针对多腔窄带薄膜滤光片在倾斜入射时会产生严重的偏振相关损耗问题，研制了一种基于双折射晶体偏振分束器、信道间隔为100 GHz 的角度可调薄膜滤波器。该方法可简化倾斜入射时多腔窄带薄膜滤光片消偏振膜系结构，通过对入射光信号偏振态的控制，仅使用常规窄带滤光片就能实现角度调谐其中心透射波长。该可调谐滤波器件具有结构简单、成本低和偏振相关损耗小的特点，实验测试证明其可调谐波长范围可覆盖整个C 波段。

In oblique incidence, the multiple-cavity narrowband thin-film filter will have high polarization dependent loss. A novel 100 GHz angle-tuned thin-film filter with low polarization dependent loss based on the birefractance crystal polarization beam splitter is proposed. By modulating the incident angle and the polarization modes of the incident light, only the general thin-film filter can change its transmitting central wavelength. The stack of the multiple-cavity thin-film filter can be greatly simplified, and its cost will be reduced. This tunable filter has many advantages such as simple structure, low cost and low polarization dependent loss. The experiment shows that its tunable range can easily cover the whole C-band.