全光纤上下话路滤波器是光纤通信系统中的重要器件。光纤布拉格辅助失配耦合器型上下话路滤波器是非干涉型的,易于制作,并且稳定。采用波长为248 nm的紫外光在由标准单模光纤和自制的高掺锗光敏光纤熔融拉锥制作的2×2光纤耦合器上写入光纤光栅,实现了全光纤多端口上下话路滤波器。实验中获得了最大反射率约为20 dB,带宽约为2 nm的上下话路滤波器。实验分析表明在耦合器耦合区的均匀部分写入一定长度的啁啾布拉格光栅,或在耦合区的不均匀部分写入一定长度的均匀布拉格光栅,均可获得峰值反射率较高和带宽较大的光纤布拉格辅助失配耦合器型上下话路滤波器。

All-fiber add/drop filters are the key components in fiber communication systems. The Bragg grating assisted mismatched coupler for add/drop filter is not interferometric,easy to fabricate and works stable. The filter is based on 248 nm ultraviolet-written Bragg grating in 2×2 coupler fused with a standard single mode fiber and a self-made high germanium doped photosensitive fiber. The filter with maximum reflectivity about 20 dB,bandwidth about 2 nm is obtained. Filters with big maximum reflectivity and long bandwidth can be obtained by writing chirped Bragg grating on the uniform region of the coupler or writing Bragg grating on the non-uniform region of the coupler.