为了提高 Triplexer Monitor的光信号采样性能和集成度, 提出一种基于非对称锥形波导结构的波长不敏感耦合器。该耦合器采用 SiO2-on-Si掩埋型光波导结构, 位于中心部位的锥形波导构成耦合区, 与之衔接的 S型弯曲波导实现信号光的输入和输出。采用传输矩阵法分析了光监测端口输出的归一化的耦合光功率, 分析时将耦合区的中心部位作为非对称矩形波导而外侧作为对称矩形波导。利用光束有限差分传播法 (FDBPM)和 MATLAB数值仿真得出: 当耦合区中心非对称矩形波导宽度分别为 5.50 μm和 3.35 μm时, 对于 1 300 nm到 1 600 nm的输入光波长范围, 可实现光监测端口 4%～8%的归一化耦合光功率。特别的, 在 1 310 nm、1 490 nm和 1 550 nm输入光波条件下, 耦合器在输出端的分光比分别为: 92:8、96:4和 93:7, 同时 TE模和 TM模的分光比变化保持在 5%以内。所设计的波长不敏感耦合器具有体积小、可靠性高等优点, 适合与 PLC型的 Triplexer实现单片集成。

In order to improve performance of sampling optical signals as well as level of integration for Triplexer monitor, a wavelength-insensitive directional couple (WIDC) based on asymmetric-taper was presented. The WIDC adopted SiO2-on-Si buried type optical waveguide structure, with the taper waveguides constituting the coupling region at the center part and the S type bent waveguides used for the signal light into and output. The transfer matrix method was used to analyze the normalization of the coupling optical power at the light monitoring output port. The center region of WIDC was regarded as asymmetric rectangular waveguides and the lateral region was regarded as symmetric rectangular waveguides. Numerical simulations by both the Finite Difference Beam Propagation Method (FDBPM) and Matlab showed that when the input wavelengths varied from 1 300 nm to 1 600 nm, the normalized coupled optical power achieved by the WIDC was 4%～8%. In particular, the splitting ratios of WIDC were 92:8, 96:4 and 93:7 respectively when the input wavelengths were 1 310 nm, 1 490 nm and 1 550 nm correspondingly with the polarization variations less than 5% under the condition that maximum width and minimum width of the tapered waveguide were 5.50 μm and 3.35 μm respectively. The devised WIDC offers many advantages such as small size and high reliability and suitable for the Planar Lightwave Circuit (PLC)-based Triplexer.