Distributed temperature sensing with unmodified coaxial cable based on random reflections in TDR signal

This paper presents a new method to utilize an unmodified coaxial cable for distributed temperature sensing. It compares the time domain reflectometry (TDR) signal before and after temperature change by cross-correlation, and the resultant time delay will indicate the region as well as the magnitude of the temperature change. The temperature change from 27 °C to 70 °C is monitored and a linear relationship between the cross-correlation value and temperature can be observed. Two-section temperature change monitoring is also demonstrated to show its distributed sensing capability. This method is more sensitive than the traditional TDR method. Compared to coaxial cable sensors based on multiple Fabry–Perot interferometers or coaxial cable Bragg gratings, the cable does not need to be modified before installation, and it is truly distributed sensing without dark zone.