马赫-曾德尔电光调制器产生等幅光频梳的工作点控制研究

Study of Operating Points Control for MZ Electro-Optic Moudulator in Generating Equal-Amplitude Optical Frequency Comb

提出一种利用马赫曾德尔（MZ）电光调制器（EOM）产生多波长光源的方案。深入分析了EOM在单频微波信号调制下的扩频特性，仿真了其频域产生光边带的情况，得出在调制度C=1.84时可实现等频率间隔、边模抑制比（SMSR）为15 dB的五阶等幅光频梳（OFC）输出的结论。并提出一种基于虚拟仪器及微扰谐波响应的闭环反馈工作点控制方案，可自动锁定EOM的工作点于传输曲线上任意点。应用该控制方案实现了稳定的五阶等幅光频梳输出，1 h内输出功率的漂移小于其平均值的0.3%，光频梳平坦度小于0.4 dB，中心五阶光边带功率起伏的标准差小于0.15 dB/h。

A method is proposed based on Mach-Zehnder （MZ） electro-optic modulator （EOM） to generate multi-wavelength laser. An exhaustive analysis about the spectrum broadening characteristic of EOMs is proposed and the generation of optical sidebands is simulated. A conclusion is made that five-order equal-amplitude sidebands with a side mode suppression ratio （SMSR） of 15 dB can be achieved when modulation index C=1.84. Also a practical operating points control method is proposed based on virtual instrument technique and harmonic response of dither signal in a closed loop feedback system for EOM, which can realize EOM arbitrary operating points automatic control. In the experiment, the EOM output power drift is less than 0.3% and sidebands flatness is 0.4 dB in an hour. The power standard deviation of center five order sidebands is 0.15 dB/h.