提出了一种基于三芯光纤的模式复用器/解复用器, 三个纤芯包括两个相同的单模纤芯和一个少模纤芯, 在少模纤芯中写入长周期光纤光栅以实现单模纤芯中LP01模与少模纤芯中LP11模间的转换。同时从两个单模纤芯输入LP01模, 能激发少模纤芯中两个简并的LP11,a模和LP11,b模。采用光束传播法分析了该模式复用器/解复用器的耦合特性及串扰。数值模拟结果显示, 若以少模纤芯中LP11模输出能量大于-1dB的波长范围作为该模式复用器/解复用器的工作带宽, 则能够达到23nm, 并且少模纤芯中生成的其他模式的输出能量皆比LP11模的输出能量小-21dB以上。该模式复用器/解复用器能够实现对少模光纤的模式复用与解复用, 并具有极低的串扰。

A mode multi/demultiplexer based on a three-core optical fiber that three cores are two single-mode cores and a few-mode core is proposed. Apply a long-period fiber grating to realize mode conversion between LP01 mode in the single-mode core and LP11 mode in the few-mode core. Launched LP01 mode from two single-mode cores simultaneously, can stimulate two degenerate LP11,a mode and LP11,b mode. Analyze coupling characteristics and cross talk of the mode multi/demultiplexer using the beam propagation method. Numerical simulation shows that the operation bandwidth of the mode multi/demultiplexer can be 23nm if the normalized output power of LP11 mode in the few-mode core should be higher than -1dB, as well as the output powers of other modes all are lower -21dB above than that of LP11 mode in the few-mode core. The mode multi/demultiplexer can realize mode multiplexing and demultiplexing.