本篇論文在探討側面泵浦耦合器電磁場的耦合效率，及分析相關幾何參數對於最終功率耦合效率的影響，藉以最佳化元件設計。論文中使用Beam propagation method (BPM, Rsoft BeamPROP軟體)進行模擬研究。模擬開始前我們先透過Rsoft模擬軟體調整初始線性極化模態階數，計算出對應的初始光源進入多模光纖時的光子有效折射係數，最大模態階LP70,1是可以傳遞在我們所使用的多模光纖的極限值。再來我們為了符合我們實驗室較常使用的泵浦光源的規格，所使用的光源為雷射二極體(約95%光源的數值孔徑等於0.13，包含數值孔徑低於0.13的光源)，將其利用公式換算成光子有效折射係數後，得到模態階接近LP40,1，因此後續模擬著重在LP40,1以下，即LP1,1、LP5,1、LP10,1、LP20,1、LP30,1、LP40,1。並且定義了四項側面泵浦耦合器的幾何參數，包括泵浦光纖末端進入雙披覆層光纖的融合深度(Df)、泵浦光纖拉椎長度(Ltp)、泵浦光纖末端最細的直徑(Dend)、融合起始點的泵浦光纖直徑(Dct)等。完成各組合之模擬結果，我們得到各模態之最佳化的耦合效率組合和有效折射係數組合，並且進一步提出如使用較大直徑的雙披覆層光纖，藉此能夠有效提升側面耦合器之耦合效率。

In this thesis, we discussed and simulated the coupling efficiency of the electromagnetic field of the side-coupled pump combiners and analyzed the influence of related geometric parameters on the final power coupling efficiency to optimize the component design.
The Beam propagation method (BPM, Rsoft BeamPROP software) is used for this simulation research. Before the simulation starts, we first adjust the initial linear-polarization mode order through the Rsoft simulation software and calculate the effective refractive index of the photon when the corresponding initial pump source enters the multimode fiber. Therefore, we can transmit the maximum mode order in the multimode fiber that we used is LP70,1. Next, in order to meet the specifications of the pump light source commonly used in our laboratory, the light source used is a laser diode (about 95% of the light source has a numerical aperture equal to 0.13). After using the formula to convert numerical aperture to the photon effective refractive index, the NA=0.13 mode order is close to LP40,1. The subsequent simulation will focus on the mode that lower than LP40,1, namely LP1,1, LP5,1, LP10,1, LP20,1, LP30,1, LP40,1.
We also define four geometric parameters of the side-coupled pump combiners, including the fusion depth (Df) of the pump fiber end into the double-clad fiber, the pump fiber taper length (Ltp), and the smallest diameter of the pump fiber end (Dend), the diameter of the pump fiber at the contacting point of the fusion (Dct).
After completing the simulation results of each combination, we obtained the optimal combination of coupling efficiency and effective refraction index for each mode order.
Furthermore, we proposed that if we used a larger diameter double-clad fiber, the coupling efficiency of the side-coupled combiner can be effectively improved.

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