【作者】 谭祺瑞；

【导师】 王智勇；

【作者基本信息】 北京工业大学 ， 光学工程， 2012， 硕士

【摘要】 传能光缆中的光纤一般是由纤芯和包层构成的，而且为了便于使用，包层外还有保护层。激光在纤芯中传输，纤芯的折射率大于包层的折射率，而包层中不应该有激光传输。光纤的数值孔径则由纤芯和包层的折射率共同来决定。光纤在传输高功率的激光时，在包层中传输的激光会损坏传能光缆。因为保护层会吸收包层中的激光，并产生热量进而烧坏光纤。这种在包层中传输的激光是由于激光在光纤入射端面发生散射而进入到包层中的，如光纤入射端面的划伤和灰尘就容易使激光发生散射。激光的入射角不符合光纤的数值孔径也会使激光进入到包层中。另外，灰尘吸收激光所产生的热量使得这种损伤的现象在光纤的输入输出端尤其严重。在输出端，加工工件的反射光会进入到包层中或照射到光纤的保护层上，这都会导致激光被包层吸收从而产生热量将光纤烧毁。本文研究了一种可用于传输高功率激光的传能光纤。该传能光纤采用有效的冷却系统，因而不会使激光损坏光纤。主要研究内容如下：1.光纤前端增加了石英端帽，这既可保护光纤端面又可方便光纤的固定。本文首先分析了石英端帽可承受高功率激光的工作原理，其优点如下：1)保护了入射端面2)便于光纤的固定3)输入输出端的防反射膜减少了反射损失其次本文设计了石英端帽的结构，并采用二氧化碳激光实现了石英端帽和光纤的低损耗高强度连接。2.采用模式剥离器清除包层中的激光，从而防止激光被涂覆层和保护层吸收。模式剥离器材料的折射率等于或大于包层折射率，这可使包层中的激光进入到模式剥离器中，最终转变为热量被冷却水吸收掉。本文计算了模式剥离器的尺寸大小，并设计了制作工艺流程。3.分析了传能光纤的损伤反馈机制，损伤反馈系统是由两层沿着光纤平行分布的铜金属层和外部电路构成。如果由于光纤损坏而导致高功率激光泄露出来烧毁铜金属层，外部电路就会切断入射光从而保护传能光缆。本文最后设计了光缆的接头和光缆的结构。更多还原

【Abstract】 An optical fiber cable includes a fiber which consists of a core and a surroundingcladding. To facilitate handling, the cladding should be surrounded by a protectivecovering. The radiation is conducted in the core whose refractive index is higher thanthat of the cladding. The cladding should be substantially free from radiation. Thenumerical aperture of the fiber is determined by this difference in refractive index. Inthe transmission of high power laser light, radiation in the cladding may cause seriousproblems, since it is eventually absorbed in the covering, resulting in considerableheat generation and damage to the fiber cable. Radiation in the cladding may arise asa result of light scattering in the end surface of the fiber, for example caused byscratches or dust particles, or as a result of some of the incident radiation quite simplyfalling outside the numerical aperture of the fiber. These problems are most severe atthe inlet and outlet ends of the fiber cable, where the absorption of dust particles,gives rise to the harmful heat generation. At the outlet end, radiation can be reflectedfrom the workpiece directly into the cladding or fall completely outside the fiber. Inboth cases, the radiation is finally absorbed in the covering and the heat is generated.The object of this dissertation is to provide an optical fiber cable for transmittinghigh power laser light without causing any damage to the fiber or its covering andhaving a more efficient cooling capacity compared to the previous designs. The mainidea is summarized as follows:First, the surface protection and mechanical fiber fixation of the quartz blockwhich can endure high power laser are analysed in this paper. In this way, we couldgain three main advantages:1) Procecton of the entrance surface2) Mechanical mounting of the fiber is made via the transparent quartz block3) Anti-reflex coating at the inlet and outlet ends of the quartz block, reducingthe reflection losses through the fiberAccording to this technology, the structure of the quartz block is designed. Incontrast to conventional heat sourecs for splicing, a new splicing prosess that a carbondioxide laser heats optical fiber and quartz block by radiation is adopted.Second, a modestripper solution is made to clean the cladding from the radiationbefore the buffer and jacket enter the fiber. By applying a moderstripper whosematerial has the same or slightly larger refractive index compared to the claddingmaterial, radiation can leak out of the cladding, and can be dissipated somewhere else,where it is easier to cool the radiation away. The diameter and the length of themodestripper are calculated, and the producing process is introduced according to theexperiment. Third, the breakage feedback system of the optical fiber cable is presented. Thereare two copper wires travelling parallel and close to the optical fiber. This means thatif a fiber breakage should appear and power which is high enough to cut the wires willleak out, the interlock circuit will be broken to protect the optical fiber cable. At last,the connector and the structure of the optical fiber cable are designed.更多还原