Pressure-typed flowmeter based on Ʊ-typed few-mode fiber with temperature self-correction

In this paper, an optical fiber sensor with flexible skin is introduced for measuring liquid velocity and temperature. The sensor is composed of polyurethane membrane and Ʊ-typed few-mode fiber (FMF). By converting the change in liquid velocity into the pressure change borne by the polyurethane diaphragm, the interference spectrum shifts due to micro deformation of the Ʊ-typed FMF. The research results indicate that the sensitivity of the liquid velocity sensor is 0.545 nm/(m/s). At the same time, we proposed a temperature self-decoupling scheme, and solved the cross-sensitivity problem by discussing the influence of temperature on the double interference dips. The temperature measurement compensation accuracy can reach 0.348 nm/°C。Finally, we conducted experiments by placing the sensor in an actual pipeline, and the results showed that the sensor has excellent mechanical properties and thermal stability. This work is beneficial for exploring compact and high-sensitivity fiber optic flow velocity detection methods.