基于光谱分析的强度调制器半波电压测量

为了提高信息容量,调制器的调制信号已经发展到Ka微波频段,频率往往大于10 GHz,带宽达到几十GHz.这使得其半波电压会发生明显的变化,进而直接影响到调制器的调制效率以及光谱特性.将光谱分析法推广到强度调制器半波电压的测量中,理论分析了MZM调制器(Mach-Zehder modulator,MZM)在射频(radio frequency,RF)信号调制下的输出光光谱特性,利用调制边带强度比计算调制器在不同的调制频率和调制功率下的半波电压.实验结果表明:MZM调制器半波电压随着输入射频频率的增加而上升,且与输入调制功率的变化相比,调制频率的变化对调制器半波电压的影响更大.针对不同调制条件下对强度调制器的半波电压进行测量,可为优化设计微波光子链路提供基础数据,对提高系统的传输性能具有重要实用意义.

Measurement Method for the Half-wave Voltage of Intensity Modulator Based on Spectrometer Method

To improve the information capacity, the modulation signal usually has the Ka-band (≥10 GHz) frequency and dozens of GHz bandwidth. The half-wave voltage of Mach-Zehder modulator ( MZM) will be obviously changed and the modulation efficiency and optical spectrum characteristic will be influenced. The half-wave voltage of the MZM was measured based on the spectrometer method. The spectral characteristic of the MZM was analyzed theoretically and the half-wave voltage of the MZM was calculated through the intensity ratio of modulation sideband. The half-wave voltages were measured experimentally when loading radio frequency ( RF ) signal with different frequencies and powers on the MZM. Results show that the half-wave voltage of the MZM increases with the increase of the modulation frequency. Furthermore, the changing of modulation frequency has large influence on the half-wave voltage than that of the modulation power. Measuring the half-wave voltage of the MZM with the different modulation conditions can support the optimization of the microwave photonic systems, and it is of significance to improve the performance of the systems.