This research investigates the water immersion phenomenon in hollow-core anti-resonant fibers (HC-ARF) following structural damage under real-world conditions, such as outdoor deployment, conduit breach, or accidental damage, and its subsequent effects on transmission performance. The study aims to elucidate the water immersion mechanism and establish the temporal relationship between water penetration depth and duration through experimental measurements. Additionally, this research quantifies the impact of water immersion on signal attenuation. Understanding these dynamics and their implications is crucial for evaluating HC-ARF’s long-term reliability, failure modes, and maintenance requirements in practical applications, while also informing improvements in environmental resilience design. These insights are essential for ensuring operational stability and predicting the longevity of optical communication and sensing systems.

This investigation comprises three interconnected phases—theoretical simulation, experimental measurement, and performance testing—to analyze water immersion dynamics in fractured HC-ARF and associated transmission degradation mechanisms. The theoretical simulation utilizes the Washburn capillary imbibition equation Lt=γ?r?cosθ2η?t to model water immersion dynamics in HC-ARF microtubes. The depth-time relationships are derived by varying surface tension γ, viscosity η, equivalent tube diameter r, and contact angle θ. The experimental phase involves immersing HC-ARF sample end-faces of various lengths in water under ambient conditions, with depth-time data recorded throughout immersion. Comparative analysis of experimental and theoretical results across different fiber lengths and immersion conditions reveals key factors influencing water immersion behavior. The performance evaluation examines attenuation effects using long-length fiber samples subjected to fracture-immersion treatment (192 h). The methodology involves sequential excision of the water-contaminated segment while recording output spectra, followed by removal of multiple redundant segments with spectral documentation after each cut. All spectra are captured using a broadband source and optical spectrum analyzer, with attenuation spectra measured via the cut-back method.

Theoretical simulations based on the Washburn equation, adapted to the specific fiber structure, produce water immersion depth-time curves and predict final immersion depths under various initial gas pressures. Experimental data indicate that internal gas pressure is the primary determinant of immersion kinetics. During 192 h of immersion testing, all 10 m samples demonstrate final immersion depths exceeding 9.5 m, with immersion velocity decreasing under end-face sealing conditions due to pressure accumulation from gas compression. Longer fibers (0.5 km and 1.0 km samples) exhibit similar depth-time patterns, reaching approximately 36 m immersion depth after 192 h, though variations from simulations suggest structural non-uniformities. Attenuation analysis reveals that complete performance restoration requires removing both the water-contaminated segment and an additional 2 m redundancy section. Given the consistent cross-sectional geometry, internal pressure conditions, and non-optimal baseline attenuation across tested samples, further validation with diverse fiber types remains necessary to establish comprehensive dynamic models and degradation principles.

This research combines theoretical modeling with experimental validation to examine water immersion dynamics in HC-ARF and resultant attenuation effects. The Washburn equation-based theoretical depth-time correlations are confirmed through systematic immersion experiments across various fiber lengths, demonstrating that immersion velocity depends primarily on internal gas pressure and fiber geometry, reaching maximum rates during single-end sealed immersion. Extended fibers of 0.5 km and 1.0 km demonstrate uniform 36 m immersion depths after 192 h, while removing 2 m beyond maximum immersion depth effectively restores baseline attenuation. Variations between experimental and theoretical results suggest structural non-uniformities, leading to a practical recommendation of removing contaminated segments plus 2 m redundancy sections to remediate post-fracture water damage.