Scalable High-frequency Measurement of Photodetectors through Harmonic Up-conversion Based on Pilot-aided Electro-optical Stimulus

A scalable electrical method is proposed for measuring high-frequency responses of photodetectors (PDs) through harmonic up-conversion based on pilot-aided electro-optical stimulus. The proposed method provides wideband optical stimulus by the electro-optical harmonic up-conversion and subtracts the frequency response of the assisted electro-optical Mach-Zehnder modulator (MZM) based on the pilot insertion and extraction fixed at low frequency, which is free of any golden intensity modulator (IM) of known performance. Moreover, it achieves wideband and scalable high-frequency measurement of PDs with n-fold measuring frequency range, where the sweeping frequency up to fs of the assisted MZM enables the measuring frequency range of n×fs. In the experimental demonstration, a commercial PD is measured with an assisted MZM under a frequency-swept modulation up to 16.75 GHz and a fixed-low-frequency pilot signal at 80 MHz, and the frequency responses are evaluated up to 67 GHz. Moreover, the feasibility of the scalable scheme is proved by those cases of 1, 2, 3, and 4-fold measuring frequency range. The consistency between our method and the two-tone mixing method verifies that the scalable high-frequency measurement provides a simple but accurate method for the performance characterization of high-speed PDs.