Equal-phase resampling with periodic error suppression in swept-source interferometry under non-ideal I/Q demodulation

Equal-phase resampling is a key technique for compensating laser sweep nonlinearity in swept-source interferometry. Phase extraction based on optical I/Q demodulation avoids complex global computations, offering a highly promising approach for low-latency resampling. However, practical wideband 90 ∘ hybrids inevitably suffer from amplitude mismatch and quadrature phase deviation. Such non-ideal I/Q demodulation introduces a phase-dependent ripple that severely perturbs the resampling grid, elevates spurs/sidelobes, and degrades spectral focusing. In this paper, we propose an equal-phase resampling method named PESR (Periodic Error Suppressed Resampling), which remains highly reliable even under severe I/Q imbalance (including hardware band mismatch). Without relying on conventional small-signal approximations, we theoretically prove that the arctangent demodulation error induced by quadrature errors has an intrinsic π -periodic component in the phase domain. Exploiting this property, we propose a “residual-phase-error filtering” strategy that effectively suppresses the periodic ripple while perfectly preserving the slow-varying phase trend dictating the resampling scale. Simulations not only verify this π -periodic characteristic but also reveal why directly applying a low-pass filter to the total phase introduces resampling scale bias. Experiments on a swept-source interferometric ranging platform demonstrate that, under massive quadrature errors, PESR suppresses the sidelobes of the single-sweep spectrum to approximately −25.5 dBc; in point-ranging evaluations, it achieves a sub-3- µ m RMS accuracy and an ultra-high measurement repeatability (MeanSTD) of 0.09~ µ m. Furthermore, PESR relaxes the reliance of traditional methods on a long auxiliary optical path difference, providing a robust and efficient solution for practical sweep nonlinearity correction and high-stability metrology.