A Simple Optical Sensor Based on an In-Line Mach–Zehnder Interferometer for Monitoring Single- and Two-Phase Flows in Pipelines

In this article, we proposed a simple optical sensor for flow measurement. The sensor structure is based on an in-line Mach-Zehnder interferometer formed by splicing an input single-mode fiber section and an output single-mode fiber section to a single-mode fiber sandwiched by two multimode fibers; it is called SMSMS sensor. The proposed sensor presents a high sensitivity due to low order modes that propagate in the middle single-mode fiber (SMF) cladding. The sensor is experimentally investigated and validated in which the results show good agreement between the optical power and flow for monitoring single- and two-phase flows using water and air fluids. Using this sensor, it is possible to identify the presence of air in the pipeline, in addition to the identification of the flow pattern. Thus, the proposed sensor is an interesting alternative for measuring single- and two-phase flows.