光纖光柵色散特性量測及光柵結構之反推

Abstract

在本論文中我們以麥克森干涉儀量測光纖光柵的時間延遲，此方法的優點是快速、便宜，並可適用於反射式及穿透式的光學元件，而所需要的元件及設備則僅需寬頻光源、光譜分析儀、耦合器、反射鏡、及光準直器即可。寬頻入射光通過光纖光柵反射後會有不同的反射相位，而在頻域上產生干涉條紋，我們利用複立業轉換將此相位延遲解調出來即可得到此光纖光柵所造成的反射相位頻譜，再將相位對波長做微分即可得出時間延遲。 有了光纖光柵的反射相位及反射頻譜，就可利用離散剝皮法(Discrete Layer Peeling Method)將光纖光柵的耦合係數函數求出，可以用來確定曝照光纖光柵的製程準確性，或是用以提供我們此光纖光柵的資訊。

In this thesis we measure the time delay spectrum of fiber gratings by the use of a Michelson interferometer. The advantages of the method are the short measurement time and the low cost experimental setup. Both reflective and transmissive optical components can be measured and we only need standard components and setups including a broadband lightsource ,an optical spectrum analyzer,couplers, mirrors and collimators. The light emitting from the broadband lightsource enter the fiber grating and then be reflected.Different frequency components of the reflected light from the fiber grating obtain different phase shifts which can be infered form the change of the interference pattern on the frequency domain. We obtain the phase delay spectrum by performing a Fourier transform and by differentating the phase with respect to the wavelength we get the time delay spectrum finally. After obtaining the phase shift and reflectivity sprectra of the fiber Bragg grating we then use the “Discrete Layer Peeling Method” to find out the coupling coefficient of the fiber grating.The knowledge about the actual distribution of coupling coefficient can be used to achieve higher accuracy of the fabraction process and to provide us more information about the fabricated fiber gratings.