A hot-wire flowmeter based on polymer-filled extrinsic-phase-shift fiber Bragg grating

A polymer-filled extrinsic-phase-shift fiber Bragg grating (EPS-FBG) sensor for flow measurement is proposed. The EPS-FBG is obtained by cutting a common FBG to form a micron gap and filling it with epoxy resin polymer, and the reflection spectrum shows a phase shift peak with a very narrow bandwidth different from that of FBG. The phase shift peak of the EPS-FBG has a high-temperature sensitivity of 28.3 pm/°C, and the linearity of temperature is 0.996, which makes it possible to exhibit excellent for measuring temperature and improve any sensor that takes temperature measurements. The phase shift peak of the proposed flowmeter with active heating shifts with variations in flow, the flow measurement is realized by monitoring the wavelength change of the phase shift peak. Experiments have been conducted in the range of 300–4000 L/h and confirmed that the flowmeter exhibits compliance of more than 0.998 for specific non-linear functions at different powers, which enables an accurate theoretical calculation. At a heating power of 33 W, the average sensitivity of the flowmeter was measured to be 12 L/h/pm, and at lower flow rates the sensitivity was up to 1 pm/L/h, which indicates that the EPS-FBG hot-wire flowmeter has potential for micro-flow measurement applications. Moreover, the proposed flowmeter has the merits of easy fabrication and low cost, and is expected to be widely used in the industry.