Self-referenced frequency response measurement of high-speed photodetectors through segmental up-conversion based on low-speed photonic sampling

A self-referenced electrical method is proposed for measuring the frequency responses of high-speed photodetectors (PDs) through segmental up-conversion based on low-speed photonic sampling. The proposed method provides a very narrow linewidth and ultra-wideband optical stimulus by the segmental electro-optic up-conversion, and eliminates the uneven responses of mode-locked laser diode (MLLD) and electro-optic modulator (MOD) based on the symmetric frequency photonic sampling, which is free of any extra calibration. Moreover, it achieves ultra-wide and scalable frequency response measurement of PDs with 2M-fold measuring frequency range, where the symmetric sweeping frequency up to Nfr/2 of MOD enables the measuring frequency range of M × N×fr. For a proof-of-concept, two commercial PDs are measured with a sampling rate of 96.9 MS/s and a symmetric frequency-swept modulation up to 1.4575 GHz and 2.475 GHz, and their frequency responses are evaluated up to 29.07 GHz (=10 × 30 × fr) and 49.419 GHz (=10 × 51 × fr), respectively. The consistency between our method and conventional methods verifies that the scalable self-referenced measurement provides a simple but accurate method for the performance characterization of high-speed PDs.