提出一种利用饱和增益半导体光放大器(SOA)自增益调制效应抑制光电振荡器(OEO)相位噪声的方案。此方案将SOA置于光电振荡环路中,通过调节光衰减器及SOA的驱动电流使SOA工作在饱和增益状态,利用自增益调制效应抑制调制光信号的部分幅度噪声,提高环路的噪信比,从而降低产生微波信号的相位噪声。对OEO相位噪声的组成及SOA抑制幅度噪声的原理进行理论分析和实验验证,实验结果表明:在腔长为5 km的单环结构OEO中加入饱和工作状态的SOA,在0.1 kHz下产生的10 GHz微波信号近端相位噪声为-84.5 dBc/Hz,在1 kHz 下产生的相位噪声为-113.9 dBc/Hz,与未加入SOA的结构相比,相位噪声优化了3 dB,实验结果与理论分析基本一致。

This study proposes a method for suppressing phase noise of an optoelectronic oscillator (OEO) based on self-gain modulation effect of a gain-saturated semiconductor optical amplifier (SOA). The SOA is added into the OEO loop and operates in gain-saturated state by adjusting the optical attenuator and drive currents. Partial amplitude noise in modulated optical signal is suppressed due to the SOA's self-gain modulation effect, thereby improving the signal-to-noise ratio of the loop and reducing the phase noise of generated microwave signal. Furthermore, the composition of phase noise in the OEO and the noise-suppression principle of the SOA are analyzed and experimentally verified. The experimental results indicate that when we add a gain-saturated SOA in a 5-km-long single-loop OEO, the near-end phase noises of 10 GHz microwave signal are -84.5 dBc/Hz and -113.9 dBc/Hz under 0.1 kHz and 1 kHz, respectively, i.e., an improvement of 3 dB over that without the SOA. The experimental results are in agreement with the theoretical analysis.