布雷格光纖光柵具有許多應用，尤其是在光纖通訊與光纖感測這兩個領域。在光纖通訊領域，色散是一個很重要的特性。由於系統元件的折射率變動會隨著波長變化，因此導致光脈衝變寬，使得接受端訊號難以辯識，所以，色散在光通訊系統中是一項很關鍵的參數。在光通訊系統中，週期漸變型布雷格光纖光柵可以用來做色散補償。為了補償色散，事先了解週期漸變型布雷格光纖光柵的相位響應特性是必須的。因此，近幾年來，許多布雷格光纖光柵的特性量測技術已經被發展出來了。

　　在此篇論文中，我們結合基因演算法與兩個溫度調變反射強度頻譜來達成週期漸變型布雷格光纖光柵之相位響應重建。我們利用溫度分佈梯度來調變週期漸變型布雷格光纖光柵反射強度頻譜與結合基因演算法來合成布雷格光纖光柵之參數。當基板受到兩個已知線性溫度梯度分佈作用時，我們可以得到兩個作為基因演算法目標函數之不同的反射強度頻譜。之後，利用基因演算法來尋求最佳參數，再藉由所求得之參數，重建出週期漸變型布雷格光纖光柵之相位響應。

　　我們所提出的方法，不僅具有簡單，成本低，非破壞性的優點，而且還可以解決週期漸變型布雷格光纖光柵的週期方向性問題。最後，我們用週期漸變型布雷格光纖光柵來驗證這個方法的可行性。

　Fiber Bragg gratings (FBGs) had many applications, especially in optical fiber communications and optical fiber sensing. In optical fiber communications, chromatic dispersion is an important characterization, which broadens optical data pulses through the wavelength dependent on the refractive index variation of system elements, and becomes critical to system throughput. It is known that a chirped fiber Bragg Grating can be used for compensating chromatic dispersion in an optical fiber communication system. To compensate this dispersion, the phase response of the chirped FBG is needed. For this reason, many FBG characterization techniques have been developed in recent years.

　In this thesis, we report the use of genetic algorithm and two thermally modulated reflection intensity spectra for the phase reconstruction of chirped FBGs. We apply temperature distributions to modulate the chirped FBG’s reflection intensity spectra and combine a genetic algorithm to synthesize FBG’s parameters. Two different reflection spectra are taken as objective spectra from a FBG when the substrate is applied to two known gradient temperature distributions. Then we employ the genetic algorithm to search for the parameters which generate the calculated reflection spectra by applying a T-matrix analysis to the objective spectra. Thus from these parameters, we can reconstruct the phase response of the FBG.

　We have proposed a novel technique for phase reconstruction of chirped FBGs. The advantages of the proposed technique are simple, low cost, and nondestructive characterization. And this method can also resolve the ambiguity of chirped FBGs with opposite structures. One chirped FBG was used to demonstrate the feasibility and effectiveness of this technique. The experimental results have shown that the phase response of the grating can be successfully reconstructed.

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