此篇論文為光時域反射儀應用於分佈式感測系統。首先，使用自製的窄線寬光纖環形雷射，線寬約為5kHz，當作光時域反射儀的輸入光源，接著打到聲光調變器(AOM)，由訊號產生器設定16kHz的脈衝到AOM，調製出一個脈衝訊號，並經過一些光學元件，如ISO、EDF、BPF、WDM、OC，最後經過長約6km的感測端，其中在三個點，分別為225.45m、1.74km、5.82km的地方，我們捲約為10m的小環黏在鐵尺上去做拍擊光纖的動作，來做為模擬入侵的震動訊號，此時因為脈衝產生的雷利散射會因為光纖的震動或拉扯而產生相位變化，使得Optical Power會振盪，出來的雷利散射由DAQ接收，採樣速率為8MS/sec，再傳到電腦。訊號分析處理是由Python程式去跑，這邊選擇2000個雷利散射的trace，每個trace有500個點，相鄰兩個點的間距為12.5251m。因為光纖會以每0.2dB/km衰減，所以利用補償法將雷利散射的trace做補償，接著利用傳統的移動平均法與相減法，得到的SNR為2.12dB，然而，經過改良後的方法，可以使SNR提升到2.61dB。再加上平方法後，SNR分別得到5dB與3.01dB。最後，拿未補償平方法下的移動平均加相減法與補償法後平方法下的移動平均加相減法，來做比較，可以使SNR從1.76dB增加到5dB。

In this thesis, we talk about an application of optical time domain reflectometer to intrusion detection and location. First, we use a self-made narrow-linewidth fiber ring laser with a linewidth about 5kHz as the input light source of optical time domain reflectometer, and then send it to an Acousto-Optic Modulator (AOM) to have a stream of 16kHz pulses by applying a function generator pulse signal to the AOM. The pulses then pass through some components, such as ISO, EDF, BPF, WDM, OC and then a 6km long sensing fiber. In the study, we vibrate the sensing fiber at the positions of 225.45m, 1.74km, and 5.82km simultaneously. To slap the optical fiber, we roll a small ring of about 10m and glued it on an iron ruler in order to simulate the vibration signal of invasion at each position. Due to the vibration of the sensing fiber, Rayleigh scattering will produce phase changes, and the optical power will oscillate. Rayleigh scattering is received by DAQ with a sampling rate 8MS/sec, and then transmitted to the computer. Signal analysis and processing are run by a Python program. Here, we choose 2000 Rayleigh scattering traces, and each trace has 500 points, with the distance between two adjacent points being 12.5251m. Because optical fiber will attenuate in accordance with 0.2dB/km, we compensate Rayleigh scattering traces by using a compensation method. The traditional moving average method and differential method induce an SNR of 2.12dB. However, after using an improved method, SNR can be enhanced to 2.61dB. Adding a square method, SNR is increased to 5dB and 3.01dB respectively. Finally, we compare the SNRs obtained in the situations of uncompensated signals and compensated signals. We find that the square method can lead to an SNR 1.76dB (5dB) for the cases in which moving average method and differential method are used, while the uncompensated signals (compensated signals) are adopted for analysis.

目錄
摘要.................................................................i
ABSTRACT ...........................................................ii
致謝...............................................................iii
目錄................................................................iv
圖目錄...............................................................v
表錄..............................................................viii
第一章 序論..........................................................1
1.1 論文架構.......................................................1
1.2 研究背景.......................................................1
1.3 研究動機和目的..................................................2
1.4 文獻回顧.......................................................3
第二章 實驗原理......................................................10
2.1 雷射線寬的量測.................................................10
2.2 光纖損耗特性...................................................11
2.3 脈衝頻率和取樣率的關係..........................................12
2.4 雷利散射推算出距離位置..........................................14
2.5 補償法........................................................14
2.6 移動平均+相減法................................................15
2.7 改良式移動平均+相減法..........................................16
2.8 平方法........................................................18
第三章 實驗架構......................................................19
3.1 雷射架構......................................................19
3.2 Φ-OTDR架構....................................................21
第四章 實驗成果與討論................................................22
4.1 元件量測......................................................22
4.2 雷射光源量測...................................................25
4.3 脈衝量測和取樣率的設定..........................................27
4.4 演算法後的入侵結果.............................................30
第五章 結論.........................................................51
參考文獻............................................................53

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