field. It also can be used to minimize the optical components.Besides, adopting UV opaque doped silica as part mechanical cladding for optical fiber preform can prevent the high energy, which may cause defects in optical fiber, going into the core of optical fiber. As a result, the attenuation can be reduced and the hydrogen sensitivity resistance property can be improved.更多还原