The chirp parameter of a silicon optical modulator (SOM) is difficult to measure precisely because the plasma dispersion effect is due to electro-refraction and electro-absorption occurring simultaneously. A novel method for measuring the chirp parameter of a SOM is presented, which is adopted from the beat-frequency method. Firstly, based on the model of the differential driver silicon Mach–Zehnder modulator(DDSMZM), the chirp parameter of the DDSMZM is presented by mathematical derivations, and we prove that achieving the multi-order coefficients of the radio frequency phase shift is a key point for characterizing the chirp accurately. In the proposed method, a wavelength tunable laser, as a local source, is applied to mix with the chirped modulated optical signal of the DDSMZM. In this way, the multi-order electric signals of beat frequency are mapped from high-frequency to low-frequency. Meanwhile, a balanced detector with a low-speed trans-impedance amplifier(TIA) is employed for realizing photo-electric conversion, which can improve the signal-to-noise ratio of the measurement. Finally, we have examined the chirp parameter of the DDSMZM in the case of low-frequency and high-frequency modulation signal condition and the results show the beat-frequency method has a higher frequency resolution and measurement accuracy for measuring the chirp parameter of the DDSMZM compared with the optical spectrum analysis(OSA) method and the optical heterodyne method.

中文翻译：

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测量硅马赫-曾德调制器啁啾的高阶电谱法

硅光调制器 (SOM) 的啁啾参数难以精确测量，因为等离子体色散效应是由于电折射和电吸收同时发生。提出了一种测量 SOM 线性调频脉冲参数的新方法，该方法采用拍频方法。首先，基于差分驱动硅马赫-曾德调制器（DDSMZM）的模型，通过数学推导给出了DDSMZM的chirp参数，证明了实现射频相移的多阶系数是关键准确表征啁啾的点。在所提出的方法中，波长可调谐激光器作为本地源，用于与 DDSMZM 的啁啾调制光信号混合。这样，拍频的多阶电信号从高频映射到低频。同时，采用带低速跨阻放大器（TIA）的平衡检测器实现光电转换，可提高测量的信噪比。最后，我们考察了低频和高频调制信号条件下DDSMZM的chirp参数，结果表明拍频法测量DDSMZM的chirp参数具有更高的频率分辨率和测量精度。与光谱分析（OSA）法和光外差法相比。可以提高测量的信噪比。最后，我们考察了低频和高频调制信号条件下DDSMZM的chirp参数，结果表明拍频法测量DDSMZM的chirp参数具有更高的频率分辨率和测量精度。与光谱分析（OSA）法和光外差法相比。可以提高测量的信噪比。最后，我们考察了低频和高频调制信号条件下DDSMZM的chirp参数，结果表明拍频法测量DDSMZM的chirp参数具有更高的频率分辨率和测量精度。与光谱分析（OSA）法和光外差法相比。