在1×N波分复用/解复用器中,N+1个自聚焦棒透镜构成了一个1到N的准直系统。自聚焦棒透镜之间的间隔不等,导致了较大的不均匀的附加耦合损耗。为了使总的平均损耗最低,N+1个自聚焦棒透镜的长度应匹配选择。数值计算结果表明,输入自聚焦棒透镜应比1/4节距稍长ΔZ0=20～50μm,因N而异,有一上限。N个输出自聚焦棒透镜的长度不等,靠近输入端者比1/4节距略短,远端者比1/4节距略长,亦因N而异。这样匹配使得总的损耗最低,适用于N≤8(尤其是N≤6)的情形。

There are N+1 gradient-index-rod lenses (GRINs) in a 1×N wavelength division multi/demultiplexer, forming a 1-to-N collimating system. Excess coupling losses arise due to the varying separations between the GRINs. The lengths of the GRINs need to be properly chosen to achieve a lowest average coupling loss. Numerical results show that the input GRIN is ΔZ0 longer than quarter pitch with ΔZ0=20～50 μm, depending on N. There is an upper limit for ΔZ0. The lengths of N output GRINs are differently shorter (ΔZi<0) or longer (>0) than quarter pitch. ΔZi increases from negative to positive starting from the near end to the far end GRINs, also depending upon N. The optimized matching GRINs assure the lowest coupling loss at N≤8, especially negligible at N≤6.