This chapter explores the application of distributed temperature sensing (DTS) technology in geothermal exploration, focusing on its ability to monitor transient and transitional temperature phenomena during events such as water injection or cessation within geothermal wells. Using Raman scattering in optical fibers, DTS enables precise measurement of temperature variations over time, making it especially effective to identify location and property of highly permeable fractures. It enhances the characterization of reservoir properties, fluid flow, and fracture behavior, improving geothermal well management. Some of the technical challenges in QC issues are also addressed.