提出了一种基于环形芯铒离子部分掺杂光纤的涡旋光纤放大器。针对该掺铒光纤的放大特性, 研究了光纤长度、掺铒浓度与抽运功率对信号模式增益特性的影响。研究结果表明, 该光纤放大器能够支持22个轨道角动量模式稳定传输, 且C波段(1 530～1 565 nm)所有信号模式增益大于23 dB, 信噪比高于27 dB, 差分模式增益小于0.015 dB。所提出的基于环形芯光纤的涡旋光纤放大器具有支持轨道角动量模式数量多、差分模式增益低、信噪比高的优势, 对于OAM复用长距离传输系统中的在线放大具有重要参考价值。

A vortex fiber amplifier is proposed, which is based on a ring core fiber with erbium ions doped partially in the ring core areas. For the amplification characteristics of the erbium-doped fiber, the effects of fiber length, erbium-doped concentration and pump power on the gain characteristics of the signal modes are studied. The results show that the proposed fiber amplifier can support 22 orbital angular momentum (OAM) modes transmit stably. Meanwhile, the gain of all signal modes is larger than 23 dB, the signal-to-noise ratio is larger than 27 dB, and the differential mode gain (DMG) is less than 0.015 dB at C band (1 530-1 565 nm). The proposed vortex fiber amplifier based on the ring core fiber has the advantages of supporting large number of orbital angular momentum modes, low differential mode gain and high signal-to-noise ratio, which has important value for online amplification in an OAM-multiplex transmission system with long distance.