超大规模高性能 OAM 空分、模分复用光放大器数据

近年来通信速率的需求日益剧增，作为传输链路的单模光纤通信系统正在面临严峻的容量危机，亟需发展新的技术来应对。携带不同扑荷、相互正交的轨道角动量（Orbital Angular Momentum，OAM）模式，其复用可作为空分复用（Space Division Multiplexing，SDM）技术的新型实现方式，被寄予突破目前光纤通信系统容量瓶颈的厚望。为使 OAM 模式复用光纤通信系统实现长距离传输，高性能的在线型 OAM 掺铒光纤放大器（Erbium Doped Fiber Amplifier，OAM-EDFA）是必不可少的。多模式 OAM 掺铒光纤毫无疑问是 OAM-EDFA 的核心部件，在对 OAM 掺铒光纤进行增益均衡之后，还要以其为核心组建成接入并应用在光纤通信系统中的 OAM-EDFA，才能发挥 OAM-EDFA 推动长距离 OAM 模式复用传输系统实际应用的潜力。OAM模式用于光纤通信系统也有大量的报道，为了实现光纤通信系统的中的OAM模式的复用并且进行长距离的传输，研究高性能涡旋光纤放大器对OAM模式传输有着重要的意义。
本课题提出基于环形芯光纤的涡旋光纤放大器的设计方案，理论可实现超低模式增益；对方案所涉及的OAM掺铒增益光纤的制备进行了系列的研究，成功制备出了波导结构、掺杂浓度满足设计的OAM掺铒增益光纤。系统的研究了OAM掺铒光纤的预制棒制备工艺和光纤的拉制工艺，解决了OAM掺铒光纤制备研究过程中的诸多问题，实现了OAM掺铒光纤的成功制备，并在此基础上搭建了有源光纤的性能测试平台，通过空间的光路的形式对多模式的有源光纤进行性能测试。确定可靠的OAM模式复用增益测试方法；成功设计拉制出达到项目要求的单环芯EDF并实现5模组20模式低增益差放大；设计并研制出7环芯EDF，实现了4（模组）× 4（模式）×7（芯）=112模式均不低于20dB的增益。

In recent years, the demand for communication rates has grown exponentially, and single-mode fiber communication systems serving as transmission links are facing a severe capacity crisis, urgently requiring new technologies to address this challenge. Orbital Angular Momentum (OAM) modes carrying different topological charges and mutually orthogonal can be multiplexed as a novel implementation of Space Division Multiplexing (SDM) technology, which is highly anticipated to break through the current capacity bottleneck of fiber communication systems. To enable long-distance transmission of OAM mode multiplexed fiber communication systems, high-performance in-line OAM Erbium Doped Fiber Amplifiers (OAM-EDFA) are indispensable.

Undoubtedly, multi-mode OAM Erbium Doped Fibers are the core component of OAM-EDFA. Only after gain equalization is performed on OAM Erbium Doped Fibers and OAM-EDFAs are integrated into fiber communication systems with such fibers as the core can the potential of OAM-EDFA to promote the practical application of long-distance OAM mode multiplexed transmission systems be fully exerted.

There have been numerous reports on the application of OAM modes in fiber communication systems. To realize OAM mode multiplexing and long-distance transmission in fiber communication systems, researching high-performance vortex fiber amplifiers holds great significance for OAM mode transmission.

This study proposes a design scheme for a vortex fiber amplifier based on ring-core fibers, which can theoretically achieve ultra-low mode gain differences. A series of studies were conducted on the preparation of OAM Erbium Doped Gain Fibers involved in this scheme, and OAM Erbium Doped Gain Fibers with waveguide structures and doping concentrations meeting the design requirements were successfully fabricated. Systematic studies were carried out on the preform fabrication process and fiber drawing process of OAM Erbium Doped Fibers. Various problems encountered during the preparation and research of OAM Erbium Doped Fibers were resolved, and the successful fabrication of OAM Erbium Doped Fibers was achieved. On this basis, a performance test platform for active fibers was established, and the performance of multi-mode active fibers was tested via spatial optical paths.

A reliable test method for OAM mode multiplexing gain was established. Single-ring-core EDFs meeting the project requirements were successfully designed and drawn, and low-gain-difference amplification for 5 groups × 20 modes was realized. A 7-ring-core EDF was designed and developed, achieving a gain of no less than 20 dB for 112 modes (4 groups × 4 modes × 7 cores).