Wu Xiaowen, Gao Shecheng, Tu Jiajing, Shen Lei, Hao Chenglong, Zhang Bin, Feng Yuanhua, Zhou Ji, Chen Shuner, Liu Weiping, Li Zhaohui
Opt Express. 2020 Nov 23;28(24):36084-36094. doi: 10.1364/OE.410202.
Mode division multiplexing has attracted great attention because it can potentially overcome the limitation of single-mode fiber traffic capacity. However, it has been challenging to realize multiple modes controlling and switching due to the intrinsic overlap of the modes in the transmission waveguide. As a solution, we propose a cascaded phase-shifted long-period fiber grating (PS-LPFG) based multiple mode switching scheme. Using the PS-LPFGs, the multiple guided orbital angular momentum (OAM) modes selective controlling and switching at multi-wavelength can be achieved in few-mode fibers by regulating the grating resonance condition. In principle, a N × N mode switch matrix can be realized by cascading 2 gratings, where each grating acts as a mode switch element to achieve a couple selected OAM mode switching and meanwhile the other modes are under nonblocking status. As a proof of the concept, a 2 × 2 mode switching between two OAM modes at different wavelengths based on one PS-LPFG element is demonstrated in our experiments. The switching efficiency of the two modes at two wavelengths 1537nm and 1558nm are ∼98.4% and ∼98.7%, respectively. The proposed multiple OAM mode switch has potential applications in the future hybrid multi-dimensional multiplexing optical fiber communication systems.
模式分割复用因其有望克服单模光纤通信容量的限制而备受关注。然而，由于传输波导中模式的固有重叠，实现多模式控制和切换一直具有挑战性。作为一种解决方案，我们提出了一种基于级联相移长周期光纤光栅（PS-LPFG）的多模式切换方案。利用PS-LPFG，可以通过调节光栅共振条件，在少模光纤中实现多波长下多个导模轨道角动量（OAM）模式的选择性控制和切换。原则上，通过级联两个光栅可以实现一个N×N模式开关矩阵，其中每个光栅作为一个模式开关元件，实现一对选定的OAM模式切换，同时其他模式处于非阻塞状态。作为概念验证，我们在实验中展示了基于一个PS-LPFG元件在不同波长下两个OAM模式之间的2×2模式切换。在1537nm和1558nm两个波长下，两种模式的切换效率分别约为98.4%和约98.7%。所提出的多OAM模式开关在未来的混合多维复用光纤通信系统中具有潜在应用。
