中国激光, 2020, 47 (6): 0601001, 网络出版: 2020-06-03
导频自适应的电光调制器激光脉冲调制技术 下载: 1189次
Dither-Adaptive Laser Pulse Modulation Technique for Electro-Optic Modulator
激光光学 激光脉冲 马赫-曾德尔调制器 消光比 数字信号处理器 laser optics lasers pulse Mach-Zehnder modulator extinction ratio digital signal processor
摘要
为解决脉冲信号对导频产生干扰进而导致马赫-曾德尔电光调制器(MZM)工作点无法稳定的问题,提出了一种导频自适应的偏压控制技术。采用数字控制系统生成频率可变的导频,由快速傅里叶变换分析反馈信号的谐波分量,可以将MZM锁定于传输曲线的最低偏置点。通过实时监测偏置电压输出,自主改变导频频率,避免脉冲信号对导频的影响,实现了高消光比的激光脉冲调制。结果表明,激光脉冲的重复频率与导频一次谐波频率接近时,脉冲信号会影响调制器工作点的稳定,该系统可以实现导频频率在0.45~2 kHz范围内的自适应变化,满足不同重复频率的激光脉冲调制需求。脉冲峰值为10 V、占空比为10 %时,调制光脉冲的消光比可达26 dB,相较于脉冲信号对导频产生干扰时,输出脉冲消光比提高了约24 dB。
Abstract
In this study, to solve the problem of interference of the pulse signal with the dither, which makes the Mach-Zehnder electro-optic modulator (MZM) operating point unstable, a dither-adaptive bias-control technique is proposed. A digital control system was used to generate a dither with variable frequency. The MZM can be locked at the minimum operating point of the transmission curve by the harmonic components of the feedback signal analyzed by fast Fourier transform. By the real-time monitoring of the output bias voltage, the dither frequency is able to automatically change, thus avoiding the influence of the pulse signal. Accordingly, laser pulse modulation with high extinction ratio is realized. Experiment results show that the pulse signal will affect the stability of the modulator operating point when the laser pulse frequency is close to the first harmonic frequency of the dither. The system can realize adaptive change of the dither frequency in the range of 0.45--2 kHz to meet the requirements of laser pulse modulation at different repetition frequencies. When the peak value of the pulse is 10 V and the duty cycle is 10%, the extinction ratio of the modulated optical pulse can reach 26 dB, which is approximately 24 dB higher than that when the pulse signal interferes with the dither.
周鹏威, 卢田, 吕晋阳. 导频自适应的电光调制器激光脉冲调制技术[J]. 中国激光, 2020, 47(6): 0601001. Zhou Pengwei, Lu Tian, Lü Jinyang. Dither-Adaptive Laser Pulse Modulation Technique for Electro-Optic Modulator[J]. Chinese Journal of Lasers, 2020, 47(6): 0601001.