本篇論文探討的是利用相敏光時域反射儀(Optical time domain reflectometer)作為光纖感測的的用途。起初要製作出一個窄線寬環形摻鉺光纖雷射，它的線寬為4KHz。實驗步驟是將窄線寬雷射發出的光源經過聲光調製器(Acousto-optic modulator)調製成脈衝寬度為200ns的脈衝光，再經過摻鉺光纖放大後打入6公里的傳感光纖。並且對237.5公尺的位置處、1750公尺處以及5825公尺處進行拍擊的模擬入侵。會讓傳感光纖中入侵點的三個位置有較劇烈的振盪波形。讓脈衝在傳感光纖中形成與未入侵時不同的背向雷利散射。最後再將有入侵的瑞利散射訊號傳送到採樣速率為8M/sec資料擷取卡擷取數據，再輸出到電腦。利用演算法將2000張瑞利散射的圖形做疊加形成2000張的疊圖，且利用移動平均法(Moving average method)以及相減法等方法做訊號處理。進而偵測到三個入侵位置的訊號。再與之後的改良方法做比較以及得出更好的訊噪比。

In this thesis, we research about the use of phase-sensitive optical time domain reflectometer as optical fiber sensing intrusion detection. Initially, a narrow-linewidth erbium-doped fiber laser with a linewidth of 1.8KHz was formed. In this experiment, we first modulate the laser light into a train of pulses with the pulse width of 200ns by using an acousto-optic modulator, and then amplify the pulse light with an erbium-doped fiber amplifier before the pulse light launched into a 6-kilometer sensing fiber. and into a 6-kilometer sensing fiber. And we slapped the sensing fiber at the positions of 237.5 meters, 1750 meters and 5825 meters. The three positions of the intrusion point in the sensing fiber will induce severe oscillation waveforms. Finally, the Rayleigh back-scattering signal is sent to a data acquisition card with a sampling rate of 8M/sec to capture the data, and then inputed to a computer analysis. Using program algorithms, 2000 Rayleigh back scattering graphics are superimposed to form 2000 stacked traces, and the moving average method and differential method are used for signal processing. In this study, we use a new method in which a trace is obtained by averaging first 100 traces and is used for the first trace. Also, we compensate the loss in the computation to raise the Signal-to-Noise Ratio(SNR), It can be found that the detection SNRs are improved , especially for intrusions occurring at far sites.

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