本論文利用簡單的光纖元件，自製一窄線寬脈衝雷射，並應用於相敏光時域反射儀的系統中，透過本實驗室自製環形共振腔雷射取代一般論文常使用的半導體雷射，大大的降低整體系統成本，並透過AOM調製產生的脈衝打進四點四公里的長光纖。我們將此脈衝打入感測光纖內，來產生背向的雷利散射。雷利散射也會因為光纖的震動或是拍擊所產生的相位變化而有能量強度的高低變化。利用此散射的強度變化，我們可以來推測出光纖中的斷裂、扭曲抑或是經由入侵引起之相位變化造成的干涉，即可反推出入侵訊號在光纖中的位置，以此來達到防區的效果。

In this thesis, an intrusion detection system based on phase-sensitive optical time domain reflectrometry is studied, with a lab-made ring resonant cavity laser used as a light sourse.
This laser exhibits a narrow linewidth of about 1KHz(FWHM), and its light is split into two parts,through a 10:90 fiber coupler, with the smaller part being a local oscillator light and the larger part the signal light injected into an AOM modulator to form a pulse train. The pulse train is launched into a test fiber of 4.4km in length.The Rayleigh backscattered light and the local oscillator light are then fed into a 50:50 fiber coupler and then balanced detectors.By a subtraction and mixer operation followed by low pass filtering, a detection signal train is generated. By using a moving average algorithm, we observe simultaneous intrusion points clearly enough with 1000 data windows processed in the algorithm.

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