Distance-independent high spatial resolution distributed optical fiber sensing utilizing incoherent Raman OFDR

The spatial resolution of conventional Raman distributed optical fiber sensing (RDOFS) systems is fundamentally constrained by the physics principle of optical time domain reflection, which emerges as the primary theoretical limitation. This inherent constraint manifests as progressive pulse broadening along extended sensing distances, confining current kilometer-scale RDOFS implementations to spatial resolutions ranging from several meters to tens of meters. To address this limitation, we proposed and experimentally demonstrated an innovative distributed optical fiber sensing scheme based on incoherent Raman optical frequency domain reflection (IROFDR) employing frequency-space transformation principles. Through systematic investigation of Raman backscattering characteristics generated by sinusoidally modulated laser signals with uniform direct-current-offset stepping along optical fibers, we established a novel optical sensing mechanism. The implemented system achieved breakthrough performance metrics: 10 km sensing distance with 50 cm spatial resolution (0.1 ℃ temperature accuracy), where spatial resolution demonstrates independence from sensing distance and shows deterministic dependence on maximum modulation frequency. This advancement provides a novel approach for high-resolution Raman distributed fiber sensing applications.