入射光束的发散角会影响角度调谐窄带滤光片的透射特性，出现透射通带变小及发散损耗增大的情况，且该现象随着入射角度的增大而更加明显。分析了出现这些现象的原因，并根据拉赫不变量定理设计了扩束棱镜组来压缩入射光束的发散角。并利用二次滤波技术进一步提高了透射光谱的矩形度和稳定性。根据该方法设计了针对100 GHz密集波分复用系统角度调谐窄带滤光片的光学整形系统，实验结果表明，该方法能有效地改善入射光束发散角对器件滤波特性的影响。

The divergence angle of an incident beam will change the characteristics of a narrow-band angle-tuned thin-film filter whose passband will decrease and divergence loss will increase. This phenomena will be more and more obvious while the incident angle is increasing. Here its reason is analyzed. According to the Lagrange-Helmholtz principle, a beam expander is designed to compress the divergence angle of the incident beam. The double filtering technology is used to enhance the passband stability and the rectangle factor of the angle-tuned filter. One kind of shaping optic system is fabricated to the 100 GHz DWDM narrow-band angle-tuned filter. Experimental results show that the shaping system could effectively eliminate the influence of the divergence angle to the filter.