Self-Calibrating Microwave Characterization of Broadband Mach–Zehnder Electro-Optic Modulator Employing Low-Speed Photonic Down-Conversion Sampling and Low-Frequency Detection

An approach to characterizing the microwave performance of an electro-optic Mach–Zehnder modulator (MZM) is proposed based on photonic down-conversion sampling. Through low-speed sampling, the magnitude response of the MZM at the input microwave frequency is transferred to the duplicate component in the first Nyquist frequency range, and can be measured via low-frequency detection and spectrum analysis. A proof-of-concept experiment is carried out to demonstrate the feasibility of the proposed method, where magnitude-frequency response and half-wave voltage versus frequency of a commercial MZM in the frequency range of 0–40 GHz have been accurately measured under a sampling rate of 96.9 MS/s. Both simulation and experimental results indicate that the proposed method can be implemented without any extra calibration.