Wavelength-division multiplexed optical communication systems used in 5G networks require tunable wavelength filters with narrow bandwidth for 100 GHz channel spacing, wide wavelength range to cover 16 channels, and a side mode suppression ratio (SMSR) exceeding 30 dB. To fabricate wavelength filters satisfying these specifications, tunable Bragg grating filters based on polymeric optical waveguides are proposed. The combination of mode-sorting waveguide and tilted Bragg grating enables the extraction of Bragg reflected signals to another path, without using an external circulator. Moreover, the double reflection by the two-stage cascaded structure produces narrower reflection bandwidth, improved SMSR characteristics, and reduced adjacent-channel crosstalk through the suppression of undesired mode coupling. The proposed device exhibits a 20 dB bandwidth of 1.0 nm and SMSR of 35 dB, over the entire wavelength-tuning range.

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具有两级级联倾斜布拉格光栅的聚合物可调波长滤光片

5G网络中使用的波分复用光通信系统需要波长范围为100 GHz的带宽可调的可调谐波长滤波器，覆盖16个信道的宽波长范围以及超过30 dB的边模抑制比（SMSR）。为了制造满足这些规格的波长滤波器，提出了基于聚合物光波导的可调布拉格光栅滤波器。模式分类波导和倾斜的布拉格光栅的组合使布拉格反射信号可以提取到另一条路径，而无需使用外部循环器。此外，通过抑制不希望的模式耦合，两级级联结构的双重反射产生更窄的反射带宽，改善的SMSR特性以及减少的相邻信道串扰。