本論文提出以同調偵測之方式量測光纖網路斷點位置的研究，透過接收反射之參考信號與待測信號彼此干涉產生的拍頻信號，即可即時偵測光纖的傳輸狀態。實驗部分，利用法布立-培若雷射二極體（Fabry-Perot Laser Diode）作為光源發送正弦波之掃頻信號進入光纖網路中，再分別以光循環器（Optical Circulator）將光纖網路中之反射光訊號回傳至光耦合器中（Optical Coupler）彼此干涉，最後使光偵測器（Photodetector）接收到之光訊號利用電光效應轉換為電訊號，偵測到之電訊號為時間的函數，透過分析信號強度隨時間之變化，並將時間轉換為光纖的長度，如此便可判斷光纖於傳輸網路中之斷點位置或熔接點所在，達成光纖傳輸特性之量測。與目前其他光纖量測模組特性比較，本論文設計之模組具有架構簡易、製造成本低的優勢，利於應用在實際光纖通訊系統中之生產與架設。

We present a method to measure the fault location in the optical fiber network based on the approach of coherent detection. The fault location monitoring of an optical fiber system can be achieved by measuring the interference signal that is formed by the reference signal and the test signal. In the set up, the Fabry-Perot Laser Diode is used as the light source to carry a frequency-sweep sinusoidal signal into the fiber-optic network. The signal can then be sent through the optical coupler divide the probe signal into the test signal and the reference signal. Using optical circulator to sent the reflect signal into the second optical coupler, where the two signal meet and interfere. Through the electro-optic effect of the photodetector the interfered optical signal is received and converted into an electrical signal that is time varying. By analyzing the signal intensity over time and converting it into the length of the optical fiber, the location of breakpoint or fusion point in the optical fiber network can be determined. The method we present has the advantages of simple architecture and low manufacturing cost. The features make it easier to produce and set up in the optical fiber communication system.

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