Active Heating-Based Distributed Fiber-Optic Sensing for Groundwater Characterization

Abstract

Distributed fiber-optic sensing (DFOS) has rapidly advanced across many engineering fields, offering significant advantages for slope and groundwater monitoring. This study demonstrates the application of a phase noise–compensated optical frequency-domain reflectometry (PNC-OFDR) method for characterizing subsurface hydrologic features in turbiditic fractured aquifers. Heating and temperature-sensing cables installed in a cement-grouted borehole enabled high-resolution thermal monitoring under controlled heating. Analysis of thermal responses revealed several groundwater flow and high-saturation zones. Depth-dependent variations reflected lithological heterogeneity, while recovery (cooling) data proved crucial for identifying water-bearing zones and estimating thermal properties. Field results agreed well with laboratory thermal conductivity, confirming AH-DFOS as an effective tool for high-resolution and reliable detection of active groundwater pathways.