Broadband phase-noise suppression in fiber interferometers using specialty hollow-core photonic bandgap fibers

Fiber interferometers are widely used in precision measurements, yet phase-noise suppression over the mHz-kHz band remains a key bottleneck. Here, a specialty hollow-core photonic bandgap fiber (HC-PBGF) is introduced as the sensing arm to reduce temperature-induced phase noise. Comparative measurements show that, relative to a solid-core polarization-maintaining fiber (PMF) interferometer, the HC-PBGF interferometer achieves an ∼18 dB reduction in phase-noise power spectral density (PSD) in the mHz-Hz band while maintaining an ∼7 dB advantage in the Hz-k Hz band, which is qualitatively consistent with the simplified theoretical prediction. These results support the development of HC-PBGF-based broadband low-noise fiber interferometry.