和直波导的不同在于 ,三维楔脊形波导中的光场都是不稳定的 .分别对波导_光纤耦合、光纤_波导耦合两种情况 ,将三维楔脊形波导等效为多段短的直波导 ,利用束传播法同时对三维楔脊形波导内不稳定的入射、反射场 ,及它们在传播方向上的偏导进行处理 ,再用自由空间辐射模法计算透射率和反射率 .以SOI楔脊形波导和光纤的耦合为例 ,验证了该方法的可行性 The difference between a waveguide and a straight waveguide is that the optical field in the three-dimensional wedged rib waveguide is unstable, and the three-dimensional wedge ridge waveguide is equivalent to a multi-segment and short straight Waveguide, the beam propagation method is used to process the unstable incidence and reflection fields in the three-dimensional wedge ridge waveguide and their partial derivatives in the propagation direction, and then the free space radiation mode is used to calculate the transmittance and reflectivity. The coupling between wedge ridge waveguide and optical fiber is taken as an example to verify the feasibility of this method