Frequency-Swept Interferometric Clearance Measurement Based on Microwave Photonic Dual-Sideband Modulation

To eliminate the sensitivity of frequency-swept interferometric ranging to Doppler-induced errors and laser frequency-sweeping nonlinearities, as well as to overcome the limitations of existing suppression strategies—such as strict synchronization requirements in dual-sweep configurations and increased system complexity in single-sweep schemes with auxiliary optical paths—a microwave photonic frequency-swept interferometric method based on dual-sideband modulation is proposed. In the proposed approach, an electro-optic modulator is utilized to generate a pair of frequency-symmetric optical sidebands with opposite chirp characteristics. Owing to the bidirectional symmetry of the frequency sweeps, Doppler-induced and frequency-sweeping nonlinearity induced errors in the two sidebands exhibit equal magnitudes but opposite signs, enabling intrinsic cancellation of Doppler effects as well as compensation of system-nonlinearity induced errors. Experimental validation demonstrates that, compared with conventional frequency-swept interferometric techniques, the proposed method achieves approximately 35% improvement in measurement accuracy under dynamic conditions, while preserving high resolution and strong robustness against environmental perturbations. The results indicate that the proposed scheme offers a simple, effective, and practical solution for high-precision dynamic ranging in high-speed and complex environments.