Abstract
自1980年代以來，側磨光纖已被用來製作各式各樣的光纖元件，如耦合器 ，極化器等．為了製作較好的光纖元件，對研究側模光纖內傳導模態特性 之方法，有必要進一步的探討．目前，有 Shaw 和 Sorin 等人提出的相 位速度量測法及液滴測試法．而本論文提出兩個方法來觀察光纖內傳導模 態的特性．第一個方法稱為稜鏡耦合法，基本上是延續相位速度量測法的 精神，第二種方法稱為光纖費比－皮洛特共振腔法．使用這兩種方法，對 各種不同光纖進行實驗．我們發現，對一般單模光纖而言，稜鏡耦合法只 能觀察 LP 模態．我們成功地使用稜鏡耦合法求出各個模態的有效折射率 值，並與理論結果比較． 使用光纖費比－皮洛特共振腔法，我們可以清 楚地觀察每個 LP 模態相對應的子極化模態．比較這兩種方法的實驗結果 ，發現 PANDA 光纖的彎曲半徑會影響光纖內傳導模態的損耗．除此之外 ，光纖費比－皮洛特共振腔法也可被用來驗證側磨光纖的微擾理論．關於 微擾原理的理論分析在本論文中將會做簡短的研究．我們使用各種不同微 擾源，如空氣流動，溫度變化和各種不同折射率液滴等對側磨光纖進行微 擾實驗．我們清楚看到側磨 PANDA 光纖的不同極化態相位延遲變化．比 較實驗結果與理論預測，我們成功的證實了微擾理論．據我們瞭解，以實 驗驗證微擾理論，為本實驗室首先提出．此外，我們結合了光纖費比－皮 洛特共振腔法和液體加溫法，成功地看到在液滴實驗過程中，從高折射率 區到低折射率區間，側磨 PANDA 光纖的模態變化的情形．最後，本論文 ，建議的一些相關的應用及進一步的研究方向． From 1980s, side-polished PANDA fibers have been used to make various fiber devices, e.g., couplers and polarizers, etc. To make better fiber devices, the methods of studying the characteristics of a guided mode in side-polished fibers need to be investigated further. At present, the phase-velocity measurment method which was proposed by Shaw and Sorin and the liquid-drop method were demostrated. Two methods were proposed to observe the characteristics of guided modes in fibers in this thesis. One method was called the prism-coupling method which basically the same as that of Shaw et al. The other method was called the fiber FP cavity method. Various fibers were experimentally examined by both methods. We found that only LP modes in ordinary fibers can be spatially seperated by the prism -coupling method. We successfully estimated the effective refractive index of each guided mode in fibers by this method and compared well with their theoretical results. Their corresponding polarized modes of each LP mode were carefully investigated by use of fiber FP cavity method. Comparing with two methods, we found that the bendind radius of PANDA fibers affected the loss of guided modes in our experiments. In addition, fiber FP cavity method could also be employed too check the perturbation theory for side-polished fibers. Theoretical analyses regarding these subjects were made in this thesis. We used different disturbed sources, e.g. air- flow, the change of temperature, and various oils as perturbations to side- polished fibers. The evolution of retardation between different polarized modes of side-polished PANDA fibers was clearly seen. Comparing experiemental results with theoretical predicts, we successfully saw the changes of the transmitted power and modal transition in side-polished PANDA fibers by combining the temperature-ramping and fiber FP cavity method. Finally, we suggested some related applications and related works in the further in this thesis.