标题: 先进光纤光栅之制作与特性量测
Fabrication and Characterization of Advanced Fiber Bragg Gratings
作者: 庄凯评
Kai-Ping Chuang
赖暎杰
Yinchieh Lai
光电工程学系
关键字: 光纤光栅;干涉仪;fiber Bragg grating;interferometer
公开日期: 2003
摘要: 随着光纤光栅在光纤通讯及光纤感测领域被发现有越来越多的应用,致力于改善光纤光栅的制作与特性量测对于制作具有特殊光学特性的滤波元件而言就显得非常重要。在本论文中,我们利用逆散射之剥层(layer-peeling)法来设计先进的光纤光栅结构,并根据实验的实际制作架构,使用最小方差逼近(least-square fitting)法来找出最佳的光纤光栅曝照参数。
在制作具有复杂结构之先进光纤光栅方面,我们提出了三个新的制作光纤光栅的方法。第一个方法我们称之为偏振控制双光束干涉法,第二个方法称之为偏振控制相位光罩法,这两个制作方法目的都是利用曝照光束偏振的特性,在制作光纤光栅逐段曝照过程中既可以任意控制光栅折射率(ac-index)的大小,同时又可以保持光栅不同位置的平均折射率(dc-index)为定值。藉着利用这些方法,具有低损耗及良好频谱响应的滤波元件可以顺利的被完成。第三个方法是干涉式侧向绕射光栅位移监控的技术,我们提出这个光学监控方法来制作具有较长长度的光纤光栅元件。我们成功完成一些实验的例子来证明这些方法的可行性,也利用LabView的自动控制软体来建立自动化的光栅曝照系统,藉此可以提升光纤光栅制作过程的准确性及重复性。
在光纤光栅特性量测方面,我们发展光纤式麦克森干涉仪(the balanced Michelson interferometer)的方法及侧向绕射(side-diffraction)量测技术来分析光纤光栅完整的特性,包括光栅的复数反射系数及复数耦合系数等,这些系数代表着光纤光栅所有的光学和结构参数。当我们再结合逆散射之剥层法反推时,光纤光栅不同位置的平均折射率变化也可以求得。对未来先进光纤光栅制程的改善工作,这些特性的分析方法希望能够有所帮助。
When the FBG devices begin to find a lot of applications in fiber communication and fiber sensing, it also becomes more important to further improve the FBG fabrication and characterization techniques for achieving more complex optical filter properties. In this thesis, in order to design the advanced fiber grating structures, the layer peeling inverse design method combined with the least square fitting method is developed. Based on these synthesis methods, the best experimental parameters for our sequential writing setup can be found.
For the fabrication of advanced fiber grating structures, we have also proposed three new exposure methods. One is the two-beam interferometer method with the polarization control, and another is the phase mask method with the polarization control. Both of them have the same purpose for achieving a controllable ac-index profile in a single scan, with the dc-index profile being kept constant during the scan. The spectral shapes with a steep edge, very low sidelobes, a flat top, and very little ripples can be achieved by the use of these methods. The third method is the interferometric side-diffraction position monitoring technique for writing long fiber Bragg gratings. Some examples are presented to demonstrate the feasibility of these methods. The automation of the exposure system has also been setup for enhancing the accuracy and repetibility of the fabrication process.
In order to determine the complete characteristics of the fiber gratings, we develop the balanced Michelson interferometer method and the side-diffraction technique. The characteristics to be determined include the measurement of the complex reflection coefficient and the complex coupling coefficient of the grating. When the discrete layer peeling method is combined with these two measurement methods, we can get all of the information about the grating structure including the dc-index change. In addition, this analysis process may also be helpful for improving the fabrication processes of advanced FBGs.
URI: http://140.113.39.130/cdrfb3/record/nctu/#GT008924809
http://hdl.handle.net/11536/78391
显示于类别:Thesis


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