Microwave Frequency-to-Phase-Slope-Ratio Mapping via Photonic Polarization-Division Multiplexing of Time-Varying Delay

Microwave photonic frequency-to-phase-slope mapping (FTPSM) is susceptible to frequency measurement errors, primarily induced by delay-rate uncertainty and fluctuations. To address this limitation, we propose a novel frequency-to-phase-slope-ratio mapping (FTPSRM) method that incorporates a reference signal sharing the same time-varying delay path as the signal under test (SUT). By leveraging the phase-slope ratio, this approach eliminates the need for delay-rate calibration while mitigating the impact of delay-rate fluctuations on measurement accuracy. The FTPSRM is implemented in a microwave photonic system utilizing polarization-division multiplexing of time-varying delay. The experimental results demonstrate that the FTPSRM reduces the maximum frequency error from 602 to 234 MHz and the standard deviation from 743 to 301 MHz across the 1–10-GHz range, significantly improving both accuracy and stability under delay fluctuations.