本篇論文是利用DFB半導體雷射加上外部光纖雷射共振腔系統使其成為窄線
寬、單模態的雷射系統。將此窄線寬雷射經過聲光調變器調製成頻率為16kHz、寬
度為200ns的脈衝光，並將光放大之後打入5999.5公尺的感測光纖中，在225.45公尺、1740.99公尺、5824.17公尺處模擬入侵。由於同個脈衝波中不同位置的散射點因為相位不同而互相干涉產生震盪的波形，使得脈衝光在入侵處產生不同於未入侵處的雷利散射。我們利用光感測器(photodetector)接收反向雷利散射，將其光訊號轉為電訊號後，利用資料擷取卡將資料擷取至電腦。並利用移動平均法、相減法當作傳統處理方法，與本文提出的傅立葉轉換的新處理方法去做比較，最低提高了0.57dB，最高提高了1.15dB。

In this thesis , we present a method to create a narrow-linewidth single mode laser system using a DFB (Distributed-FeedBack) semiconductor laser combined with an external fiber laser resonator . The narrow-linewidth laser is modulated into a streamed pulsed light with a pulse frequency of 16 kHz and a pulse width of 200 ns through an acousto-optic modulator.
The modulated light is then amplified and injected into a 5999.5 m sensing fiber. The vibration source was added to the sensing fiber at the positions of 225.45 m, 1740.99 m ,and 5824.17 m. The Rayleigh backscattering lights from the non-invaded part and the intruded part are different, because the scattering points at different positions in the same pulse wave interfere with each other due to their different phases to generate an oscillating waveform. We use a photodetector to receive the Rayleigh backscattering lights and convert the light signal into an electrical signal, with a data acquisition card used to sample the backscattered traces. We use the moving average method and differential method, which are traditionally employed, to compare with the new processing method of Fourier transform proposed in this thesis. From the comparison, we observed that the improvement in SNR ratio would be from 0.57 to 1.15 dB by using the proposed method.

摘要 2
ABSTRACT 3
致謝 4
目錄 5
圖目錄 6
第一章 序論 8
1.1論文架構 8
1.2研究背景 8
1.3 文獻回顧 9
1.3.1光時域反射儀(Optical Time Domain Reflectometer) 9
1.3.2相敏光時域反射儀(Phase Sensitive OTDR) 13
第二章 實驗原理及數據處理方法 15
2.1背向雷利散射 15
2.2 數據處理方法 16
2.2.1移動平均法+相減法 16
2.2.2快速傅立葉轉換 17
第三章 實驗架構 18
3.1雷射架構 18
3.2 OTDR架構 19
3.3 光纖總長度推算 20
第四章 實驗結果 22
4.1雷射光源量測 22
4.2脈衝量測 25
4.3入侵模擬 26
第五章 結論 50
參考文獻 52

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