High Spatial Resolution Temperature Sensing Determined by Sampling Spacing With RDTS System

Raman distributed temperature sensing (RDTS) systems monitor temperature variation regions (TVRs) that are less than the shortest fiber length required to accurately measure the temperature, and using conventional temperature demodulation methods will result in inaccurate temperature measurements. The most cost-effective solution is to construct the relation curve between the temperature and the characteristics of the temperature rise curve for different TVR lengths, but this increases the workload of temperature calibration, and the unstable linearity in the relation curves constructed under the measured TVR lengths will bring errors to the temperature demodulation. To solve this problem, this article proposes to use the Raman intensity of each sampling point in the temperature rise curve to construct a temperature rise curve with a spatial resolution of the length and use the maximum intensity of the reconstructed temperature rise curve to calibrate with the temperature at one time to realize the temperature sensing of the TVR with a length of centimeter scale. The experimental results well demonstrate that the proposed method can accurately realize the temperature sensing of TVR with a length of 30 cm with a temperature error of ±0.73 °C. The proposed method allows accurate monitoring of anomalous temperatures of TVRs of arbitrary length, such as fires, through a high spatial resolution determined by the sampling spacing without changing the internal structure of a conventional RDTS system.

I. Introduction

The sensing fiber in Raman distributed temperature sensing (RDTS) system can be equated to thousands of discrete sensing units, thus greatly simplifying sensor installation and readout, and the passivity of the sensing fiber allows RDTS systems to monitor temperature in explosive as well as highly electromagnetic environments [1], [2], [3], [4], [5], [6], [7] and has promising applications in urban safety monitoring [8], submarine subsurface temperature mapping [9], [10], [11], detection and prevention of underground cables [12], [13], [14], and tunnel temperature measurement [15], [16].