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    Please use this identifier to cite or link to this item: https://tkuir.lib.tku.edu.tw/dspace/handle/987654321/74712

    Title: 光纖浸水感測器之設計及實現
    Other Titles: Design and realization of optical fiber sensors for water immersion detection
    Authors: 林宣宏;Lin, Hsuan-Hung
    Contributors: 淡江大學電機工程學系碩士班
    楊淳良;Yang, Chung-Liang
    Keywords: 光纖感測器;光時域反射儀;浸水偵測;Optical fiber sensor;optical time-domain reflectometer (OTDR);water immersion
    Date: 2011
    Issue Date: 2011-12-28 19:22:12 (UTC+8)
    Abstract: 光纖為網路傳輸系統之最佳傳輸媒介,可提供高速率及長距離的光訊號傳輸,因此光
    測器(Liquid Level Sensor),其主要用於裝設在單一處所的感測器,其感測器的表面容易因
    水膨脹導致光纖產生彎曲損耗, 並配合使用光時域反射儀(Optical Time-Domain
    Reflectometer, OTDR)觀察。但此種感測器浸水時之彎曲損耗卻高達10 dB,因此無法在
    所提出的反射式光纖感測器主要是由一般8 度斜角APC 端面光纖連接器及一塊透水-漫射
    反射材料,例如:美耐皿海綿(Melamine Sponge)。我們所設計的感測器可設置在任何
    APC 端面與美耐皿海綿構成一個感測介面,因為美耐皿海綿本身內部結構的關係,乾與濕
    會讓APC 端面與美耐皿海綿的介面處呈現不同的狀態,乾的接面因未浸水,內部結構較
    且呈現平滑光亮面,在APC 端面與濕美耐皿海綿的介面處則呈現鏡面反射,因此APC 端
    面8 度斜角造成反射光不易返回到光纖內而產生較大損耗,OTDR 所量到的脈衝高度也就

    Optical fibers have become the best network transmission media, providing
    high-speed and long-distance optical signal transmission, so they are also ideal for
    real-time, remote, and distributed sensing. Since many features make optical fibers
    excellent sensors, they can be used as a nerve system and are very suitable for plant and
    civil applications. A commercialized optical liquid level sensor is made up of an infrared
    LED and a phototransistor that need to be accurately positioned at the base of the sensor’s
    tip, which is unsuitable for deploying in optical fiber networks and susceptible to external
    factors such as dust depositing and improper mounting to affect its function. NTT R&D
    group developed a sensing apparatus based on the fiber bending mechanism to be used in
    optical fiber links for detecting water immersion of underground ducts. The water sensors
    implemented in the optical fiber links can always be monitored by an optical time-domain
    reflectometer (OTDR). However, such sensors present higher bending loss while they are
    immersed in water, and therefore water immersion occurring at overmuch premise
    couldn’t simultaneously be discovered.
    In this paper, we propose novel OTDR-based optical fiber sensors, which are especially
    suitable for simultaneous multipoint sensing. Belonging to the quasi-distributed branch
    topology, it will be helpful to reach its sensing ranges and to avoid the failure of sensing
    points introducing an interruption to the rear sensing networks. Once the branched sensing
    points are damaged or immersed in water, their relative states can immediately be observed from an OTDR, and then those sensing points can easily be located and repaired
    to facilitate the construction and maintenance.
    The proposed sensors, which possess low-cost, compact and easily do-it-yourself (DIY)
    features, normally present the diffuse reflection at the boundary between the two media of
    melamine sponge and 8-degree APC end facet. After water immersion, they instantly
    change into the specular reflection at this boundary. Owing to the diffuse reflection at the
    dry boundary, the pulse-height measured by the OTDR becomes higher while the incident
    light backscattered into the fiber becomes larger. However, under water immersion the wet
    boundary results in specular reflection; and the 8-degree APC end facet can largely
    suppress the reflected light back to the optical fiber, which leads to a large return loss to
    the sensor and reduces the pulse-height shown on OTDR. Here, the melamine sponge
    plays two key roles as a water impurity filter and a lightwave diffuser.
    Appears in Collections:[電機工程學系暨研究所] 學位論文

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