在SFP（小型可插拔）光模块中，LDD（激光器驱动器）是一个非常关键的部分，LDD调制端的电压余量是否足够关系到光模块能否正常工作及工作指标是否满足要求。文章分别讨论了VCSEL（垂直腔表面发射激光器）与LDD的直流和交流耦合对LDD调制端电压余量的影响。实验结果表明，采用交流耦合的接口方式可以有效地避免LDD调制端电压余量不足的情况出现，研究结果对使用VCSEL的SFP光模块的设计具有参考价值。

Laser Diode Driver (LDD) is a critical part of Small Form factor Pluggable (SFP) optical modules. The voltage margin sufficiency of LDD modulator determines if optical modules can work normally and their performances satisfy the requirements. This paper studies the influences of DC and AC coupling modes between VCSEL and LDD on the voltage margin of LDD modulator. The experimental results indicate that when AC-coupling mode is adopted, voltage margin insufficiency can be effectively avoided. This result is valuable for the design of SFP optical modules using VCSEL.