鑒於全球性之能源危機，再生能源之利用為世界各國所重視，再生能源種類眾多，如太陽能、風力、水力、地熱、潮汐及生質能源…等。諸多再生能源中，以太陽能為最具有廣泛應用潛力之選項，其為地球上最充沛且乾淨之能源，假若我們可以最大限度的開發並利用太陽能，可降低能源危機對我們生活所帶來之衝擊。
本實驗室團隊所致力研究之自然光照明系統，係一充分利用太陽能之系統。有別於傳統太陽能電池將光轉電之太陽能利用方式，自然光照明系統不經能量轉換直接將太陽光導入室內做室內照明一途，減少了光電轉換過程中的能量損耗。
自然光照明系統可分為三個子系統:集光、傳光、放光子系統，在傳統系統中，集光系統與傳光系統間以光纖進行耦合。本篇論文提出一耦合器設計，此耦合器為一模組化之設計，可針對不同堆疊數之LightBrick模組進行耦合器串接動作，其目的在於減少光纖之使用量，以一5 x 5堆疊之LightBrick模組而言，應用此耦合器可減少80%之光纖使用量，此時之五階串聯耦合器耦合效率依舊高於光纖之耦合效率，為光纖之1.04倍以上；耦合器串接數為兩個以上時，耦合能量密度皆為光纖之1.5倍以上，此可大大減少耦合器出口之面積。減少光纖使用量可大幅降低施工難度及減少光纖使用成本。

Because of the energy crisis, renewable energy utilization becomes popular issue in countries around the world. There are many renewable energies such as solar, wind, hydro, geothermal, tidal and biomass energies ... etc. Among these renewable energies, solar energy is a potential one for wide applications. It’s an abundant and clean energy. If we can utilize solar energy as much as we can. It can reduce the seriousness of energy crisis.
This study is committed to develop Natural Light Illumination System (NLIS) for providing comfortable and healthy indoor illumination, which is a solar energy utilization system. Despite of the solar cell which utilizes solar energy with opto-to-electricity conversion, the NLIS guides light into indoors without energy conversion. It reduces the loss of energy conversion.
The NLIS can be divided into three subsystems which are light collecting, light transmitting and light emitting subsystems.In the conventional NLIS, it uses optical fibers to couple light collecting subsystem and light transmitting subsystem. This paper presents a coupler design for the NLIS. The coupler is a modular design; the coupler can be cascaded for stacked LightBrick modules. For a 5 x 5 stacked LightBrick module, using the coupler can reduce 80% fiber consumption and promote the performance of the NLIS. Reduceing the fiber consumption can reduce the engineering complexity and the fiber cost.

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