Temperature Sensing of Horizontal Liquid Flow by Optical Carrier-Based Microwave Interferometry

Long-distance pipeline temperature monitoring and measurement are vital for industrial production. In this article, a recently proposed microwave photonics technique, optical carrier-based microwave interferometry (OCMI), is applied to dynamic fluid temperature measurement, realizing distributed temperature sensing of horizontal liquid flow for the first time. The theory of OCMI-based temperature sensitivity is established, and factors affecting the temperature-induced thermal strain in a double-coated optical fiber (DCF) are explored through numerical simulations. By conducting experiments on a horizontal fluid circulation device, dynamic fluid temperature measurements based on the OCMI technique are demonstrated. The Fabry-Perot interferometer (FPI) placed on the outer wall of the organic glass pipeline has a linear response to temperature, providing accurate temperature measurements within an error of ±2.5%. The experimental results show that the OCMI technique is able to accurately measure the outer wall temperature, thus reflecting the temperature changes of horizontal liquid flow. More importantly, dynamic fluid temperature measurements achieved using FPIs of varying lengths reveal the potential of the OCMI technique for long-pipeline distributed temperature sensing in industrial sites. Overall, the successful application of the OCMI technique in fluid temperature measurements lays a solid foundation for future measurements of other flow parameters and brings a new technical approach and solution to multiphase flow testing.