本論文內容為介紹以光纖光柵(FBG)構成Fabry-perot干涉儀的入侵感測系統，透過環形共振腔來產生防區所需雷射光。系統共有四個防禦區域，四個防禦區域會回傳四種不同波長的訊號光，再透過光電偵測器(PD)和數據採集卡(DAQ)來進行後續的訊號處理。
本系統僅使用四芯光纜中的一條單模光纖，以光纜串接多個防區並作為感測器安裝在柵欄上，透過電腦可即時偵測四個防區干涉訊號的變化。系統中，四個防區是以分波多工的方式串接起來並獨立運行，再透過分析訊號可以得知防區使否遭受入侵。實驗中，我們分析訊號的方法是使用三種訊號參數，透過演算法計算出四個防區各自的閾值，當干涉訊號的三種訊號參數都超過防區各自的閾值時，系統才會給予警報。本論文研究的感測系統優點是僅需使用一條單模光纖即可作為感測器和訊號傳輸，再透過設計改善功率問題。

This thesis introduces fiber-optic perimeter intrusion detection system based on the use of Fabry-Perot interferometers for the perimeter zones. Specifically, each perimeter zone contains a Fabry-Perot interferometer with a pairs of fiber Bragg gratings used as end mirrors. Four perimeter zones are connected in series using a single SMF(single-mode fiber) with four pairs of fiber Bragg gratings distributed on the single SMF. The pair of fiber Bragg gratings for each perimeter zone have the same Bragg wavelength, while different pairs have different Bragg wavelengths, thus allowing four laser lights at different wavelengths to be used for intrusion detections at different perimeter zones. The lights emitting from respective fiber ring lasers are directed to their respective Fabry-Perot interferometers, and are sent back to respective photodetectors for intrusion detection. Once the SMF of the Fabry-Perot interferometer,i.e.,the SMF of the perimeter, is disturbed upon intrusion, the light received by the photodetector shows oscillation in optical power, and hence the photodetector gives an oscillating waveform at the output. By using a data acquisitim module, the four signal waveforms are loaded into a computer, which then gives three parameters, i.e., visibility, level crossing and frequency ratio for each detected signal for the four perimeter zones. The intrusion detection algorithm is then used to tell which perimeter zone is intruded by examining the three aforementioned parameters. We have tested the proposed four-perimeter-zone intrusion detection system at an outdoor environment, with extremely high alarm rate upon intrusion and zero mis- alarm rate for the case of non-intrusion.

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