近幾年來，光纖光柵(Fiber Bragg Grating, FBG)被廣泛的使用在光纖通訊系統以及光纖感測系統上，布雷格光纖光柵在最近的十幾年中快速地發展，其最主要的功能是做為光的濾波器。因為布雷格光纖光柵具有低損耗、不受電磁干擾、成本低廉等優點，所以在目前已經被大量應用在光纖通訊及光纖感測等方面。

這篇論文主要是在光纖光柵的參數合成和感測應用之理論研究與實驗證實。在結合基 因演算法與光纖光柵之反射強度頻譜，光纖光柵的參數和應變、溫度分布之應用被提出並利用實驗證明。在大部分的光纖光柵應用前，光纖光柵的內部參數必須要先得知。有很多方法可以重建光纖光柵的內部參數。 例如Layer-Peeling、Fourier Transform、Optimization Method等。這些方法對於不同形式的光纖光柵會有一些不同的限制。因此，這篇論文提出得到光纖光柵的內部參數重建的一種新方法。而且，重建光纖光柵的完整參數需要光纖光柵的複數反射頻譜(強度和相位頻譜)。從簡單的儀器像是光強度儀或者光頻譜分析儀等來獲得光纖光柵的反射強度頻譜是容易的操作。不過，獲得光纖光柵的反射相位頻譜卻是需要繁雜、困難的程序。常見獲得光纖光柵反射相位頻譜的方法包括常用的相移法(Phase Shift Technique)、干涉法(Interferometric)和相位重建演算法(Phase Reconstruction Method)等等，這些方法雖有一些優點，但是他們也在實際用途方面有一些限制。這篇論文所提出的參數重建方法也提供一種技術獲得光纖光柵的複數反射頻譜。這種方法利用兩個光纖光柵的熱調變反射頻譜配合基因演算法來的到光纖光柵的完整參數，再利用這些參數進而求出光纖光柵的反射相位頻譜。為了證明提出方法的正確性，我們提供了幾個模擬和實驗結果。

光纖光柵在近年成為光纖感測器系統的一個重要的元件。除了具有光纖感測器的優勢以外，光纖光柵最重要的是可以提供優秀的分波多工 (Wavelength Multiplexing)能力。在大部分光纖感測應用的過程中，光纖光柵所提供的是外界擾動量平均的訊息值。但是在很多應用中，不僅需要獲得擾動量(strain and temperature)的平均值而且需要獲得沿著光纖光柵長度上所感受的擾動量分布(strain and temperature distribution)。這些外界擾動量分布會使得光纖光柵反射波長呈現非均勻的分布，因此，光纖光柵將產生一錯綜複雜反射頻譜。這個影響同樣會造成相位頻譜的變化。一些文獻中提到許多方法可以得到光纖光柵上的外界擾動量的分布。在這裡，我們也提出一種新的光纖光柵配置可以來獲得沿著光纖光柵長度上的任意外界擾動量分布。

在這篇論文裡，我們提出一種基于兩個熱調變反射強度頻譜和基因演算法的光纖光柵參數合成法。這方法可能重建光纖光柵的內部參數例如光柵位置，週期，長度和折射率分布。在光纖光柵的參數重建之後，我們能使用這些參數來完成任意的應變和溫度分佈。

This dissertation addresses a wide range of theoretical and experimental issues relating to the parameter synthesis and sensing applications of fiber Bragg gratings (FBGs). Specifically, the dissertation develops novel methods for: (1) reconstructing the multiple parameters of an FBG using a genetic algorithm (GA), (2) sensing arbitrary strain distributions using a GA to inversely search two FBG reflection intensity spectra, and (3) sensing arbitrary strain and temperature distributions simultaneously using a modified GA to inversely search the intensity spectra of FBGs.

FBG applications generally require the parameters of the FBG to be known. Many methods have been proposed for reconstructing an FBG’s parameters, including the layer-peeling technique, Fourier transformation, optimization schemes, and so on. However, each method is generally better suited to the parameter synthesis of one particular type of FBG. Accordingly, this dissertation presents a novel, more general, method for the reconstruction of FBG parameters. Reconstructing the complete characteristics of an FBG requires its complex reflection spectrum to be known. Although the reflection intensity spectrum of an FBG is easily obtained using simple instrumentation such as optical power meters or optical spectrum analyzers, obtaining the phase response of the FBG is more difficult. Common methods for obtaining the phase response include the conventional phase-shift technique, interferometric approaches, phase reconstruction algorithms, and so forth. Although each method has certain advantages, they are all limited in some regard when applied in practice. Therefore, a principal objective of this dissertation is to develop a practical approach for obtaining a complete characterization of FBGs of various types. In the proposed approach, the complete set of FBG parameters, namely the grating position, grating period, grating length and index of modulation along the grating length, are extracted from two thermally-modulated reflection intensity spectra using a GA. The performance of the proposed method is verified through its application to a number of simulated and experimental problems.

FBGs have emerged as an important component in fiber sensor systems in recent years. Fiber gratings enhance the advantages of fiber sensor systems by adding a powerful wavelength multiplexing capacity. However, FBG-based sensing systems are limited in the sense that they typically provide information of the measurand (generally strain and temperature) only at the level of an average value over the length of the grating. In practice, however, the user is generally more interested in obtaining the distribution profile of the measurand over the FBG length rather than a simple average value. In an FBG, different grating sections reflect different wavelengths when the FBG encounters a non-uniform distribution of the measurand. The FBG therefore produces a complicated reflection spectrum since each section of the grating contributes predominantly at its local Bragg wavelength. This non-uniformity characteristic affects both the intensity and the phase spectra of the FBG.

Exploiting this characteristic, this dissertation develops two novel FBG-based sensing arrangements. In the first arrangement, arbitrary strain distributions are sensed by using a GA to inversely search two FBG reflection intensity spectra, while in the second, arbitrary strain and temperature distributions are sensed simultaneously by using a modified GA to inversely search the intensity spectra of four FBGs.

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