Frequency response measurement of Mach-Zehnder modulators utilizing double carrier based on low frequency detection

A frequency-shifted dual-carrier method is proposed for microwave characterization of Mach-Zehnder modulators based on low frequency detection. The proposed method utilizes the heterodyne products between the beats of two modulated sidebands, and achieves calibration-free microwave measurement of Mach-Zehnder modulators with the help of electrical spectrum analysis. Our method features low-frequency detection with only one microwave source and avoids the responsivity correction introduced by the photodetector. In the experiment, the frequency response of a Mach-Zehnder electro-optic intensity modulator is measured by using the proposed method, where the measurement results fit in with those obtained by using the conventional optical spectrum analysis method.