Complete model identification for measuring photodetector’s data age in high-speed and high-precision interferometry

Data age in photodetectors is a key indicator in high-speed and high-precision interferometry. Accurately measuring it is essential for ensuring timely control of high-speed movement and synchronization in dynamic calibration. Current methods for measuring photoelectric data age are limited by their inability to simultaneously account for phase shifts and time delays, primarily due to incomplete models. This study introduces a complete model identification method that integrates nonlinear phase and fixed delay, providing a more accurate measurement of the photodetector's data age. By analyzing laser impulse response sequences with Hankel matrix and phase spectrum, the proposed method achieves 95% model reliability and a measurement uncertainty of 51 ps (k = 2) for a photodetector with 400 MHz bandwidth. This work has significant potential to compensate for non-real-time and nonlinear errors in interferometry.