Multiplexing and demultiplexing of optical orbital angular momentum (OAM) are critical operations in mode-division multiplexing communications. Traditional Dammann gratings, spiral phase planes, and optical geometric transformations are regarded as convenient methods for OAM mode (de)multiplexing. However, crosstalk between the different modes and the difficulty of mode multiplexing greatly limit their application to mode-division multiplexing communications. Here, using a set of inversely-designed phase planes, we demonstrate an OAM (de)multiplexer based on multiphase plane light conversion that can enable perfect OAM multiplexing communication. The sorted patterns are Gaussian-like and can be coupled easily into single-mode fiber arrays. Inputs from the fiber array are turned into coaxial OAM modes after the phase planes. OAM mode crosstalk generated by the multiplexer is less than −20 dB$-20\mathrm{dB}$, with insertion loss of less than 2.6 dB. OAM modes are sorted by the demultiplexer with mode crosstalk below −10 dB$-10\mathrm{dB}$, and the sorting results are coupled to the fiber array. OAM modes carrying 10 Gbit/s on–off keying signals were transmitted in a 5 km few-mode fiber. The measured bit-error-rate curves have power penalties of less than 10 dB. The proposed configuration is highly efficient and convenient and will be beneficial for potential applications in quantum information, information processing, and optical communications.

中文翻译：

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通过逆向设计的多相平面光转换实现光学轨道角动量复用通信

光学轨道角动量 (OAM) 的复用和解复用是模分复用通信中的关键操作。传统的达曼光栅、螺旋相平面和光学几何变换被认为是 OAM 模式（解）复用的便捷方法。然而，不同模式之间的串扰和模式复用的难度极大地限制了它们在模分复用通信中的应用。在这里，我们使用一组反向设计的相平面，展示了一种基于多相平面光转换的 OAM（解）复用器，可以实现完美的 OAM 复用通信。排序后的图案类似于高斯，可以很容易地耦合到单模光纤阵列中。来自光纤阵列的输入在相平面之后变成同轴 OAM 模式。− 20 dB $-20\mathrm{dB}$，插入损耗小于 2.6 dB。OAM 模式由解复用器分类，模式串扰低于− 10 dB $-10\mathrm{dB}$，分类结果耦合到光纤阵列。承载 10 Gbit/s 开关键控信号的 OAM 模式在 5 km 少模光纤中传输。测得的误码率曲线的功率损失小于 10 dB。所提出的配置高效便捷，将有利于在量子信息、信息处理和光通信领域的潜在应用。