基于轨道角动量的多端口大容量密度光交换关键技术研究

The dramatic increase of telecommunication demand puts new challenges on the network resource allocation and the control technologies, especially for the high efficiently switching technology supporting the spacial division multiplexing and elastic optical networks. Because of the indistinguishability of the overlapping regular beams, the existing optical switching technologies have to separate the beams before steer them and thus cannot support large port density and have poor port extension ability. In view these problems, based on our previous work, this project for the first time proposes a radically new optical switching mechanism, using the orthogonality and distinguishability of orbital angular momentum (OAM) beam to over the above problem. It makes the overlapped beams can be separated and steered to different output ports. The main contents of this project includes: 1. Solving the problem of relationship between the phase structure of OAM beams and the direction of the output optical transformation beams, and designing a device to realize the high efficient transformation from multiple Gaussian beams to coaxial multiple OAM beams. 2. Modeling the relationship of the holograph grating’ structure and the demultiplex direction of OAM beams, and designing novel OAM gratings to realize the high efficiently, flexibly demultiplex routing of the multiple coaxial OAM beams. 3. Setting up the multi -input multi-output optical switching experiment system, evaluating and optimizing the optical switching performance through the signal to noise ratio and bit error rate testing to realize the flexibly switching of the multiport optical signal with high port density. The objective for this project is to realize N×N (N≥16) ports optical switch with single path transmission rate up to Tbit/s. This project will develop the large capacity, multiport and flexible optical switching technology, to promote the development of the optical network technologies.

通信需求急速增长对网络资源管控技术提出新挑战，尤其是下一代结合空分复用的大容量弹性光网络中的高效交换技术。针对现有光交换技术缺乏区分交叠光信道能力而导致的交换端口密度低、扩展能力差等问题，本项目在前期工作基础上，首次提出利用轨道角动量(OAM)光束的正交性和其拓扑荷差异性来区分交叠的光载波信道，解决常规光交换中各路光不能平行交叠问题。研究内容包括：1.解决OAM光束相位结构与光学变换空间输出方向的关联问题，设计器件实现多路同轴OAM光束的同时高效转化；2.建立全息光栅与OAM光束解调输出方向的关系模型，设计新型OAM光栅实现多路OAM光同时、高效、灵活解调路由；3. 搭建实验系统，研究交换性能并进行系统再优化，实现端口密度高的多端口灵活光交换。预期通过本课题研究，最终实现单路容量达Tb级的N×N光交换(N不小于16)，为大容量、多端口灵活光交换技术提供新的解决方案，促进光网络技术的发展。

当下面对单模光纤通信网络络的容量瓶颈，空分复用传输技术已经走向工程化研究阶段，而提升空分复用光通信网络的频谱资源利用率，在大绝对通信带宽资源的基础上进行有效带宽资源管控调配能力，提升整个网络的承载能力和效率是一个急需解决的问题。面对空分光交换中无法区分控制交叠光束的问题，本项目以发展实现一种自由空间光线路交换为核心的自由空间光交换技术、解决未来空分光网络的交换问题为目标，运用光学模式的轨道角动量在作为空间交叠模式的区分操纵参量标签，通过空间光场模式变换进行轨道角动量的标签加载，运用标签解复用的空间变换驱动实现信道模式的空间切换，从而解决光交换中交叠光的区分操纵问题。.在高效率低损耗的多路轨道角动量标签加载方面，通过经过预处理的几何变换和宽谱的多平面变换两种方案的优化，分别实现了6路插损低于1.6dB的C+L波段的复用标签（拓扑荷标签可-10到+10中间任意选择加载）和16路损耗低于3dB的高隔离度的C+L波段的复用标签。在去标签解复用降低串扰和拓展解复用路数方面，通过径向相位调控和基于光线追迹的几何变换相位畸变的补偿技术，实现了标签解复用后的模式分布空间的二维拓展和解复用拓扑荷数空间到正负16的拓展。在标签操纵模式切换方面，通过级联相移光栅的方案和构造在线模式干涉仪的方法，提出了多阶模式标签的任意切换和多波长模式标签同时切换的方法，并实验上正是了方案的有效性，高低阶模式的切换效率高于95%, 实验演示的波长数达到17个。.实验结果证实了基于轨道角动量标签的光交换可解决空间交叠光束无法区分操控的问题，对实现超大容量光交换体系在空间维度的高密度实现提供了佐证和实现思路，具有非常强的科学意义和应用价值。项目支持或部分支持申请发明专利8项、授权3项、实审5项，公开发表学术论文16篇、其中top级论文12篇