| Abstract: | 我們設計並實現出運用變色油墨於光纖的感測器，非常適合架構於光纖網路中，用於浸水與溫度超載感測。
常見的光纖浸水感測器是基於光纖彎曲損耗機制，並由光時域反射儀監測。然而，此感測器浸水後具有相當大的彎曲損耗，因此無法在光時域反射儀上同時觀察到多個處所的進水狀況。一般來說，溫度型光纖感測器是稍微複雜且昂貴。
在本論文中，我們提出兩種基於光時域反射儀的光纖感測器，非常適合同時多點感測。將它們設置於準分佈分支網路中，進而形成網狀感測網路，延伸監測範圍且不因單一偵測點的故障或破壞而影響到其他的偵測點或是主幹光纖偵測線路的運作。一旦分支偵測點受損或浸水/溫度超載，它們相對應的狀態可立即由OTDR觀察，並且感測點可以輕易地定位及修復，有助於施工及維護。
所提出的感測器具有成本低、結構輕巧和易於自行製作等特色，主要是由8度斜角APC端面或平坦PC端面與厚度3mm的變色油墨材料組合而成，例如：濕敏變色油墨、溫敏變色油墨。因為變色油墨內部結構的關係，它通常呈現漫射反射狀態，容易讓反射光脈衝進入光纖，因此光時域反射儀可得到較高的脈衝高度。然而，當感測器處於溫度超載或浸水狀態，油墨變色且呈現透光狀態，導致漫射反射率減少，而感測器產生較大的返回損耗，光時域反射儀所量到的脈衝高度也就下降了。
We design and carry out the optical fiber sensors employing discoloration ink, which are particularly suitable for deploying in the optical fiber networks for water-immersion and temperature -overload sensing.
A conventional water immersion fiber sensor is based on the fiber bending mechanism, and it is monitored by an optical time-domain reflectometer (OTDR). However, such sensor immersed in water has a remarkably high bending loss. Thus, many events of water immersion occurring could not simultaneously be monitored by an OTDR. In general, temperature fiber sensors are somewhat complicated and expensive.
In this thesis, we propose two types of OTDR-based optical fiber sensors, which are especially suitable for simultaneous multipoint sensing. To install them in the quasi-distributed branch networks can form mesh sensing networks, reaching their sensing ranges and avoiding the failure of sensing points introducing an interruption to the rear sensing networks. Once the branched sensing points are damaged or immersed in water/overloaded in temperature, their respective states can quickly be observed from an OTDR, and then those sensing points can easily be located and repaired to facilitate the creation and maintenance.
The proposed sensors, which possess low-cost, compact and easily do-it-yourself (DIY) features, consist of a fiber connector with either 8-degree angled physical contact (APC) facet or physical contact (PC) facet and a 3-mm thickness of discoloration ink, for example, soaking discoloration ink and temperature discoloration ink. Because of the inner structure of discoloration ink, it naturally presents a state of diffuse reflection, easily leading the reflected light into the fiber; therefore, the OTDR can obtain a relatively high pulse-height. However, when the sensors were in a temperature-overload or water-immersion state, the ink changed its color and presented a transparent state, which leads to the reduction of diffuse reflection and produces a higher return loss for sensors to make the pulse-height measured by an OTDR decrease. |
