Abstract:Aiming at the frequency response measurement problem of high-speed photodetectors (PDs), a self-calibrated electro-optical stimulus method is proposed for characterizing frequency responses of high-speed PDs based on dual-drive modulation. It eliminates the extra calibration for the uneven response of the electro-optic response devices and achieves self-calibrated characterization of the frequency response of high-speed PDs by keeping approximately equal dual-drive modulation frequency relationship. Moreover, the proposed method enables the frequency response of PDs by employing relative electrical power between sum-frequency and difference-frequency beat sidebands of dual-drive modulation frequencies so that it gets rid of bias drift from the dual-drive Mach-Zehnder modulator (DDMZM) and expands double measurement range. Compared to the all-optical stimulus method, the proposed method improves the measurement accuracy and dynamic range of frequency response of high-speed PDs. Different from the conventional electro-optical stimulus method, the method not only requires no extra calibration for electro-optic response devices, but also cancels out the influence from the bias of the intensity modulator and doubles measuring frequency range. Superior to the former two-tone modulation method, it simplifies the measuring system and reduces measurement cost. Frequency responses as a function of modulation frequency are experimentally measured for a commercial PD, and consistency compared with the measured results from the intensity noise method and the factory data of the employed PD fully verifies the accuracy of our method.