Low-speed photonic sampling for self-referenced frequency response characterization of high-speed photodetectors

An approach to measuring ultra-wideband frequency responses of high-speed photodetectors (PDs) is proposed based on low-speed photonic sampling. The optical frequency comb lines of a mode-locked laser diode (MLLD) can be used as the ultra-wideband and scalable optical stimulus of PD. The relative frequency response of PD can be extracted by analyzing the frequency components at comb lines of the MLLD. Thereinto, the uneven response of the MLLD can be eliminated through the specific frequency photonic sampling, thereby realizing the self-referenced and ultra-wideband measurement of PD. Moreover, the measuring frequency range is 2M-fold expanded with respect to the operating range of the microwave modulation frequency.