由於近年來全球暖化現象日益嚴重，為了人類未來的永續發展，除了目前能源減少浪費外，更需要尋找新的能源已減少對環境的汙染，而太陽能正是其中之一的可再生能源，目前有許多人都加入對太陽光的開發，其中有研究將自然光引入室內進行做為照明並提出自然光照明系統之設計，其有利於減少人造照明的使用和照明舒適性的要求，自然光照明系統藉由集光、傳光、放光子系統組合而成，集光子系統將收集的太陽光藉由傳光子系統傳遞至室內的放光子系統用於綠色照明，其過程中不需額外的能量轉換，能有效降低室內的用電量。
在傳統自然光系統中，其藉由光纖將光磚模組出口光線進行傳輸，然而一光磚模組擁有四個出光口，其需八根光纖才能進行耦合，其架設上難以將大量的光纖引導至同處，且易造成光纖彎折導致效率下降，本研究為自然導光系統(NLIS)提出一種新的光學耦合器設計，它採用全反射定理與雙拋物面共焦將光線二次壓縮，並針對出光口進行合併，藉由此概念減少光纖的使用，間接提升整體效率，而本研究的模擬結果顯示在理想光源的情況下串接五個耦合器時，仍達到65%的效率，且新式耦合器有效提升容忍角，在經過自然光系統目前2度發散角的準直器光源時比舊式耦合器效率高27%，相比舊式耦合器效率有顯卓的提升。

Due to the increasing global warming phenomenon in recent years, We need to reduce energy waste at present and find new energy sources to reduce the pollution to the environment for the sustainable development of mankind in the future, and solar energy is one of renewable energy. Many scholars have joined the development of sunlight. Among them, research has introduced natural light into the interior as a lighting and proposed the design of a Natural Light Illumination System(NLIS), which is beneficial to reduce the use of artificial lighting and lighting comfort requirements. The NLIS is composed of a light collecting, light transmitting, and light emitting subsystem. The collecting light system transmits the collected sunlight to the indoor light emitting subsystem through the light transmitting subsystem for green lighting. The system does not require additional energy conversion. It can effectively reduce the electricity consumption in the room.
In the traditional Natural Light Illumination System, the light brick module light is transmitted by the optical fiber. However, the light brick module has four light exit ports, which require eight fibers to be coupled, and it is difficult to guide a large number of fibers to the erection. At the same time, it is easy to bend the fiber, which will cause the efficiency to drop. This study proposes an optical coupler that would improves the couple efficiency of the daylight collecting module in the Natural Light Illumination System. It uses the law of total reflection and double paraboloid confocal to compress the light twice and combine it for the light exit. We use this concept to reduce the use of fiber and indirectly improve the overall efficiency. Our simulation results show that the multi-stage series connection still has 66% efficiency at the 5th stage, and the new coupler effectively raises the tolerance angle. The coupler which used Natural Light Illumination System light source maintain 76%, it is 27% more efficient than the old coupler, and has an outstanding efficiency compared to the old coupler.

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