提出了基于束传输法（BPM）的大孔径光纤锥形过渡器理论分析模型。讨论了过渡器在纵向边界线性和非线性情况下（包括类似正弦型和余弦型变化），分别以大小端作为输入端口，耦合角度以及耦合长度对过渡器的损耗和耦合效率的影响，得出了过渡器最佳纵向边界、耦合角度和耦合长度。

An analytical model for the large-core optical fiber connector is presented based on beam propagation method(BPM). In the case of the linear and nonlinear (including sinusoidal and cosine) vertical section of connector, affections of the coupling length and coupling angle for the connector on the insert loss and coupling efficiency are discussed when the beginning section and the ending section act as the input respectively. Optimum vertical section, length, and angle of the connector are obtained.